Search Results (45)

As a widely cultivated warm-season turfgrass, bermudagrass (Cynodon spp.) faces significant challenges in shaded environments due to its inherent low-light sensitivity. While improving photosynthetic adaptation represents a promising strategy to address this limitation, the associated regulatory mechanisms remain insufficiently characterized. In this study, we found that the overexpression of CdGLK1 significantly improved low-light tolerance in bermudagrass by increasing shoot weight, root weight, chlorophyll a, chlorophyll b, net photosynthetic rate (Pn), and maximum quantum yield of photosystem II (Fv/Fm). Furthermore, coordinated upregulation of both C₃ and C₄ pathway enzymes was observed under low-light stress, accompanied by enhanced antioxidant capacity and reduced photoxidative damage. Transcriptomic profiling further revealed CdGLK1-mediated activation of photosynthetic machinery components spanning light harvesting, electron transport, and carbon fixation modules. These findings establish CdGLK1 as a master integrator of photoprotection and metabolic adaptation under light-limiting conditions, providing both mechanistic insights and practical strategies for developing shade-resilient turfgrass cultivars. Full article

The mechanisms underlying leaf variegation in the ornamental Ilex × ‘Solar Flare’ remain poorly understood. To investigate this phenomenon, we conducted a comprehensive characterization of its variegated leaves. Compared to green sectors, yellow sectors exhibited severe chloroplast structural abnormalities, including swollen chloroplasts, damaged thylakoid membranes, and reduced chloroplast numbers. These yellow sectors also showed significantly lower chlorophyll and carotenoid levels, along with a depletion of key chlorophyll precursors—protoporphyrin IX (Proto IX), magnesium protoporphyrin IX (Mg-Proto IX), and protochlorophyllide (Pchlide). Photosynthetic efficiency was significantly impaired. Comparative transcriptome analysis identified 3510 differentially expressed genes (DEGs) between yellow and green sectors. Key disruptions in chlorophyll biosynthesis included upregulated CHLD expression and downregulated CHLH and CHLG expression, leading to impaired chlorophyll synthesis. Additionally, chlorophyll degradation was accelerated by PAO upregulation. Defective chloroplast development in yellow sectors was associated with the downregulation of GLK1, GLK2, and thylakoid membrane-related genes (PsbC, PsbO, PsbR, PsaD, and PsaH). These molecular alterations likely drive the variegated phenotype of I. × ‘Solar Flare’. These observations advance our understanding of the genetic and physiological mechanisms regulating leaf variegation in this cultivar. Full article

Chloroplast biogenesis and development are essential processes in plants, profoundly influencing their growth, survival, and productivity. However, the transcription factors controlling chloroplast development, especially in roots, are poorly characterized. Here, we demonstrate that the ectopic expression of the seed-specific transcription factor Plant Growth Regulator 37 (PGA37) promotes chloroplast development in roots, causing root-greening. Using a steroid-inducible gene expression system and RNA-Seq, we identified 97 potential PGA37 target genes. Notably, PGA37 directly activates the transcription factor GOLDEN2-LIKE (GLK2), which governs chloroplast biogenesis. An overexpression of GLK2 replicated the root-greening phenotype observed in PGA37-overexpressing plants, while GLK2 mutation significantly reduced chlorophyll content and suppressed root-greening in PGA37-overexpressing seedlings. Furthermore, PGA37 directly binds to the promoters of type-B response regulators ARR13 and ARR21, thereby activating the cytokinin signaling pathway. Mutations in these regulators partially diminished chlorophyll accumulation in PGA37-overexpressing seedlings, suggesting that PGA37-regulated chloroplast development is partially mediated by the cytokinin signaling through ARR13 and ARR21. Taken together, we propose that PGA37 orchestrates chloroplast development by coordinately regulating transcription factors from various families, including GLK2, ARR13, and ARR21, positioning it as a key regulator of chloroplast development. Full article

