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18 pages, 4332 KiB

Open AccessArticle

Brachypodium Antifreeze Protein Gene Products Inhibit Ice Recrystallisation, Attenuate Ice Nucleation, and Reduce Immune Response

by Collin L. Juurakko, George C. diCenzo and Virginia K. Walker

Plants 2022, 11(11), 1475; https://doi.org/10.3390/plants11111475 - 31 May 2022

Cited by 2 | Viewed by 3423

Abstract

Antifreeze proteins (AFPs) from the model crop, Brachypodium distachyon, allow freeze survival and attenuate pathogen-mediated ice nucleation. Intriguingly, Brachypodium AFP genes encode two proteins, an autonomous AFP and a leucine-rich repeat (LRR). We present structural models which indicate that ice-binding motifs on [...] Read more.

Antifreeze proteins (AFPs) from the model crop, Brachypodium distachyon, allow freeze survival and attenuate pathogen-mediated ice nucleation. Intriguingly, Brachypodium AFP genes encode two proteins, an autonomous AFP and a leucine-rich repeat (LRR). We present structural models which indicate that ice-binding motifs on the ~13 kDa AFPs can “spoil” nucleating arrays on the ~120 kDa bacterial ice nucleating proteins used to form ice at high sub-zero temperatures. These models are consistent with the experimentally demonstrated decreases in ice nucleating activity by lysates from wildtype compared to transgenic Brachypodium lines. Additionally, the expression of Brachypodium LRRs in transgenic Arabidopsis inhibited an immune response to pathogen flagella peptides (flg22). Structural models suggested that this was due to the affinity of the LRR domains to flg22. Overall, it is remarkable that the Brachypodium genes play multiple distinctive roles in connecting freeze survival and anti-pathogenic systems via their encoded proteins’ ability to adsorb to ice as well as to attenuate bacterial ice nucleation and the host immune response. Full article

(This article belongs to the Special Issue Plant Physiological, Biochemical, and Molecular Responses to Abiotic Stresses)

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16 pages, 2435 KiB

Open AccessArticle

Differential Responses to UV-A Stress Recorded in Carotenogenic Microalgae Haematococcus rubicundus, Bracteacoccus aggregatus, and Deasonia sp.

by Konstantin Chekanov, Karina Shibzukhova, Elena Lobakova and Alexei Solovchenko

Plants 2022, 11(11), 1431; https://doi.org/10.3390/plants11111431 - 27 May 2022

Cited by 7 | Viewed by 2755

Abstract

UV-A is the main ultraviolet component of natural (solar) radiation. Despite it, its effect on phototrophs is studied less than UV-B. Effects of UV-A on photosynthetic apparatus of three carotenoid-producing microalgae were elucidated. Photosynthetic activity was studied using chlorophyll fluorescence analysis. Cell extracts [...] Read more.

UV-A is the main ultraviolet component of natural (solar) radiation. Despite it, its effect on phototrophs is studied less than UV-B. Effects of UV-A on photosynthetic apparatus of three carotenoid-producing microalgae were elucidated. Photosynthetic activity was studied using chlorophyll fluorescence analysis. Cell extracts were evaluated by absorbance spectroscopy. On the one hand, there were some common features of three strains. In all cases the changes involved PSII primary photochemistry and antennae size. All strains accumulated UV-absorbing polar compounds. On the other hand, some responses were different. Upregulation of non-photochemical quenching was observed only in B. aggregatus BM5/15, whereas in other cases its level was low. H. rubicundus BM7/13 and Deasonia sp. NAMSU 934/2 accumulated secondary carotenoids, whereas B. aggregatus BM5/15 accumulated primary ones. Microscopic features of the cultures were also different. H. rubicundus BM7/13 and Deasonia sp. NAMSU 934/2 were represented mostly by solitaire cells or small cell clusters, lacking their green color; the cells of B. aggregatus BM5/15 formed aggregates from green cells. Cell aggregation could be considered as an additional UV-protecting mechanism. Finally, the strains differed by their viability. B. aggregatus BM5/15 was most resistant to UV-A, whereas massive cell death was observed in two other cultures. Full article

(This article belongs to the Special Issue Plant Physiological, Biochemical, and Molecular Responses to Abiotic Stresses)

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16 pages, 3737 KiB

Open AccessArticle

The R2R3 MYB Transcription Factor MYB71 Regulates Abscisic Acid Response in Arabidopsis

by Yuxin Cheng, Yanxing Ma, Na Zhang, Rao Lin, Yuan Yuan, Hainan Tian, Saddam Hussain, Siyu Chen, Wenting Yang, Ling Cai, Yingying Li, Xiaoping Wang, Tianya Wang and Shucai Wang

Plants 2022, 11(10), 1369; https://doi.org/10.3390/plants11101369 - 21 May 2022

Cited by 10 | Viewed by 2496

Abstract

Abscisic acid (ABA) regulates plant responses to abiotic stresses via regulating the expression of downstream genes, yet the functions of many ABA responsive genes remain unknown. We report here the characterization of MYB71, a R2R3 MYB transcription factor in regulating ABA responses [...] Read more.

Abscisic acid (ABA) regulates plant responses to abiotic stresses via regulating the expression of downstream genes, yet the functions of many ABA responsive genes remain unknown. We report here the characterization of MYB71, a R2R3 MYB transcription factor in regulating ABA responses in Arabidopsis. RT-PCR results show that the expression level of MYB71 was increased in response to ABA treatment. Arabidopsis protoplasts transfection results show that MYB71 was specifically localized in nucleus and it activated the Gal4:GUS reporter gene when recruited to the Gal4 promoter by a fused DNA binding domain GD. Roles of MYB71 in regulating plant response to ABA were analyzed by generating Arabidopsis transgenic plants overexpression MYB71 and gene edited mutants of MYB71. The results show that ABA sensitivity was increased in the transgenic plants overexpression MYB71, but decreased in the MYB71 mutants. By using a DEX inducible system, we further identified genes are likely regulated by MYB71, and found that they are enriched in biological process to environmental stimuli including abiotic stresses, suggesting that MYB71 may regulate plant response to abiotic stresses. Taken together, our results suggest that MYB71 is an ABA responsive gene, and MYB71 functions as a transcription activator and it positively regulates ABA response in Arabidopsis. Full article

(This article belongs to the Special Issue Plant Physiological, Biochemical, and Molecular Responses to Abiotic Stresses)

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14 pages, 1831 KiB

Open AccessArticle

Exogenous Rosmarinic Acid Application Enhances Thermotolerance in Tomatoes

by Zhiwen Zhou, Jiajia Li, Changan Zhu, Beiyu Jing, Kai Shi, Jingquan Yu and Zhangjian Hu

Plants 2022, 11(9), 1172; https://doi.org/10.3390/plants11091172 - 26 Apr 2022

Cited by 7 | Viewed by 2357

Abstract

Due to global warming, high-temperature stress has become a major threat to plant growth and development, which causes a severe challenge to food security worldwide. Therefore, it is necessary to explore the plant bioactive molecules, which could be a promising approach to strengthening [...] Read more.

