Stresses, Volume 2, Issue 3 (September 2022) – 8 articles

Cadmium (Cd) is an environmental toxicant of public health significance worldwide. Diet is the main Cd exposure source in the non-occupationally exposed and non-smoking populations. Metal transporters for iron (Fe), zinc (Zn), calcium (Ca), and manganese (Mn) are involved in the assimilation and distribution of Cd to cells throughout the body. Due to an extremely slow elimination rate, most Cd is retained by cells, where it exerts toxicity through its interaction with sulfur-containing ligands, notably the thiol (-SH) functional group of cysteine, glutathione, and many Zn-dependent enzymes and transcription factors. The simultaneous induction of heme oxygenase-1 and the metal-binding protein metallothionein by Cd adversely affected the cellular redox state and caused the dysregulation of Fe, Zn, and copper. Experimental data indicate that Cd causes mitochondrial dysfunction via disrupting the metal homeostasis of this organelle. The present review focuses on the adverse metabolic outcomes of chronic exposure to low-dose Cd. Current epidemiologic data indicate that chronic exposure to Cd raises the risk of type 2 diabetes by several mechanisms, such as increased oxidative stress, inflammation, adipose tissue dysfunction, increased insulin resistance, and dysregulated cellular intermediary metabolism. The cellular stress response mechanisms involving the catabolism of heme, mediated by heme oxygenase-1 and -2 (HO-1 and HO-2), may mitigate the cytotoxicity of Cd. The products of their physiologic heme degradation, bilirubin and carbon monoxide, have antioxidative, anti-inflammatory, and anti-apoptotic properties. Full article

Trehalose 6-phosphate (T6P) regulates sugar levels and starch metabolism in a plant cell and thus interacts with various signaling pathways, and after converting T6P into trehalose (Tre), it acts as a vital osmoprotectant under stress conditions. This study was conducted using wheat (Triticum aestivum L. cv. Norin 61) and mustard (Brassica juncea L. cv. BARI sharisha 13) seedlings to investigate the role of Tre and T6P in improving salt and water deficit stress tolerance. The seedlings were grown hydroponically using Hyponex solution and exposed to salt (300 and 200 mM NaCl for wheat and mustard, respectively) and water deficit (20 and 12% PEG 6000 for wheat and mustard, respectively) stresses with or without Tre and T6P. The study demonstrated that salt and water deficit stress negatively influenced plant growth by destroying photosynthetic pigments and increasing oxidative damage. In response to salt and water deficit stresses, the generation of H₂O₂ increased by 114 and 67%, respectively, in wheat seedlings, while in mustard, it increased by 86 and 50%, respectively. Antioxidant defense systems were also altered by salt and water deficit stresses due to higher oxidative damage. The AsA content was reduced by 65 and 38% in wheat and 61 and 45% in mustard under salt and water deficit stresses, respectively. The subsequent negative results of salinity and water deficit can be overcome by exogenous application of Tre and T6P; these agents reduced the oxidative stress by decreasing H₂O₂ and TBARS levels and increasing enzymatic and non-enzymatic antioxidants. Moreover, the application of Tre and T6P decreased the accumulation of Na in the shoots and roots of wheat and mustard seedlings. Therefore, the results suggest that the use of Tre and T6P is apromising strategy to alleviate osmotic and ionic toxicity in plants under salt and water deficit stresses. Full article

Drought is amongst the most important stressors affecting maize production globally. Existing strategies to offset drought impacts are centered around the rapid development of drought-tolerant cultivars through plant breeding. However, under both current conditions and projected climate changes, additional stressors such as insect pests will co-occur. To determine the impact of combined insect and drought stress on drought tolerance in maize, we assessed the effects of Dalbulus maidis, drought, and both stresses combined in drought-tolerant maize hybrids. We measured several maize morphological growth traits (i.e., plant height, stem diameter, shoot weight, root weight, root length, and root-to-shoot ratio) at the end of a 28-day period of pulse-stress and no-stress control exposure. We found that seedling growth declined when both stressors co-occurred. Nevertheless, drought-tolerant maize hybrids remained strongly tolerant to drought regardless of D. maidis infestation. While our results showed that drought tolerance is maintained in drought-tolerant maize seedlings, future studies should address any effects on maize yield. Our study highlights the importance of testing the combined effects of drought and insect stressors to better predict insect–plant interactions in the context of plant breeding for drought-tolerant traits in a changing climate. Full article

The microalga Phaeodactylum tricornutum is considered a model diatom. It is the second diatom whose genome was sequenced and the first one genetically engineered. This permits its use as a cell factory for the production of high-value compounds for nutraceutical, cosmeceutical, pharmaceutical, biodiesel, and bioplastic applications. This study is focused on analyzing expression levels of enzymes involved in the synthesis of sulfoglycolipids and monogalactosyldiacylglycerols, compounds known to have anticancer and immunomodulatory activities, and genes coding antioxidant, heat shock and stress-responsive proteins, in various culturing conditions. Our data showed that both nutrient starvation and senescence induced the down-regulation of both sulfoglycolipid and monogalactosyldiacylglycerol synthesis-related genes and stress-responsive genes (compared to the replete condition), suggesting that the control condition, consisting of cells in the exponential phase in replete medium, is the condition with the highest expression of the genes of interest and worth of further bioactivity screening and chemical analyses for drug discovery and biotechnological applications. Full article