Background/Objectives: The GARP transcription factor superfamily is crucial for plant growth, development, and stress responses. This study systematically identified and analyzed the GARP family genes in Populus deltoides to explore their roles in plant development and abiotic stress responses. Methods: A total of 58 PdGARP genes were identified using bioinformatics tools. Their physicochemical properties, genomic locations, conserved motifs, gene structures, and phylogenetic relationships were analyzed. Expression patterns under phosphorus and nitrogen deficiency, as well as tissue-specific expression, were investigated using RT-qPCR. Transgenic RNAi lines were generated to validate the function of GLK genes in chlorophyll biosynthesis. Results: The 58 PdGARP genes were classified into five subfamilies based on their evolutionary relationships and protein sequence similarity. Segmental duplication was found to be the primary driver of the PdGARP family’s expansion. Cis-regulatory elements (CREs) related to light, hormones, and abiotic stresses were identified in the promoters of PdGARP genes. Differential expression patterns were observed for NIGT1/HRS1/HHO and PHR/PHL subfamily members under phosphorus and nitrogen deficiency, indicating their involvement in stress responses. KAN subfamily members exhibited tissue-specific expression, particularly in leaves. Structural analysis of the GLK subfamily revealed conserved α-helices, extended chains, and irregular coils. Transgenic RNAi lines targeting GLK genes showed significant reductions in chlorophyll and carotenoid content. Conclusions: This study provides a comprehensive analysis of the GARP transcription factor superfamily in P. deltoides, highlighting their potential roles in nutrient signaling and stress response pathways. The findings lay the foundation for further functional studies of PdGARP genes and their application in stress-resistant breeding of poplar. Full article

GOLDEN2-LIKE (GLK) transcription factors are crucial regulators of chloroplast development and stress responses in plants. In this study, we investigated the GLK gene family in Phoebe bournei (Hemsl.) Yen C. Yang, a near-threatened species important for forestry and wood utilization in China. We identified 61 PbGLK genes which were classified into seven subfamilies. Our analyses of their phylogenetic relationships, gene structures, and chromosomal distribution revealed diverse characteristics. Expression profiling under different tissues and abiotic stresses showed that PbGLK25 and PbGLK30 were particularly responsive to drought, heat, light, and shade stresses, with significant upregulation. These findings highlight the potential role of PbGLK genes in stress adaptation and provide insights for the genetic improvement of P. bournei. Full article

Background: Pepper (Capsicum annuum L.) is a widely cultivated vegetable crop worldwide, with its rich fruit colors providing unique visual traits and economic value. This study investigated the genetic basis of the immature green fruit color by constructing a F₂ segregating population derived from a cross between yellow fruit C20 and green fruit C62 parent lines. Methods: Bulked segregant analysis sequencing (BSA-seq) was performed to identify genomic regions associated with fruit color. Candidate genes were pinpointed through functional annotation and genetic variation analysis, supported by SNP markers, genotype analysis, and transcriptome profiling. Results: Two genomic regions associated with fruit color were identified on chromosomes 1 (14.55–20.85 Mb) and 10 (10.15–22.85 Mb), corresponding to previously reported loci pc1 and pc10.1. Two chlorophyll synthesis-related genes, CaAPRR2 and CaGLK2, were identified as candidate regulators of fruit color. Mutations in these genes include a premature stop codon in both CaGLK2 and CaAPRR2. The mutation of CaAPRR2 and CaGLK2 jointly regulate the yellow fruit trait in pepper, with CaGLK2 being the major gene and CaAPRR2 being the minor gene. Transcriptome analysis showed that the expression levels of the two genes increased during the green ripening stage of the parent fruits, with higher expression levels of CaGLK2. Conclusions: This study identifies CaGLK2 and CaAPRR2 as key regulators of immature green fruit color in pepper, with CaGLK2 playing a predominant role. These findings provide a theoretical foundation and data support for elucidating the molecular regulatory mechanisms of fruit color and advancing marker-assisted breeding in pepper. Full article