Due to global warming, high-temperature stress has become a major threat to plant growth and development, which causes a severe challenge to food security worldwide. Therefore, it is necessary to explore the plant bioactive molecules, which could be a promising approach to strengthening plant thermotolerance. Rosmarinic acid (RA) serves as a plant-derived phenolic compound and has beneficial and health-promoting effects for human beings. However, the involvement of RA in plant stress response and the underlying molecular mechanism was largely unknown. In this study, we found that exogenous RA application conferred improved thermotolerance in tomatoes. The transcript abundance and the enzyme activity of enzymatic antioxidants, such as ascorbate peroxidase (APX), catalase (CAT), glutathione reductase (GR), and dehydroascorbate reductase (DHAR), were further promoted by RA treatment in tomato plants subjected to high-temperature stress. Moreover, RA activated the antioxidant system and modulated the cellular redox homeostasis also associated with the redox status of nonenzymatic glutathione and ascorbic acid. The results of RNA-seq data showed that transcriptional regulation was involved in RA-mediated thermotolerance. Consistently, the gene expression of several high temperature-responsive transcription factors like HsfA2, and WRKY family genes were substantially induced by RA treatment, which potentially contributed to the induction of heat shock proteins (HSPs). Overall, these findings not only gave a direct link between RA and plant thermotolerance but also provided an attractive approach to protecting crop plants from high-temperature damage in a global warming future. Full article

(This article belongs to the Special Issue Plant Physiological, Biochemical, and Molecular Responses to Abiotic Stresses)

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13 pages, 811 KiB

Open AccessArticle

Morpho-Physiological Responses of Two Multipurpose Species from the Tropical Dry Forest to Contrasting Light Levels: Implications for Their Nursery and Field Management

by Erickson Basave-Villalobos, Víctor M. Cetina-Alcalá, Víctor Conde-Martínez, Miguel Á. López-López, Carlos Trejo and Carlos Ramírez-Herrera

Plants 2022, 11(8), 1042; https://doi.org/10.3390/plants11081042 - 12 Apr 2022

Cited by 1 | Viewed by 2295

Abstract

Understanding the responses that some plants exhibit to acclimatize and thrive in different light environments can serve as a guideline to optimize their production or establishment. Morpho-physiological changes in Crescentia alata and Enterolobium cyclocarpum were examined in response to varying light levels: 25%, [...] Read more.

Understanding the responses that some plants exhibit to acclimatize and thrive in different light environments can serve as a guideline to optimize their production or establishment. Morpho-physiological changes in Crescentia alata and Enterolobium cyclocarpum were examined in response to varying light levels: 25%, 35%, 55% and 70% of photosynthetic photon flux density (PPFD) of total solar radiation. One-month-old seedlings were subjected to the light treatments; subsequently, the effects on morphology, photosynthetic capacity, nutrient status, non-structural carbohydrate reserves (NSC) and growth were evaluated in three-month-old seedlings. Light levels affected several morpho-physiological parameters. C. alata responded better to higher light levels and E. cyclocarpum to lower levels. Particularly, C. alata with 70% PPFD increased its size in height and diameter, and accumulated more biomass in leaves, stems, and roots; it also exhibited higher net assimilation rates, improved nitrogen and phosphorus status and growth. In contrast, E. cyclocarpum with 25% PPFD increased aboveground biomass, nitrogen levels and NSC in leaves. Both species show morpho-physiological changes that determine their ability to acclimatize to different light conditions. This serves as a basis for designing better management strategies in the nursery or field by defining the light environments conducive to a proper functioning. Full article

(This article belongs to the Special Issue Plant Physiological, Biochemical, and Molecular Responses to Abiotic Stresses)

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22 pages, 6913 KiB

Open AccessArticle

Synergistic Modulation of Seed Metabolites and Enzymatic Antioxidants Tweaks Moisture Stress Tolerance in Non-Cultivated Traditional Rice Genotypes during Germination

by Asish Kanakaraj Binodh, Sugitha Thankappan, Anupriya Ravichandran, Debasis Mitra, Senthil Alagarsamy, Periyasamy Panneerselvam, Ansuman Senapati, Rokayya Sami, Amina A. M. Al-Mushhin, Amani H. Aljahani, Amal Alyamani and Mohammed Alqurashi

Plants 2022, 11(6), 775; https://doi.org/10.3390/plants11060775 - 14 Mar 2022

Cited by 8 | Viewed by 2553

Abstract

Traditional rice landraces are treasures for novel genes to develop climate-resilient cultivars. Seed viability and germination determine rice productivity under moisture stress. The present study evaluated 100 rice genotypes, including 85 traditional landraces and 15 improved cultivars from various agro-ecological zones of Tamil [...] Read more.

Traditional rice landraces are treasures for novel genes to develop climate-resilient cultivars. Seed viability and germination determine rice productivity under moisture stress. The present study evaluated 100 rice genotypes, including 85 traditional landraces and 15 improved cultivars from various agro-ecological zones of Tamil Nadu, along with moisture-stress-susceptible (IR 64) and moisture-stress-tolerant (IR 64 Drt1) checks. The landraces were screened over a range of osmotic potentials, namely (−) 1.0 MPa, (−) 1.25 MPa and (−) 1.5 MPa, for a period of 5 days in PEG-induced moisture stress. Physio-morphological traits, such as rate of germination, root and shoot length, vigor index, R/S ratio and relative water content (RWC), were assessed during early moisture stress at the maximum OP of (−) 1.5 MPa. The seed macromolecules, phytohormones (giberellic acid, auxin (IAA), cytokinin and abscisic acid), osmolytes and enzymatic antioxidants (catalase and superoxide dismutase) varied significantly between moisture stress and control treatments. The genotype Kuliyadichan registered more IAA and giberellic acid (44% and 35%, respectively, over moisture-stress-tolerant check (IR 64 Drt1), whereas all the landraces showed an elevated catalase activity, thus indicating that the tolerant landraces effectively eliminate oxidative damages. High-performance liquid chromatography analysis showed a reduction in cytokinin and an increase in ABA level under induced moisture stress. Hence, the inherent moisture-stress tolerance of six traditional landraces, such as Kuliyadichan, Rajalakshmi, Sahbhagi Dhan, Nootripathu, Chandaikar and Mallikar, was associated with metabolic responses, such as activation of hydrolytic enzymes, hormonal crosstalk, ROS signaling and antioxidant enzymes (especially catalase), when compared to the susceptible check, IR 64. Hence, these traditional rice landraces can serve as potential donors for introgression or pyramiding moisture-stress-tolerance traits toward developing climate-resilient rice cultivars. Full article

