Meta QTL analysis for dissecting abiotic stress tolerance in chickpea.

BACKGROUND: Chickpea is prone to many abiotic stresses such as heat, drought, salinity, etc. which cause severe loss in yield. Tolerance towards these stresses is quantitative in nature and many studies have been done to map the loci influencing these traits in different populations using different markers. This study is an attempt to meta-analyse those reported loci projected over a high-density consensus map to provide a more accurate information on the regions influencing heat, drought, cold and salinity tolerance in chickpea. RESULTS: A meta-analysis of QTL reported to be responsible for tolerance to drought, heat, cold and salinity stress tolerance in chickpeas was done. A total of 1512 QTL responsible for the concerned abiotic stress tolerance were collected from literature, of which 1189 were projected on a chickpea consensus genetic map. The QTL meta-analysis predicted 59 MQTL spread over all 8 chromosomes, responsible for these 4 kinds of abiotic stress tolerance in chickpea. The physical locations of 23 MQTL were validated by various marker-trait associations and genome-wide association studies. Out of these reported MQTL, CaMQAST1.1, CaMQAST4.1, CaMQAST4.4, CaMQAST7.8, and CaMQAST8.2 were suggested to be useful for different breeding approaches as they were responsible for high per cent variance explained (PVE), had small intervals and encompassed a large number of originally reported QTL. Many putative candidate genes that might be responsible for directly or indirectly conferring abiotic stress tolerance were identified in the region covered by 4 major MQTL- CaMQAST1.1, CaMQAST4.4, CaMQAST7.7, and CaMQAST6.4, such as heat shock proteins, auxin and gibberellin response factors, etc. CONCLUSION: The results of this study should be useful for the breeders and researchers to develop new chickpea varieties which are tolerant to drought, heat, cold, and salinity stresses.

Overexpression of rice lectin receptor-like kinase, OsLec-RLK, confers salinity stress tolerance and increases seed yield in pigeon pea (Cajanus cajan (L.) Millsp.).

KEY MESSAGE: OsLec-RLK overexpression enhances cell signalling and salt stress tolerance in pigeon pea, enhancing seed yield and harvest index and thus, enabling marginal lands to increase food and nutritional security. Lectin Receptor-like kinases (Lec-RLKs) are highly effective cell signaling molecules that counteract various stresses, including salt stress. We engineered pigeon pea by overexpressing OsLec-RLK gene for enhancing salt tolerance. The OsLec-RLK overexpression lines demonstrated superior performance under salt stress, from vegetative to reproductive phase, compared to wild types (WT). The overexpression lines had significantly higher K+/Na+ ratio than WT exposed to 100 mM NaCl. Under salt stress, transgenic lines showed higher levels of chlorophyll, proline, total soluble sugars, relative water content, and peroxidase and catalase activity than WT plants. Membrane injury index and lipid peroxidation were significantly reduced in transgenic lines. Analysis of phenological and yield attributes confirmed that the OsLec-RLK pigeon pea lines maintain plant vigor, with 10.34-fold increase in seed yield (per plant) and 4-5-fold increase in harvest index of overexpression lines, compared to wild type. Meanwhile, the overexpression of OsLec-RLK up-regulated the expression levels of histone deacetylase1, acyl CoA, ascorbate peroxidase, peroxidase, glutathione reductase and catalase, which were involved in the K+/Na+ homeostasis pathway. This study showed the potential of OsLec-RLK gene for increasing crop productivity and yields under salt stress and enabling the crops to be grown on marginal lands for increasing food and nutritional security.

Overexpression of bacterial γ-glutamylcysteine synthetase increases toxic metal(loid)s tolerance and accumulation in Crambe abyssinica.