In plants, hexokinase (HXK) is a kind of bifunctional enzyme involved in sugar metabolism and sugar signal transduction that plays important roles in plant growth and development and stress response. Some HXK genes without a phosphorylation function have been found in Arabidopsis, tobacco, etc., but these genes have not been identified in tomato. Therefore, further genome-wide systematic identification and characterization is necessary for tomato HXK genes. In this study, six HXK genes were identified from the tomato genome distributed across six different chromosomes, named SlHXK1-6. Gene structure analysis showed that the SlHXK genes contain the same number of introns and exons. Gene duplication and collinearity analysis revealed two pairs of tandem repeats among SlHXKs, and a higher collinearity between tomatoes and potatoes were found. Response elements associated with phytohormones, abiotic stresses, and growth and development were identified in the promoter sequences of SlHXKs. Quantitative real-time PCR (qRT-PCR) results further indicated the potential role of SlHXKs in tomato development and stress responses. The expression levels of most SlHXKs were significantly induced by abiotic stress, hormone, and sugar solution treatments. In particular, the expression of SlHXK1 was significantly induced by various treatments. Functional complementation experiments were performed using HXK-deficient yeast strain YSH7.4-3C (hxk1, hxk2, and glk1), and the results showed that SlHXK5 and SlHXK6 were unable to phosphorylate glucose and fructose in yeast. In conclusion, these results provide valuable foundations for further exploring the sugar metabolism and sugar signal transduction mechanisms of HXK and the functions of SlHXK genes in various abiotic stresses, and some SlHXKs may be key genes for enhancing plants’ tolerance to abiotic stresses. Full article

Spiroplasma citri, a bacterium from the class Mollicutes, is the causative agent of citrus stubborn disease, a serious threat to Moroccan citrus crops, with yield losses reaching 45%. Despite its long-standing presence since 1949 and regulations mandating disease-free citrus plants, data on S. citri in Morocco remain scarce. This study investigates the pathogenicity and symptom variability of Moroccan S. citri isolates using biological indexing and genetic mapping based on the Spiralin and P58 genes. Biological indexing through reverse inoculation revealed that seven out of ten isolates caused moderate to intense symptoms within 8 to 10 weeks, with symptom severity varying across citrus cultivars and regions. These findings suggest variations in pathogen titer. Molecular analysis showed that Moroccan isolates (27GH, 3GH, 8GH, 56MK, 16MK, 60MK, 2GLK, 13SS, and 30S1) exhibited complete (100%) sequence similarity with each other and the reference strain R2-A8. Furthermore, these isolates displayed a high degree of similarity (99.75%) to a Corsican isolate (U13995) and a 94% similarity to an Iranian isolate (KP666137). Analysis of the P58 gene confirmed a high level of homogeneity with Moroccan reference strain R8-A2, closely aligning (99.75%) with the American BR3-3X strain, and 98% similarity to isolates from Syria and Iran. This study lays a foundational insight into the molecular characterization of S. citri in Morocco and provides a groundwork for future research into managing citrus stubborn disease. Full article

The Golden2-like (GLK) transcription factors belong to the GARP family of transcription factors and play significant roles in plant growth, development, and responses to both abiotic and biotic stresses. This study employed bioinformatics and expression analyses to investigate the regulatory roles of wheat GLK proteins under various stress conditions, including abscisic acid (ABA) treatment, osmotic stress, and infection by Fusarium graminearum. The study identified 125 TaGLK proteins and revealed that TaGLKs play a significant role in wheat’s development and response to adverse environmental conditions. The results indicate that TaGLKs may serve as potential transcriptional regulators capable of integrating multiple cellular signals to coordinate various developmental and physiological processes. Evolutionary analysis classified the TaGLK proteins into six subgroups, which shared similar conserved domains and motifs. Protein–protein interaction network analysis revealed that TaGLKs are involved in photoreceptor activity, cell cycle progression, and protein regulation. Gene expression analysis of TaGLKs discovered that they play key functions in wheat development, as well as regulation of biotic and abiotic stress conditions. RT-qPCR analysis showed that TaGLKs regulate earlier and late effects of osmotic stress, F. graminearum infections, and ABA treatment in wheat. These findings provide knowledge for future studies of the functions of TaGLK TFs in wheat stress tolerance and development, which could have significant implications for enhancing wheat tolerance to various environmental stressors. Full article