(This article belongs to the Special Issue Plant Physiological, Biochemical, and Molecular Responses to Abiotic Stresses)

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26 pages, 4870 KiB

Open AccessArticle

Comparative Phenotyping of Two Commonly Used Chlamydomonas reinhardtii Background Strains: CC-1690 (21gr) and CC-5325 (The CLiP Mutant Library Background)

by Ningning Zhang, Leila Pazouki, Huong Nguyen, Sigrid Jacobshagen, Brae M. Bigge, Ming Xia, Erin M. Mattoon, Anastasiya Klebanovych, Maria Sorkin, Dmitri A. Nusinow, Prachee Avasthi, Kirk J. Czymmek and Ru Zhang

Plants 2022, 11(5), 585; https://doi.org/10.3390/plants11050585 - 22 Feb 2022

Cited by 9 | Viewed by 4570

Abstract

The unicellular green alga Chlamydomonas reinhardtii is an excellent model organism to investigate many essential cellular processes in photosynthetic eukaryotes. Two commonly used background strains of Chlamydomonas are CC-1690 and CC-5325. CC-1690, also called 21gr, has been used for the Chlamydomonas genome project [...] Read more.

The unicellular green alga Chlamydomonas reinhardtii is an excellent model organism to investigate many essential cellular processes in photosynthetic eukaryotes. Two commonly used background strains of Chlamydomonas are CC-1690 and CC-5325. CC-1690, also called 21gr, has been used for the Chlamydomonas genome project and several transcriptome analyses. CC-5325 is the background strain for the Chlamydomonas Library Project (CLiP). Photosynthetic performance in CC-5325 has not been evaluated in comparison with CC-1690. Additionally, CC-5325 is often considered to be cell-wall deficient, although detailed analysis is missing. The circadian rhythms in CC-5325 are also unclear. To fill these knowledge gaps and facilitate the use of the CLiP mutant library for various screens, we performed phenotypic comparisons between CC-1690 and CC-5325. Our results showed that CC-5325 grew faster heterotrophically in dark and equally well in mixotrophic liquid medium as compared to CC-1690. CC-5325 had lower photosynthetic efficiency and was more heat-sensitive than CC-1690. Furthermore, CC-5325 had an intact cell wall which had comparable integrity to that in CC-1690 but appeared to have reduced thickness. Additionally, CC-5325 could perform phototaxis, but could not maintain a sustained circadian rhythm of phototaxis as CC1690 did. Finally, in comparison to CC-1690, CC-5325 had longer cilia in the medium with acetate but slower swimming speed in the medium without nitrogen and acetate. Our results will be useful for researchers in the Chlamydomonas community to choose suitable background strains for mutant analysis and employ the CLiP mutant library for genome-wide mutant screens under appropriate conditions, especially in the areas of photosynthesis, thermotolerance, cell wall, and circadian rhythms. Full article

(This article belongs to the Special Issue Plant Physiological, Biochemical, and Molecular Responses to Abiotic Stresses)

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17 pages, 3716 KiB

Open AccessArticle

Water Stress Alters Morphophysiological, Grain Quality and Vegetation Indices of Soybean Cultivars

by Cássio Jardim Tavares, Walter Quadros Ribeiro Junior, Maria Lucrecia Gerosa Ramos, Lucas Felisberto Pereira, Raphael Augusto das Chagas Noqueli Casari, André Ferreira Pereira, Carlos Antonio Ferreira de Sousa, Anderson Rodrigo da Silva, Sebastião Pedro da Silva Neto and Liliane Marcia Mertz-Henning

Plants 2022, 11(4), 559; https://doi.org/10.3390/plants11040559 - 21 Feb 2022

Cited by 18 | Viewed by 3233

Abstract

Rainfall is among the climatic factors that most affect production, as in the Brazilian Cerrado. Non-destructive and automated phenotyping methods are fast and efficient for genotype selection. The objective of this work was to evaluate, under field conditions, the morphophysiological changes, yield, and [...] Read more.

Rainfall is among the climatic factors that most affect production, as in the Brazilian Cerrado. Non-destructive and automated phenotyping methods are fast and efficient for genotype selection. The objective of this work was to evaluate, under field conditions, the morphophysiological changes, yield, and grain quality of soybean (Glycine max L. Merrill) under water stress in the Brazilian Cerrado. The plots comprised six soybean cultivars and the subplots of four water regimes, corresponding to 31, 44, 64 and 100% of crop evapotranspiration replacement. The experiments were conducted from May to September 2018 and 2019. An irrigation system with a bar of sprinklers with different flow rates was used. Gas exchange, vegetation indices (measured using a hyperspectral sensor embedded in a drone), yield and grain quality were evaluated. Water stress had different effects on gas exchange, vegetation indices, grain yield and chemical composition among the cultivars. Embrapa cultivar BRS 7280 Roundup ready (RR) and Nidera cultivar NA 5909 RG (glyphosate resistant) are yield stable and have a greater tolerance to drought. BRS 7280RR showed a higher tolerance to drought and higher water use efficiency (WUE) than all other tested cultivars. Vegetation indices, such as the NDVI (Normalized Difference Vegetation Index), correlated with the morphophysiological traits, such as plant height, were the most responsive variables to water stress. The NDVI can be used to predict soybean yield as a tool in a selection program under drought. Full article

(This article belongs to the Special Issue Plant Physiological, Biochemical, and Molecular Responses to Abiotic Stresses)

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21 pages, 4831 KiB

Open AccessArticle

Genome-Wide Analyses of Aspartic Proteases on Potato Genome (Solanum tuberosum): Generating New Tools to Improve the Resistance of Plants to Abiotic Stress

by Natalia Sigrid Norero, María Florencia Rey Burusco, Sebastián D’Ippólito, Cecilia Andrea Décima Oneto, Gabriela Alejandra Massa, Martín Alfredo Castellote, Sergio Enrique Feingold and María Gabriela Guevara

Plants 2022, 11(4), 544; https://doi.org/10.3390/plants11040544 - 18 Feb 2022

Cited by 4 | Viewed by 3310

Abstract

Aspartic proteases are proteolytic enzymes widely distributed in living organisms and viruses. Although they have been extensively studied in many plant species, they are poorly described in potatoes. The present study aimed to identify and characterize S. tuberosum aspartic proteases. Gene structure, chromosome [...] Read more.