The halophytic crop Chenopodium quinoa has a remarkable resistance to harsh growth conditions in suboptimal environments and marginal soils. Additionally, quinoa is a pseudocereal and produces seeds with outstanding nutritional value. Quinoa is an allotetraploid (2n = 4× = 36) with an estimated genome size of approximately 1.5 Gbp. In plants, the family of pyrabactin resistance 1 (PYR1)/PYR1-like (PYL)/regulatory components of ABA receptors (RCAR) play a vital role in the initial step of ABA signaling, leading to abiotic stress resistance. Here 20 CqPYL genes were identified using the genome-search method. Based on the phylogenetic analysis, these CqPYL genes were divided into three classes or subfamilies. These genes have different structures and intron numbers, even within the same subfamily. Analysis of conserved motifs showed the presence of the PYR_PYL_RCAR motif domain in each PYL protein sequence. Furthermore, the tissue-specific expression of CqPYLs was analyzed through public available RNA-seq data. CqPYL4a/b and CqPYL8c/d showed higher expression levels in seedlings. Finally, 3D structures of the CqPYL proteins were predicted by homology modeling and analyzed through topology inspection to speculate on putative new ABA receptor features. This study provides a theoretical basis for further functional study of PYL genes for stress-resistance breeding of quinoa and other crops. Full article

Soil salinity has emerged as a serious issue for food security due to global climate change. It is estimated that currently about 62 million hectares or 20 percent of the world’s irrigated land is affected by salinity. Salinity is a serious problem in the coastal areas of Bangladesh. Isolation of salt-tolerant plant growth-promoting bacteria (PGPB) and applying them as bioinoculants in crop plants are considered promising and effective biotechnological approaches to combat soil salinity. This study aimed to screen salt-tolerant PGPB from the root, leaf, and rhizospheric soils of rice plants collected from salt-affected coastal areas including Chattogram, Noakhali, Lakshmipur, and Cox’s Bazar districts of Bangladesh and evaluated their performances on the seedling growth of rice. Out of forty-one salinity-tolerant bacterial isolates screened, Brevibacterium sediminis showed salinity tolerance up to 12% NaCl (w/v). In vitro bioassay revealed that B. sediminis promoted the seedling growth of rice cv. BRRI dhan29 (salinity susceptible) and BINAdhan-10 (salinity tolerant), and the growth-promoting effects were higher in BINAdhan-10. This study for the first time identified B. sediminis strain IBGE3C as a salt-tolerant PGPB from a widely cultivated rice variety, BRRI dhan28 in the Lakshmipur district of Bangladesh. Our results suggest that salt-tolerant PGPB isolated from the root, leaf, and rhizospheric soil of rice plants could be used as a low cost and environmentally friendly option for overcoming the detrimental effects of salt stress on rice plants in the southern coastal regions of Bangladesh. However, further studies are needed for assessing the efficacy of B. sediminis on enhancement of salinity tolerance, and growth and yield of rice under salinity stressed conditions. Full article

Hydrogen peroxide (H₂O₂) is a compound involved in some mammalian reactions and processes. It modulates and signals the redox metabolism of cells by acting as a messenger together with hydrogen sulfide (H₂S) and the nitric oxide radical (^•NO), activating specific oxidations that determine the metabolic response. The reaction triggered determines cell survival or apoptosis, depending on which downstream metabolic pathways are activated. There are several ways to produce H₂O₂ in cells, and cellular systems tightly control its concentration. At the cellular level, the accumulation of hydrogen peroxide can trigger inflammation and even apoptosis, and when its concentration in the blood reaches toxic levels, it can lead to bioenergetic failure. This review summarizes existing research from a chemical perspective on the role of H₂O₂ in various enzymatic pathways and how this biochemistry leads to physiological or pathological responses. Full article

The natural environment of crops is exposed to a complex collection of biotic and abiotic pressures. Abiotic stresses cover a diversity of environmental elements that cannot be avoided, such as temperature, drought, salinity, cold, heat, light, and water stress. Biotic stress is caused by living organisms with which plants coexist and interact. Pathogens and herbivores are examples of biotic stressors that can threaten food security and result in significant economic losses. Agricultural production systems differ in the extent of stress towards cultivated crops; agroforestry is considered to provide a protective function against environmental stress. The concept of this review was to assess the impact of environmental change and the atmospheric variability on the plants in agroforestry systems. The application of trees in field crop production has become more and more involved in practice, especially in areas with an extreme climate and unfavorable soil conditions. The main reasons for the rising interest are the effects of climate change, soil degradation, and erosion. Most of the trees are used as hedgerows or farm boundaries, or as scattered planting on the farm to control soil erosion as well as to improve farm productivity, which requires a thorough understanding of each stress element. Full article