Cotton is a crucial economic crop that supplies natural fibers for the textile industry, with fiber quality being greatly impacted by abiotic stress throughout its growth stages. The Golden2-Like (GLK) gene family plays a key role in plant development and adaptation to abiotic stress. However, the specific functions and regulatory mechanisms of GLK members in cotton remain largely unexplored. In this study, a thorough analysis of GLK in four cotton species (Gossypium arboreum, G. raimondii, G. hirsutum, and G. barbadense) was conducted. A total of 198 GLK genes were identified in cotton. Conserved sequence analysis revealed that most GLK proteins contain two highly conserved domains: a MYB DNA-binding domain and a C-terminal (GCT) box. Promoter element analysis results show that the GLK gene family contains many stress response-related elements. Expression analysis demonstrated that GhGLK2, GhGLK11, GhGLK16, and GhGLK30 responded significantly to drought, salt, and temperature stresses. And GhGLK2, GhGLK13, GhGLK38, GhGLK42, and GhGLK46 responded significantly to cotton development. Yeast one-hybrid, yeast two-hybrid, and dual-luciferase assay results indicate that GhGLK2 interacts with GhGUN5, GhPIL6, GhNAC6, GhTPX2, and GhERF10. These findings suggest that these GhGLKs may play crucial roles in regulating the response to abiotic stress. Overall, this study provides a solid theoretical foundation for understanding the role of the GLK gene family in cotton’s response to abiotic stress. Full article

Genus Pseudomonas bacteria mainly consume glucose through the Entner–Doudoroff (ED) route due to a lack of a functional Embden–Meyerhof–Parnas (EMP) pathway. In the present study, a 6-phosphogluconate dehydratase (edd) operon in the ED route was well investigated to find its structural characteristics and roles in the regulation of glucose consumption and 2-ketogluconic acid (2KGA) metabolism in the industrial 2KGA-producer P. plecoglossicida JUIM01. The edd operon contained four structural genes of edd, glk, gltR, and gtrS, encoding 6-PG dehydratase Edd, glucokinase Glk, response regulatory factor GltR, and histidine kinase GtrS, respectively. A promoter region was observed in the 5′-upstream of the edd gene, with a transcriptional start site located 129 bp upstream of the edd gene and in a pseudo-palindromic sequence of 5′-TTGTN₇ACAA-3′ specifically binding to the transcription factor HexR. The knockout of the edd gene showed a remarkably negative effect on cell growth and re-growth using 2KGA as a substrate, beneficial to 2KGA production, with an increase of 8%. The deletion of glk had no significant effect on the cell growth or glucose metabolism, while showing an adverse impact on the 2KGA production, with a decrease of 5%. The outputs of the present study would provide a theoretical basis for 2KGA-producer improvement with metabolic engineering strategies and the development and optimization of P. plecoglossicida as the chassis cells. Full article

GOLDEN2-like (GLK) transcription factor genes are involved in chloroplast biogenesis during all stages of plant growth and development, as well as in the response to biotic and abiotic stresses. However, little is known about this transcription factor family in eggplant. In this study, we identified 54 GLK genes in the eggplant genome (S. melongena L.) and classified them into seven groups (G1–G7). Structural analysis illustrated that the SmGLK proteins of specific groups are relatively conserved. Cis-acting elements indicated that these genes are likely to be involved in multiple responses stimulated by light, phytohormones, and abiotic stress. Collinear analysis indicated that expansion of the SmGLK gene family primarily occurred through segmental duplication. Tissue-specific expression analysis revealed that SmGLKs were preferentially expressed in leaves, fruits, and seeds. Further screening of SmGLK genes revealed their differential expression under various treatments. Notably, SmGLK18 was significantly responsive to multiple phytohormones and stress treatments, whereas SmGLK3 and SmGLK12 were highly induced by ABA, IAA, SA, and drought treatments. Our study provides new information on the eggplant GLK family systematically and comprehensively. For the first time, we propose that SmGLK18 may play a key role in improving heat resistance. This study provides valuable candidate gene resources for further functional research and will benefit eggplant molecular breeding. Full article