Aspartic proteases are proteolytic enzymes widely distributed in living organisms and viruses. Although they have been extensively studied in many plant species, they are poorly described in potatoes. The present study aimed to identify and characterize S. tuberosum aspartic proteases. Gene structure, chromosome and protein domain organization, phylogeny, and subcellular predicted localization were analyzed and integrated with RNAseq data from different tissues, organs, and conditions focused on abiotic stress. Sixty-two aspartic protease genes were retrieved from the potato genome, distributed in 12 chromosomes. A high number of intronless genes and segmental and tandem duplications were detected. Phylogenetic analysis revealed eight StAP groups, named from StAPI to StAPVIII, that were differentiated into typical (StAPI), nucellin-like (StAPIIIa), and atypical aspartic proteases (StAPII, StAPIIIb to StAPVIII). RNAseq data analyses showed that gene expression was consistent with the presence of cis-acting regulatory elements on StAP promoter regions related to water deficit. The study presents the first identification and characterization of 62 aspartic protease genes and proteins on the potato genome and provides the baseline material for functional gene determinations and potato breeding programs, including gene editing mediated by CRISPR. Full article

(This article belongs to the Special Issue Plant Physiological, Biochemical, and Molecular Responses to Abiotic Stresses)

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21 pages, 5060 KiB

Open AccessEditor’s ChoiceArticle

Metabolic Circuits in Sap Extracts Reflect the Effects of a Microbial Biostimulant on Maize Metabolism under Drought Conditions

by Kgalaletso Othibeng, Lerato Nephali, Akhona Myoli, Nombuso Buthelezi, Willem Jonker, Johan Huyser and Fidele Tugizimana

Plants 2022, 11(4), 510; https://doi.org/10.3390/plants11040510 - 14 Feb 2022

Cited by 9 | Viewed by 3123

Abstract

The use of microbial biostimulants in the agricultural sector is increasingly gaining momentum and drawing scientific attention to decode the molecular interactions between the biostimulants and plants. Although these biostimulants have been shown to improve plant health and development, the underlying molecular phenomenology [...] Read more.

The use of microbial biostimulants in the agricultural sector is increasingly gaining momentum and drawing scientific attention to decode the molecular interactions between the biostimulants and plants. Although these biostimulants have been shown to improve plant health and development, the underlying molecular phenomenology remains enigmatic. Thus, this study is a metabolomics work to unravel metabolic circuits in sap extracts from maize plants treated with a microbial biostimulant, under normal and drought conditions. The biostimulant, which was a consortium of different Bacilli strains, was applied at the planting stage, followed by drought stress application. The maize sap extracts were collected at 5 weeks after emergence, and the extracted metabolites were analyzed on liquid chromatography-mass spectrometry platforms. The acquired data were mined using chemometrics and bioinformatics tools. The results showed that under both well-watered and drought stress conditions, the application of the biostimulant led to differential changes in the profiles of amino acids, hormones, TCA intermediates, phenolics, steviol glycosides and oxylipins. These metabolic changes spanned several biological pathways and involved a high correlation of the biochemical as well as structural metabolic relationships that coordinate the maize metabolism. The hypothetical model, postulated from this study, describes metabolic events induced by the microbial biostimulant for growth promotion and enhanced defences. Such understanding of biostimulant-induced changes in maize sap pinpoints to the biochemistry and molecular mechanisms that govern the biostimulant–plant interactions, which contribute to ongoing efforts to generate actionable knowledge of the molecular and physiological mechanisms that define modes of action of biostimulants. Full article

(This article belongs to the Special Issue Plant Physiological, Biochemical, and Molecular Responses to Abiotic Stresses)

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17 pages, 1570 KiB

Open AccessArticle

Interaction between Growth Regulators Controls In Vitro Shoot Multiplication in Paulownia and Selection of NaCl-Tolerant Variants

by Jehan Salem, Ahmed Hassanein, Deiaa A. El-Wakil and Naglaa Loutfy

Plants 2022, 11(4), 498; https://doi.org/10.3390/plants11040498 - 11 Feb 2022

Cited by 9 | Viewed by 3569

Abstract

The interaction between cytokinin, auxin and GA controlled in vitro shoot multiplication in paulownia was influenced by a medium water potential (Ψ) modulation, where it was modulated using different textures or strengths of MS medium, media of different types (MS, WPM, SH and [...] Read more.

The interaction between cytokinin, auxin and GA controlled in vitro shoot multiplication in paulownia was influenced by a medium water potential (Ψ) modulation, where it was modulated using different textures or strengths of MS medium, media of different types (MS, WPM, SH and B5) or NaCl incorporation. The interaction between 2 mg/L BAP and 0.1 mg/L NAA expressed the highest shoot number on each media type, but it was better with media of lower water potential (MS and WPM), and MS medium was the best. Ψ of full-strength semisolid MS medium expressed the highest shoot multiplication. The opposite was detected when Ψ of MS medium was changed using half- or double-strength MS. Ψ of full-strength MS medium in semisolid form resulted in a valuable interaction between 2 mg/L BAP, 0.1 mg/L NAA and 0.1 mg/L GA, leading to efficient shoot formation, and it was associated with an increase in internode length and decrease in stem diameter, which facilitated obtaining synseeds with a high ability to convert. High genetic variation was recorded under long-term culture (14 subcultures). Polymorphism using the ISSR technique was higher than that of RAPD. A further increase in polymorphism was detected when NaCl was used, where five salt-tolerant lines were selected. Some salt-tolerant-selected lines showed one or more amplification products of a specific molecular weight that did not appear in the control. For example, with OPA-07 and OPG-02 RAPD primers, all the salt-tolerant-selected lines showed the appearance of amplification fragments (610 bp and 300 bp, respectively) that were not detected in control. Full article

(This article belongs to the Special Issue Plant Physiological, Biochemical, and Molecular Responses to Abiotic Stresses)

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18 pages, 4771 KiB

Open AccessArticle

Ethanol Treatment Enhances Physiological and Biochemical Responses to Mitigate Saline Toxicity in Soybean

by Ashim Kumar Das, Touhidur Rahman Anik, Md. Mezanur Rahman, Sanjida Sultana Keya, Md. Robyul Islam, Md. Abiar Rahman, Sharmin Sultana, Protik Kumar Ghosh, Sabia Khan, Tofayel Ahamed, Totan Kumar Ghosh, Lam Son-Phan Tran and Mohammad Golam Mostofa

Plants 2022, 11(3), 272; https://doi.org/10.3390/plants11030272 - 20 Jan 2022

Cited by 27 | Viewed by 4607

Abstract

Soil salinity, a major environmental concern, significantly reduces plant growth and production all around the world. Finding solutions to reduce the salinity impacts on plants is critical for global food security. In recent years, the priming of plants with organic chemicals has shown [...] Read more.