KEY MESSAGE: Transgenic Crambe abyssinica lines overexpressing γ-ECS significantly enhance tolerance to and accumulation of toxic metal(loid)s, improving phytoremediation potential and offering an effective solution for contaminated soil management. Phytoremediation is an attractive environmental-friendly technology to remove metal(loid)s from contaminated soils and water. However, tolerance to toxic metals in plants is a critical limiting factor. Transgenic Crambe abyssinica lines were developed that overexpress the bacterial γ-glutamylcysteine synthetase (γ-ECS) gene to increase the levels of non-protein thiol peptides such as γ-glutamylcysteine (γ-EC), glutathione (GSH), and phytochelatins (PCs) that mediate metal(loid)s detoxification. The present study investigated the effect of γ-ECS overexpression on the tolerance to and accumulation of toxic As, Cd, Pb, Hg, and Cr supplied individually or as a mixture of metals. Compared to wild-type plants, γ-ECS transgenics (γ-ECS1-8 and γ-ECS16-5) exhibited a significantly higher capacity to tolerate and accumulate these elements in aboveground tissues, i.e., 76-154% As, 200-254% Cd, 37-48% Hg, 26-69% Pb, and 39-46% Cr, when supplied individually. This is attributable to enhanced production of GSH (82-159% and 75-87%) and PC2 (27-33% and 37-65%) as compared to WT plants under AsV and Cd exposure, respectively. The levels of Cys and γ-EC were also increased by 56-67% and 450-794% in the overexpression lines compared to WT plants under non-stress conditions, respectively. This likely enhanced the metabolic pathway associated with GSH biosynthesis, leading to the ultimate synthesis of PCs, which detoxify toxic metal(loid)s through chelation. These findings demonstrate that γ-ECS overexpressing Crambe lines can be used for the enhanced phytoremediation of toxic metals and metalloids from contaminated soils.

Plasma membrane intrinsic protein OsPIP2;6 is involved in root-to-shoot arsenic translocation in rice (Oryza sativa L.).

KEY MESSAGE: This study demonstrates the crucial role of OsPIP2;6 for translocation of arsenic from roots to shoots, which can decrease arsenic accumulation in rice for improved food safety. Arsenic (As) contamination in food and water, primarily through rice consumption, poses a significant health risk due to its natural tendency to accumulate inorganic arsenic (iAs). Understanding As transport mechanisms is vital for producing As-free rice. This study investigates the role of rice plasma membrane intrinsic protein, OsPIP2;6, for AsIII tolerance and accumulation. RNAi-mediated suppression of OsPIP2;6 expression resulted in a substantial (35-65%) reduction in As accumulation in rice shoots, while root arsenic levels remained largely unaffected. Conversely, OsPIP2;6 overexpression led to 15-76% higher arsenic accumulation in shoots, with no significant change in root As content. In mature plants, RNAi suppression caused (19-26%) decrease in shoot As, with flag leaves and grains showing a 16% reduction. OsPIP2;6 expression was detected in both roots and shoots, with higher transcript levels in shoots. Localization studies revealed its presence in vascular tissues of both roots and shoots. Overall, our findings highlight OsPIP2;6's role in root-to-shoot As translocation, attributed to its specific localization in the vascular tissue of roots and leaves. This knowledge can facilitate the development of breeding programs to mitigate As accumulation in rice and other food crops for improved food safety and increasing productivity on As-contaminated soils.

Influence of nanoscale sulfur on mercury accumulation and plant growth in oilseed rape seedlings (Brassica napus L.) grown on mercury-contaminated soil.

Mercury (Hg) pollution has seriously threatened the crop productivity and food security. In the present research, experiments were conducted to assess the influence of nanoscale sulfur/sulfur nanoparticles and the corresponding bulk and ionic sulfur forms on the growth and Hg accumulation of oilseed rape seedlings grown on Hg-contaminated soil, as well as the transformation of soil Hg fractions. The results showed a significant reduction in fresh biomass for seedlings grown on 80-200 mg/kg Hg-polluted soil after 30 days. At 120 mg/kg Hg treatment, 100-300 mg/kg sulfur nanoparticles (SNPs) application counteracted Hg toxicity more effectively compared to the corresponding bulk sulfur particles (BSPs) and ionic sulfur (sulfate) treatments. The seedlings treated with 120 mg/kg Hg + 300 mg/kg SNPs gained 54.2 and 56.9% more shoot and root biomass, respectively, compared to those treated with Hg alone. Meanwhile, 300 mg/kg SNPs application decreased Hg accumulation by 18.9 and 76.5% in shoots and roots, respectively, relative to Hg alone treatment.SNPs treatment caused more Hg to be blocked in the soil and accumulating significantly less Hg in plants as compared to other S forms. The chemical fractions of Hg in the soil were subsequently investigated, and the solubility of Hg was significantly decreased by applying SNPs to the soil. Especially 200-300 mg/kg SNPs treatments caused the ratio of the soluble/exchangeable and the specifically absorbed fraction to be the lowest, accounting for 1.95-4.13% of the total Hg of soil. These findings suggest that adding SNPs to Hg-contaminated soils could be an effective measure for immobilizing soluble Hg and decreasing the Hg concentration in the edible parts of crops. The results of the current study hold promise for the practical application of SNPs to Hg-contaminated farmland for better yields and simultaneously increasing the food safety.