Phalaenopsis orchids, with their unique appearance and extended flowering period, are among the most commercially valuable Orchidaceae worldwide. Particularly, the variegation in leaf color of Phalaenopsis significantly enhances the ornamental and economic value and knowledge of the molecular mechanism of leaf-color variegation in Phalaenopsis is lacking. In this study, an integrative analysis of the physiology, cytology, and transcriptome profiles was performed on Phalaenopsis Chia E Yenlin Variegata leaves between the green region (GR) and yellow region (YR) within the same leaf. The total chlorophyll and carotenoid contents in the YR exhibited a marked decrease of 72.18% and 90.21%, respectively, relative to the GR. Examination of the ultrastructure showed that the chloroplasts of the YR were fewer and smaller and exhibited indistinct stromal lamellae, ruptured thylakoids, and irregularly arranged plastoglobuli. The transcriptome sequencing between the GR and YR led to a total of 3793 differentially expressed genes, consisting of 1769 upregulated genes and 2024 downregulated genes. Among these, the chlorophyll-biosynthesis-related genes HEMA, CHLH, CRD, and CAO showed downregulation, while the chlorophyll-degradation-related gene SGR had an upregulated expression in the YR. Plant-hormone-related genes and transcription factors MYBs (37), NACs (21), ERFs (20), bHLH (13), and GLK (2), with a significant difference, were also analyzed. Furthermore, qRT-PCR experiments validated the above results. The present work establishes a genetic foundation for future studies of leaf-pigment mutations and may help to improve the economic and breeding values of Phalaenopsis. Full article

UV-B stress can affect plant growth at different levels, and although there is a multitude of evidence confirming the effects of UV-B radiation on plant photosynthesis, there are fewer studies using physiological assays in combination with multi-omics to investigate photosynthesis in alpine plants under stressful environments. Golden 2-like (G2-like/GLK) transcription factors (TFs) are highly conserved during evolution and may be associated with abiotic stress. In this paper, we used Handy-PEA and Imaging-PAM Maxi to detect chlorophyll fluorescence in leaves of Rhododendron chrysanthum Pall. (R. chrysanthum) after UV-B stress, and we also investigated the effect of abscisic acid (ABA) on photosynthesis in plants under stress environments. We used a combination of proteomics, widely targeted metabolomics, and transcriptomics to study the changes of photosynthesis-related substances after UV-B stress. The results showed that UV-B stress was able to impair the donor side of photosystem II (PSII), inhibit electron transfer and weaken photosynthesis, and abscisic acid was able to alleviate the damage caused by UV-B stress to the photosynthetic apparatus. Significant changes in G2-like transcription factors occurred in R. chrysanthum after UV-B stress, and differentially expressed genes localized in the Calvin cycle were strongly correlated with members of the G2-like TF family. Multi-omics assays and physiological measurements together revealed that G2-like TFs can influence photosynthesis in R. chrysanthum under UV-B stress by regulating the Calvin cycle. This paper provides insights into the study of photosynthesis in plants under stress, and is conducive to the adoption of measures to improve photosynthesis in plants under stress to increase yield. Full article

Chloroplasts is the site for photosynthesis, which is the main primary source of energy for plants. Golden2-like (GLK) is a key transcription factor that regulates chloroplast development and chlorophyll synthesis. However, most studies on GLK genes are performed in crops and model plants with less attention to woody plants. In this study, we identified the LhGLK1 and LhGLK2 genes in the woody plant Liriodendron hybrid, and they are specifically expressed in green tissues. We showed that overexpression of the LhGLK1 gene improves rosette leaf chlorophyll content and induces ectopic chlorophyll biogenesis in primary root and petal vascular tissue in Arabidopsis. Although these exhibit a late-flowering phenotype, transgenic lines accumulate more biomass in vegetative growth with improved photochemical quenching (qP) and efficiency of photosystem II. Taken together, we verified a conserved and ancient mechanism for regulating chloroplast biogenesis in Liriodendron hybrid and evaluated its effect on photosynthesis and rosette biomass accumulation in the model plant Arabidopsis. Full article