Soil salinity, a major environmental concern, significantly reduces plant growth and production all around the world. Finding solutions to reduce the salinity impacts on plants is critical for global food security. In recent years, the priming of plants with organic chemicals has shown to be a viable approach for the alleviation of salinity effects in plants. The current study examined the effects of exogenous ethanol in triggering salinity acclimatization responses in soybean by investigating growth responses, and numerous physiological and biochemical features. Foliar ethanol application to saline water-treated soybean plants resulted in an enhancement of biomass, leaf area, photosynthetic pigment contents, net photosynthetic rate, shoot relative water content, water use efficiency, and K⁺ and Mg²⁺ contents, leading to improved growth performance under salinity. Salt stress significantly enhanced the contents of reactive oxygen species (ROS), malondialdehyde, and electrolyte leakage in the leaves, suggesting salt-induced oxidative stress and membrane damage in soybean plants. In contrast, ethanol treatment of salt-treated soybean plants boosted ROS-detoxification mechanisms by enhancing the activities of antioxidant enzymes, including peroxidase, ascorbate peroxidase, catalase, and glutathione S-transferase. Ethanol application also augmented the levels of proline and total free amino acids in salt-exposed plants, implying a role of ethanol in maintaining osmotic adjustment in response to salt stress. Notably, exogenous ethanol decreased Na⁺ uptake while increasing K⁺ and Mg²⁺ uptake and their partitioning to leaves and roots in salt-stressed plants. Overall, our findings reveal the protective roles of ethanol against salinity in soybean and suggest that the use of this cost-effective and easily accessible ethanol in salinity mitigation could be an effective approach to increase soybean production in salt-affected areas. Full article

(This article belongs to the Special Issue Plant Physiological, Biochemical, and Molecular Responses to Abiotic Stresses)

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19 pages, 3136 KiB

Open AccessEditor’s ChoiceArticle

Down-Regulation of Cytokinin Receptor Gene SlHK2 Improves Plant Tolerance to Drought, Heat, and Combined Stresses in Tomato

by Naveed Mushtaq, Yong Wang, Junmiao Fan, Yi Li and Jing Ding

Plants 2022, 11(2), 154; https://doi.org/10.3390/plants11020154 - 7 Jan 2022

Cited by 23 | Viewed by 3210

Abstract

Environmental stresses negatively affect the growth and development of plants. Several previous studies have elucidated the response mechanisms of plants to drought and heat applied separately; however, these two abiotic stresses often coincide in environmental conditions. The global climate change pattern has projected [...] Read more.

Environmental stresses negatively affect the growth and development of plants. Several previous studies have elucidated the response mechanisms of plants to drought and heat applied separately; however, these two abiotic stresses often coincide in environmental conditions. The global climate change pattern has projected that combined drought and heat stresses will tend to increase in the near future. In this study, we down-regulated the expression of a cytokinin receptor gene SlHK2 using RNAi and investigated the role of this gene in regulating plant responses to individual drought, heat, and combined stresses (drought + heat) in tomato. Compared to the wild-type (WT), SlHK2 RNAi plants exhibited fewer stress symptoms in response to individual and combined stress treatments. The enhanced abiotic stress tolerance of SlHK2 RNAi plants can be associated with increased membrane stability, osmoprotectant accumulation, and antioxidant enzyme activities. Furthermore, photosynthesis machinery was also protected in SlHK2 RNAi plants. Collectively, our results show that down-regulation of the cytokinin receptor gene SlHK2, and consequently cytokinin signaling, can improve plant tolerance to drought, heat, and combined stress. Full article

(This article belongs to the Special Issue Plant Physiological, Biochemical, and Molecular Responses to Abiotic Stresses)

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29 pages, 4643 KiB

Open AccessArticle

Deciphering Reserve Mobilization, Antioxidant Potential, and Expression Analysis of Starch Synthesis in Sorghum Seedlings under Salt Stress

by Himani Punia, Jayanti Tokas, Virender Singh Mor, Axay Bhuker, Anurag Malik, Nirmal Singh, Satpal, Abdulaziz Abdullah Alsahli and Daniel Ingo Hefft

Plants 2021, 10(11), 2463; https://doi.org/10.3390/plants10112463 - 15 Nov 2021

Cited by 24 | Viewed by 2628

Abstract

Salt stress is one of the major constraints affecting plant growth and agricultural productivity worldwide. Sorghum is a valuable food source and a potential model for studying and better understanding the salt stress mechanics in the cereals and obtaining a more comprehensive knowledge [...] Read more.

Salt stress is one of the major constraints affecting plant growth and agricultural productivity worldwide. Sorghum is a valuable food source and a potential model for studying and better understanding the salt stress mechanics in the cereals and obtaining a more comprehensive knowledge of their cellular responses. Herein, we examined the effects of salinity on reserve mobilization, antioxidant potential, and expression analysis of starch synthesis genes. Our findings show that germination percentage is adversely affected by all salinity levels, more remarkably at 120 mM (36% reduction) and 140 mM NaCl (46% reduction) than in the control. Lipid peroxidation increased in salt-susceptible genotypes (PC-5: 2.88 and CSV 44F: 2.93 nmloe/g.FW), but not in tolerant genotypes. SSG 59-3 increased activities of α-amylase, and protease enzymes corroborated decreased starch and protein content, respectively. SSG 59-3 alleviated adverse effects of salinity by suppressing oxidative stress (H₂O₂) and stimulating enzymatic and non-enzymatic antioxidant activities (SOD, APX, CAT, POD, GR, and GPX), as well as protecting cell membrane integrity (MDA, electrolyte leakage). A significant increase (p ≤ 0.05) was also observed in SSG 59-3 with proline, ascorbic acid, and total carbohydrates. Among inorganic cations and anions, Na⁺, Cl⁻, and SO₄²⁻ increased, whereas K⁺, Mg²⁺, and Ca²⁺ decreased significantly. SSG 59-3 had a less pronounced effect of excess Na⁺ ions on the gene expression of starch synthesis. Salinity also influenced Na+ ion efflux and maintained a lower cytosolic Na⁺/K⁺ ratio via concomitant upregulation of SbNHX-1 and SbVPPase-I ion transporter genes. Thus, we have highlighted that salinity physiologically and biochemically affect sorghum seedling growth. Based on these findings, we highlighted that SSG 59-3 performed better by retaining higher plant water status, antioxidant potential, and upregulation of ion transporter genes and starch synthesis, thereby alleviating stress, which may be augmented as genetic resources to establish sorghum cultivars with improved quality in saline soils. Full article

(This article belongs to the Special Issue Plant Physiological, Biochemical, and Molecular Responses to Abiotic Stresses)

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17 pages, 765 KiB

Open AccessArticle

The Relationships between Plant Developmental Traits and Winter Field Survival in Rye (Secale cereale L.)

by Hirbod Bahrani, Monica Båga, Jamie Larsen, Robert J. Graf, Andre Laroche and Ravindra N. Chibbar

Plants 2021, 10(11), 2455; https://doi.org/10.3390/plants10112455 - 13 Nov 2021

Cited by 6 | Viewed by 2822

Abstract

Overwintering cereals accumulate low temperature tolerance (LTT) during cold acclimation in the autumn. Simultaneously, the plants adjust to the colder season by making developmental changes at the shoot apical meristem. These processes lead to higher winter hardiness in winter rye varieties (Secale [...] Read more.