The novelty of this study is the selection of oilseed rape and nanoscale sulfur (NS) or sulfur nanoparticles (SNPs) as nontoxic nanomaterial to counteract the Hg toxicity and accumulation. Oilseed rape was selected due to its wide adaptability to various environmental conditions and the high-value oil for human consumption and biofuels production. These advantages make oilseed rape a highly valuable crop for various applications. NS was selected due to its reported ability to limit the uptake of heavy metals in oilseed rape, rice, and wheat along with other crops and subsequently restrict the toxicity of heavy metals in these plants and improve food safety. In this study, we evaluated the growth, Hg accumulation, and the resulting toxicity in oilseed rape grown on Hg-contaminated soil, with or without amendments with NS. The outcomes from this study provided evidence of the significant potential of NS in preventing Hg bioaccumulation and improving crop yields in oilseed rape. This provides opportunity to use NS as an ideal non-GMO approach to limit toxic metals in crops.

Effects of sulfur nanoparticles on rhizosphere microbial community changes in oilseed rape plantation soil under mercury stress.

In the present study, experiments were conducted to assess the influence of nanoscale sulfur in the microbial community structure of metallophytes in Hg-contaminated rhizosphere soil for planting rapeseed. The results showed that the richness and diversity of the rhizobacteria community decreased significantly under Hg stress, but increased slightly after SNPs addition, with a reduction in the loss of Hg-sensitive microorganisms. Moreover, all changes in the relative abundances of the top ten phyla influenced by Hg treatment were reverted when subjected to Hg + SNPs treatment, except for Myxococcota and Bacteroidota. Similarly, the top five genera, whose relative abundance decreased the most under Hg alone compared to CK, increased by 19.05%-54.66% under Hg + SNPs treatment compared with Hg alone. Furthermore, the relative abundance of Sphingomonas, as one of the dominant genera for both CK and Hg + SNPs treatment, was actively correlated with plant growth. Rhizobacteria, like Pedobacter and Massilia, were significantly decreased under Hg + SNPs and were positively linked to Hg accumulation in plants. This study suggested that SNPs could create a healthier soil microecological environment by reversing the effect of Hg on the relative abundance of microorganisms, thereby assisting microorganisms to remediate heavy metal-contaminated soil and reduce the stress of heavy metals on plants.

In this manuscript, we first comprehensively investigated the changes in the rhizosphere microbial community structure of metallophytes in Hg-contaminated soil with SNPs addition, as well as the relationship between soil microbiology and plant resistance to Hg stress. Our results demonstrated that SNPs exhibit a significant advantage in improving rhizosphere microecology by increasing the abundance of beneficial rhizobacteria, thereby alleviating heavy metal toxicity, and promoting plant growth. This study is the first study describing the response of soil microorganisms coexposed to heavy metals and SNPs, providing valuable information for the potential use of SNPs to assist phytoremediation of toxic metal pollution and its impact on soil microbial communities.

Comprehensive meta-QTL analysis for dissecting the genetic architecture of stripe rust resistance in bread wheat.