Overwintering cereals accumulate low temperature tolerance (LTT) during cold acclimation in the autumn. Simultaneously, the plants adjust to the colder season by making developmental changes at the shoot apical meristem. These processes lead to higher winter hardiness in winter rye varieties (Secale cereale L.) adapted to Northern latitudes as compared to other cereal crops. To dissect the winter-hardiness trait in rye, a panel of 96 genotypes of different origins and growth habits was assessed for winter field survival (WFS), LTT, and six developmental traits. Best Linear Unbiased Estimates for WFS determined from five field trials correlated strongly with LTT (r = 0.90, p < 0.001); thus, cold acclimation efficiency was the major contributor to WFS. WFS also correlated strongly (p < 0.001) with final leaf number (r = 0.80), prostrate growth habit (r = 0.61), plant height (r = 0.34), but showed weaker associations with top internode length (r = 0.30, p < 0.01) and days to anthesis (r = 0.25, p < 0.05). The heritability estimates (h²) for WFS-associated traits ranged from 0.45 (prostrate growth habit) to 0.81 (final leaf number) and were overall higher than for WFS (h² = 0.48). All developmental traits associated with WFS and LTT are postulated to be regulated by phytohormone levels at shoot apical meristem. Full article

(This article belongs to the Special Issue Plant Physiological, Biochemical, and Molecular Responses to Abiotic Stresses)

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13 pages, 1054 KiB

Open AccessArticle

The Combination of Increased Temperatures and High Irradiation Causes Changes in Photosynthetic Efficiency

by Antonela Markulj Kulundžić, Marija Viljevac Vuletić, Maja Matoša Kočar, Anto Mijić, Ivana Varga, Aleksandra Sudarić, Vera Cesar and Hrvoje Lepeduš

Plants 2021, 10(10), 2076; https://doi.org/10.3390/plants10102076 - 30 Sep 2021

Cited by 12 | Viewed by 2075

Abstract

Global warming and the associated climate change are imposing abiotic stress on plants. Abiotic factors are crucial for plant productivity, survival, and reproduction. Eight sunflower hybrids were tested in conditions of different water availability and with combinations of different temperatures and irradiation. The [...] Read more.

Global warming and the associated climate change are imposing abiotic stress on plants. Abiotic factors are crucial for plant productivity, survival, and reproduction. Eight sunflower hybrids were tested in conditions of different water availability and with combinations of different temperatures and irradiation. The changes in the photosynthetic efficiency were measured in the morning (control conditions: 2013, 25.8 °C and 349.1 W m⁻²; 2014, 21.8 °C and 296.4 W m⁻²) and afternoon (the combination of increased temperatures and high irradiation: 2013, 34 °C and 837.9 W m⁻²; 2014, 29.4 °C and 888.9 W m⁻²) at a flowering stage in rainfed or irrigated conditions. The measurement time (morning and afternoon conditions) had a statistically significant effect on all the tested parameters. The performance index (PI_ABS) in 2013 and the maximum quantum yield of photosystem II (TR₀/ABS) in 2014 are the only parameters significantly affected by the irrigation. As a result of the combined effect of increased temperatures and high irradiation, PI_ABS values decreased by 73–92% in rainfed conditions and by 63–87% in irrigated conditions in 2013, depending on the hybrid, while in 2014, the decrease varied between 70 and 86%. The TR₀/ABS decrease was 7–17% in 2013, depending on the hybrid, and 6–12% in 2014, both in rainfed and irrigated conditions. The principal component analysis confirmed the effect of the combination of increased temperatures and high irradiation on hybrids, sorting them exclusively according to the time of measurement. All investigated parameters highly fluctuated between hybrids but without observable trends for the morning and afternoon conditions, as well as for irrigation. Plants’ reaction to the combination of increased temperatures and high irradiation manifested as a change in their photosynthetic efficiency, i.e., the photosynthetic apparatus’ functioning was impaired. Full article

(This article belongs to the Special Issue Plant Physiological, Biochemical, and Molecular Responses to Abiotic Stresses)

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22 pages, 2033 KiB

Open AccessArticle

Foliar Application of Sodium Nitroprusside Boosts Solanum lycopersicum L. Tolerance to Glyphosate by Preventing Redox Disorders and Stimulating Herbicide Detoxification Pathways

by Cristiano Soares, Francisca Rodrigues, Bruno Sousa, Edgar Pinto, Isabel M. P. L. V. O. Ferreira, Ruth Pereira and Fernanda Fidalgo

Plants 2021, 10(9), 1862; https://doi.org/10.3390/plants10091862 - 9 Sep 2021

Cited by 12 | Viewed by 4106

Abstract

Strategies to minimize the effects of glyphosate (GLY), the most used herbicide worldwide, on non-target plants need to be developed. In this context, the current study was designed to evaluate the potential of nitric oxide (NO), provided as 200 µM sodium nitroprusside (SNP), [...] Read more.

Strategies to minimize the effects of glyphosate (GLY), the most used herbicide worldwide, on non-target plants need to be developed. In this context, the current study was designed to evaluate the potential of nitric oxide (NO), provided as 200 µM sodium nitroprusside (SNP), to ameliorate GLY (10 mg kg⁻¹ soil) phytotoxicity in tomato plants. Upon herbicide exposure, plant development was majorly inhibited in shoots and roots, followed by a decrease in flowering and fruit set; however, the co-application of NO partially prevented these symptoms, improving plant growth. Concerning redox homeostasis, lipid peroxidation (LP) and reactive oxygen species (ROS) levels rose in response to GLY in shoots of tomato plants, but not in roots. Additionally, GLY induced the overaccumulation of proline and glutathione, and altered ascorbate redox state, but resulted in the inhibition of the antioxidant enzymes. Upon co-treatment with NO, the non-enzymatic antioxidants were not particularly changed, but an upregulation of all antioxidant enzymes was found, which helped to keep ROS and LP under control. Overall, data point towards the benefits of NO against GLY in tomato plants by reducing the oxidative damage and stimulating detoxification pathways, while also preventing GLY-induced impairment of flowering and fruit fresh mass. Full article

(This article belongs to the Special Issue Plant Physiological, Biochemical, and Molecular Responses to Abiotic Stresses)

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10 pages, 1026 KiB

Open AccessArticle

Transcriptome Analysis of Arabidopsis thaliana Plants Treated with a New Compound Natolen128, Enhancing Salt Stress Tolerance

by Kaori Sako, Chien Van Ha, Akihiro Matsui, Maho Tanaka, Ayato Sato and Motoaki Seki

Plants 2021, 10(5), 978; https://doi.org/10.3390/plants10050978 - 14 May 2021

Cited by 4 | Viewed by 2998

Abstract

Salinity stress is a major threat to agriculture and global food security. Chemical priming is a promising approach to improving salinity stress tolerance in plants. To identify small molecules with the capacity to enhance salinity stress tolerance in plants, chemical screening was performed [...] Read more.

Salinity stress is a major threat to agriculture and global food security. Chemical priming is a promising approach to improving salinity stress tolerance in plants. To identify small molecules with the capacity to enhance salinity stress tolerance in plants, chemical screening was performed using Arabidopsis thaliana. We screened 6400 compounds from the Nagoya University Institute of Transformative Bio-Molecule (ITbM) chemical library and identified one compound, Natolen128, that enhanced salinity-stress tolerance. Furthermore, we isolated a negative compound of Natolen128, namely Necolen124, that did not enhance salinity stress tolerance, though it has a similar chemical structure to Natolen128. We conducted a transcriptomic analysis of Natolen128 and Necolen124 to investigate how Natolen128 enhances high-salinity stress tolerance. Our data indicated that the expression levels of 330 genes were upregulated by Natolen128 treatment compared with that of Necolen124. Treatment with Natolen128 increased expression of hypoxia-responsive genes including ethylene biosynthetic enzymes and PHYTOGLOBIN, which modulate accumulation of nitric oxide (NO) level. NO was slightly increased in plants treated with Natolen128. These results suggest that Natolen128 may regulate NO accumulation and thus, improve salinity stress tolerance in A. thaliana. Full article

(This article belongs to the Special Issue Plant Physiological, Biochemical, and Molecular Responses to Abiotic Stresses)

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20 pages, 3382 KiB

Open AccessArticle

Multivariate Analysis of Morpho-Physiological Traits Reveals Differential Drought Tolerance Potential of Bread Wheat Genotypes at the Seedling Stage

by Mohammed Mohi-Ud-Din, Md. Alamgir Hossain, Md. Motiar Rohman, Md. Nesar Uddin, Md. Sabibul Haque, Jalal Uddin Ahmed, Akbar Hossain, Mohamed M. Hassan and Mohammad Golam Mostofa

Plants 2021, 10(5), 879; https://doi.org/10.3390/plants10050879 - 27 Apr 2021

Cited by 50 | Viewed by 6417

Abstract

Drought is one of the foremost environmental stresses that can severely limit crop growth and productivity by disrupting various physiological processes. In this study, the drought tolerance potential of 127 diverse bread wheat genotypes was evaluated by imposing polyethylene glycol (PEG)-induced drought followed [...] Read more.

Drought is one of the foremost environmental stresses that can severely limit crop growth and productivity by disrupting various physiological processes. In this study, the drought tolerance potential of 127 diverse bread wheat genotypes was evaluated by imposing polyethylene glycol (PEG)-induced drought followed by multivariate analysis of several growth-related attributes. Results showed significant variations in the mean values of different morpho-physiological traits due to PEG-induced drought effects. Correlation analysis revealed that most of the studied traits were significantly correlated among them. The robust hierarchical co-clustering indicated that all the genotypes were clustered into four major groups, with cluster 4 (26 genotypes) being, in general, drought-tolerant followed by cluster 1 (19 genotypes) whereas, cluster 2 (55 genotypes) and 3 (27 genotypes) being drought-sensitive. Linear discriminant analysis (LDA) confirmed that around 90% of the genotypes were correctly assigned to clusters. Squared distance (D²) analysis indicated that the clusters differed significantly from each other. Principal component analysis (PCA) and genotype by trait biplot analysis showed that the first three components accounted for 71.6% of the total variation, with principal component (PC) 1 accounting for 35.4%, PC2 for 24.6% and PC3 for 11.6% of the total variation. Both PCA and LDA revealed that dry weights, tissue water content, cell membrane stability, leaf relative water content, root-shoot weight ratio and seedling vigor index played the most important discriminatory roles in explaining drought tolerance variations among 127 wheat genotypes. Our results conclude that the drought-tolerant and -sensitive wheat genotypes identified in this study would offer valuable genetic tools for further improvement of wheat productivity in arid and semi-arid regions during this time of unpredictable climate change. Full article

(This article belongs to the Special Issue Plant Physiological, Biochemical, and Molecular Responses to Abiotic Stresses)

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Review

Jump to: Research, Other

20 pages, 2147 KiB

Open AccessReview

Molecular and Physiological Perspectives of Abscisic Acid Mediated Drought Adjustment Strategies

by Abhilasha Abhilasha and Swarup Roy Choudhury

Plants 2021, 10(12), 2769; https://doi.org/10.3390/plants10122769 - 15 Dec 2021

Cited by 8 | Viewed by 4169

Abstract

Drought is the most prevalent unfavorable condition that impairs plant growth and development by altering morphological, physiological, and biochemical functions, thereby impeding plant biomass production. To survive the adverse effects, water limiting condition triggers a sophisticated adjustment mechanism orchestrated mainly by hormones that [...] Read more.

Drought is the most prevalent unfavorable condition that impairs plant growth and development by altering morphological, physiological, and biochemical functions, thereby impeding plant biomass production. To survive the adverse effects, water limiting condition triggers a sophisticated adjustment mechanism orchestrated mainly by hormones that directly protect plants via the stimulation of several signaling cascades. Predominantly, water deficit signals cause the increase in the level of endogenous ABA, which elicits signaling pathways involving transcription factors that enhance resistance mechanisms to combat drought-stimulated damage in plants. These responses mainly include stomatal closure, seed dormancy, cuticular wax deposition, leaf senescence, and alteration of the shoot and root growth. Unraveling how plants adjust to drought could provide valuable information, and a comprehensive understanding of the resistance mechanisms will help researchers design ways to improve crop performance under water limiting conditions. This review deals with the past and recent updates of ABA-mediated molecular mechanisms that plants can implement to cope with the challenges of drought stress. Full article

(This article belongs to the Special Issue Plant Physiological, Biochemical, and Molecular Responses to Abiotic Stresses)

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16 pages, 885 KiB

Open AccessReview

Problems and Prospects of Improving Abiotic Stress Tolerance and Pathogen Resistance of Oil Palm

by Lu Wei, Jerome Jeyakumar John Martin, Haiqing Zhang, Ruining Zhang and Hongxing Cao

Plants 2021, 10(12), 2622; https://doi.org/10.3390/plants10122622 - 29 Nov 2021

Cited by 7 | Viewed by 2918

Abstract

Oil palm crops are the most important determinant of the agricultural economy within the segment of oilseed crops. Oil palm growing in their natural habitats are often challenged simultaneously by multiple stress factors, both abiotic and biotic that limit crop productivity and are [...] Read more.