BACKGROUND: Yellow or stripe rust, caused by the fungus Puccinia striiformis f. sp. tritici (Pst) is an important disease of wheat that threatens wheat production. Since developing resistant cultivars offers a viable solution for disease management, it is essential to understand the genetic basis of stripe rust resistance. In recent years, meta-QTL analysis of identified QTLs has gained popularity as a way to dissect the genetic architecture underpinning quantitative traits, including disease resistance. RESULTS: Systematic meta-QTL analysis involving 505 QTLs from 101 linkage-based interval mapping studies was conducted for stripe rust resistance in wheat. For this purpose, publicly available high-quality genetic maps were used to create a consensus linkage map involving 138,574 markers. This map was used to project the QTLs and conduct meta-QTL analysis. A total of 67 important meta-QTLs (MQTLs) were identified which were refined to 29 high-confidence MQTLs. The confidence interval (CI) of MQTLs ranged from 0 to 11.68 cM with a mean of 1.97 cM. The mean physical CI of MQTLs was 24.01 Mb, ranging from 0.0749 to 216.23 Mb per MQTL. As many as 44 MQTLs colocalized with marker-trait associations or SNP peaks associated with stripe rust resistance in wheat. Some MQTLs also included the following major genes- Yr5, Yr7, Yr16, Yr26, Yr30, Yr43, Yr44, Yr64, YrCH52, and YrH52. Candidate gene mining in high-confidence MQTLs identified 1,562 gene models. Examining these gene models for differential expressions yielded 123 differentially expressed genes, including the 59 most promising CGs. We also studied how these genes were expressed in wheat tissues at different phases of development. CONCLUSION: The most promising MQTLs identified in this study may facilitate marker-assisted breeding for stripe rust resistance in wheat. Information on markers flanking the MQTLs can be utilized in genomic selection models to increase the prediction accuracy for stripe rust resistance. The candidate genes identified can also be utilized for enhancing the wheat resistance against stripe rust after in vivo confirmation/validation using one or more of the following methods: gene cloning, reverse genetic methods, and omics approaches.

Seed priming can enhance and retain stress tolerance in ensuing generations by inducing epigenetic changes and trans-generational memory.

The significance of priming in enhancing abiotic stress tolerance is well-established in several important crops. Priming positively impacts plant growth and improves stress tolerance at multiple developmental stages, and seed priming is one of the most used methods. Seed priming influences the pre-germinative metabolism that ensures proper germination, early seedling establishment, enhanced stress tolerance and yield, even under unfavourable environmental conditions. Seed priming involves pre-exposure of seeds to mild stress, and this pre-treatment induces specific changes at the physiological and molecular levels. Interestingly, priming can improve the efficiency of the DNA repair mechanism, along with activation of specific signalling proteins and transcription factors for rapid and efficient stress tolerance. Notably, such acquired stress tolerance may be retained for longer duration, namely, later developmental stages or even subsequent generations. Epigenetic and chromatin-based mechanisms such as DNA methylation, histone modifications, and nucleosome positioning are some of the key molecular changes involved in priming/stress memory. Further, the retention of induced epigenetic changes may influence the priming-induced trans-generational stress memory. This review discusses known and plausible seed priming-induced molecular mechanisms that govern germination and stress memory within and across generations, highlighting their role in regulating the plant response to abiotic stresses. Understanding the molecular mechanism for activation of stress-responsive genes and the epigenetic changes resulting from seed priming will help to improve the resiliency of the crops for enhanced productivity under extreme environments.

Overexpression of gamma-glutamyl cyclotransferase 2;1 (CsGGCT2;1) reduces arsenic toxicity and accumulation in Camelina sativa (L.).

KEY MESSAGE: Overexpressing CsGGCT2;1 in Camelina enhances arsenic tolerance, reducing arsenic accumulation by 40-60%. Genetically modified Camelina can potentially thrive on contaminated lands and help safeguard food quality and sustainable food and biofuel production. Environmental arsenic contamination is a serious global issue that adversely affects human health and diminishes the quality of harvested produce. Glutathione (GSH) is known to bind and detoxify arsenic and other toxic metals. A steady level of GSH is maintained within cells via the γ-glutamyl cycle. The γ-glutamyl cyclotransferases (GGCTs) have previously been shown to be involved in GSH degradation and increased tolerance to toxic metals in plants. In this study, we characterized the GGCT2;1 homolog from Camelina sativa for its role in arsenic tolerance and accumulation. Overexpression of CsGGCT2;1 in Camelina under CaMV35S constitutive promoter resulted in strong tolerance to arsenite (AsIII). The overexpression (OE) lines had 2.6-3.5-fold higher shoots and sevenfold to tenfold enhanced root biomass on media supplemented with AsIII, relative to wild-type plants. The CsGGCT2;1 OE lines accumulated 40-60% less arsenic in root and shoot tissues compared to wild-type plants. Further, the OE lines had ~ twofold higher chlorophyll content and 35% lesser levels of malondialdehyde (MDA), an indicator of membrane damage via lipid peroxidation. There was a slight but non-significant increase in 5-oxoproline (5-OP), a product of GSH degradation, in OE lines. However, the transcript levels of Oxoprolinase 1 (OXP1) were upregulated, indicating the accelerated conversion of 5-OP to glutamate, which is further utilized for the resynthesis of GSH to maintain GSH homeostasis. Overall, this research suggests that genetically modified Camelina may have the potential for cultivation on contaminated marginal lands to reduce As accumulation; thereby could help in addressing food safety issues as well as future food and biofuel needs.