Oil palm crops are the most important determinant of the agricultural economy within the segment of oilseed crops. Oil palm growing in their natural habitats are often challenged simultaneously by multiple stress factors, both abiotic and biotic that limit crop productivity and are major constraints to meeting global food demands. The stress-tolerant oil palm crops that mitigate the effects of abiotic stresses on crop productivity are crucially needed to sustain agricultural production. Basal stem rot threatens the development of the industry, and the key to solving the problem is to breed new oil palm varieties resistant to adversity. This has created a need for genetic improvement which involves evaluation of germplasm, pest and disease resistance, earliness and shattering resistance, quality of oil, varieties for different climatic conditions, etc. In recent years, insights into physiology, molecular biology, and genetics have significantly enhanced our understanding of oil palm response towards such stimuli as well as the reason for varietal diversity in tolerance. In this review, we explore the research progress, existing problems, and prospects of oil palm stress resistance-based physiological mechanisms of stress tolerance as well as the genes and metabolic pathways that regulate stress response. Full article

(This article belongs to the Special Issue Plant Physiological, Biochemical, and Molecular Responses to Abiotic Stresses)

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14 pages, 332 KiB

Open AccessReview

Kosteletzkya pentacarpos: A Potential Halophyte Candidate for Phytoremediation in the Meta(loid)s Polluted Saline Soils

by Mingxi Zhou, Stanley Lutts and Ruiming Han

Plants 2021, 10(11), 2495; https://doi.org/10.3390/plants10112495 - 18 Nov 2021

Cited by 4 | Viewed by 2396

Abstract

Kosteletzkya pentacarpos (L.) Ledebour is a perennial facultative halophyte species from the Malvacea family that grows in coastal areas with high amounts of salt. The tolerance of K. pentacarpos to the high concentration of salt (0.5–1.5% salinity range of coastal saline land) has [...] Read more.

Kosteletzkya pentacarpos (L.) Ledebour is a perennial facultative halophyte species from the Malvacea family that grows in coastal areas with high amounts of salt. The tolerance of K. pentacarpos to the high concentration of salt (0.5–1.5% salinity range of coastal saline land) has been widely studied for decades. Nowadays, with the dramatic development of the economy and urbanization, in addition to the salt, the accumulation of mate(loid)s in coastal soil is increasing, which is threatening the survival of halophyte species as well as the balance of wetland ecosystems. Recently, the capacity of K. pentacarpos to cope with either single heavy metal stress or a combination of multiple meta(loid) toxicities was studied. Hence, this review focused on summarizing the physiological and biochemical behaviors of K. pentacarpos that has been simultaneously exposed to the combination of several meta(loid) toxicities. How the salt accumulated by K. pentacarpos impacts the response to meta(loid) stress was discussed. We conclude that as a potential candidate for phytoremediation, K. pentacarpos was able to cope with various environmental constrains such as multiple meta(loid) stresses due to its relative tolerance to meta(loid) toxicity. Full article

(This article belongs to the Special Issue Plant Physiological, Biochemical, and Molecular Responses to Abiotic Stresses)

Other

Jump to: Research, Review

16 pages, 3166 KiB

Open AccessBrief Report

Regulation of Nitrate (NO₃) Transporters and Glutamate Synthase-Encoding Genes under Drought Stress in Arabidopsis: The Regulatory Role of AtbZIP62 Transcription Factor

by Nkulu Kabange Rolly and Byung-Wook Yun

Plants 2021, 10(10), 2149; https://doi.org/10.3390/plants10102149 - 11 Oct 2021

Cited by 14 | Viewed by 3009

Abstract

Nitrogen (N) is an essential macronutrient, which contributes substantially to the growth and development of plants. In the soil, nitrate (NO₃) is the predominant form of N available to the plant and its acquisition by the plant involves several NO₃ [...] Read more.

Nitrogen (N) is an essential macronutrient, which contributes substantially to the growth and development of plants. In the soil, nitrate (NO₃) is the predominant form of N available to the plant and its acquisition by the plant involves several NO₃ transporters; however, the mechanism underlying their involvement in the adaptive response under abiotic stress is poorly understood. Initially, we performed an in silico analysis to identify potential binding sites for the basic leucine zipper 62 transcription factor (AtbZIP62 TF) in the promoter of the target genes, and constructed their protein–protein interaction networks. Rather than AtbZIP62, results revealed the presence of cis-regulatory elements specific to two other bZIP TFs, AtbZIP18 and 69. A recent report showed that AtbZIP62 TF negatively regulated AtbZIP18 and AtbZIP69. Therefore, we investigated the transcriptional regulation of AtNPF6.2/NRT1.4 (low-affinity NO₃ transporter), AtNPF6.3/NRT1.1 (dual-affinity NO₃ transporter), AtNRT2.1 and AtNRT2.2 (high-affinity NO₃ transporters), and AtGLU1 and AtGLU2 (both encoding glutamate synthase) in response to drought stress in Col-0. From the perspective of exploring the transcriptional interplay of the target genes with AtbZIP62 TF, we measured their expression by qPCR in the atbzip62 (lacking the AtbZIP62 gene) under the same conditions. Our recent study revealed that AtbZIP62 TF positively regulates the expression of AtPYD1 (Pyrimidine 1, a key gene of the de novo pyrimidine biosynthesis pathway know to share a common substrate with the N metabolic pathway). For this reason, we included the atpyd1-2 mutant in the study. Our findings revealed that the expression of AtNPF6.2/NRT1.4, AtNPF6.3/NRT1.1 and AtNRT2.2 was similarly regulated in atzbip62 and atpyd1-2 but differentially regulated between the mutant lines and Col-0. Meanwhile, the expression pattern of AtNRT2.1 in atbzip62 was similar to that observed in Col-0 but was suppressed in atpyd1-2. The breakthrough is that AtNRT2.2 had the highest expression level in Col-0, while being suppressed in atbzip62 and atpyd1-2. Furthermore, the transcript accumulation of AtGLU1 and AtGLU2 showed differential regulation patterns between Col-0 and atbzip62, and atpyd1-2. Therefore, results suggest that of all tested NO₃ transporters, AtNRT2.2 is thought to play a preponderant role in contributing to NO₃ transport events under the regulatory influence of AtbZIP62 TF in response to drought stress. Full article

(This article belongs to the Special Issue Plant Physiological, Biochemical, and Molecular Responses to Abiotic Stresses)

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