Heavy metal (loid)s phytotoxicity in crops and its mitigation through seed priming technology.

Unexpected bioaccumulation and biomagnification of heavy metal(loid)s (HMs) in the environment have become a predicament for all living organisms, including plants. The presence of these HMs in the plant system raised the level of reactive oxygen species (ROS) and remodeled several vital cellular biomolecules. These lead to several morphological, physiological, metabolic, and molecular aberrations in plants ranging from chlorosis of leaves to the lipid peroxidation of membranes, and degradation of proteins and nucleic acid including the modulation of the enzymatic system, which ultimately affects the plant growth and productivity. Plants are equipped with several mechanisms to counteract the HMs toxicity. Among them, seed priming (SP) technology has been widely tested with the use of several inorganic chemicals, plant growth regulators (PGRs), gasotransmitters, nanoparticles, living organisms, and plant leaf extracts. The use of these compounds has the potential to alleviate the HMs toxicity through the strengthening of the antioxidant defense system, generation of low molecular weight metallothionein's (MTs), and phytochelatins (PCs), and improving seedling vigor during early growth stages. This review presents an account of the sources, uptake and transport, and phytotoxic effects of HMs with special attention to different mechanism/s, occurring to mitigate the HMs toxicity in plants employing SP technology.Novelty statement: To the best of our knowledge, this review has delineated the consequences of HMs on the crucial plant processes, which ultimately affect plant growth and development. This review also compiled the up to dated information on phytotoxicity of HMs through the use of SP technology, this review discussed how different types of SP approaches help in diminishing the concentration HMs in plant systems. Also, we depicted mechanisms, represent how HMs transport and their actions on cellular levels, and emphasized, how diverse SP technology effectiveness in the mitigation of plants' phytotoxicity in unique ways.

Co-exposure of sulfur nanoparticles and Cu alleviate Cu stress and toxicity to oilseed rape Brassica napus L.

Experiments were performed to explore the impact of sulfur nanoparticles (SNPs) on growth, Cu accumulation, and physiological and biochemical responses of oilseed rape (Brassica napus L.) inoculated with 5 mg/L Cu-amended MS medium supplemented with or without 300 mg/L SNPs exposure. Cu exerted severe phytotoxicity and inhibited plant growth. SNPs application enhanced the shoot height, root length, and dry weight of shoot and root by 34.6%, 282%, 41.7% and 37.1%, respectively, over Cu treatment alone, while the shoot and root Cu contents and Cu-induced lipid perodixation as the malondialdehyde (MDA) levels in shoots and roots were decreased by 37.6%, 35%, 28.4% and 26.8%. Further, the increases in superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), ascorbate peroxidase (APX), glutathione reductase (GR) and glutathione S-transferase (GST) enzyme activities caused by Cu stress were mitigated in shoots (10.9%-37.1%) and roots (14.6%-35.3%) with SNPs addition. SNPs also positively counteracted the negative effects on shoot K, Ca, P, Mg, Mn, Zn and Fe contents and root K, Ca, Mg and Mn contents from Cu exposure alone, and significantly promoted the nutrients accumulation in plant. Additionally, in comparison with common bulk sulfur particles (BSPs) and sulfate, SNPs showed more positive effects on promoting growth in shoots (6.7% and 19.5%) and roots (10.9% and 15.1%), as well as lowering the shoot Cu content (40.1% and 43.3%) under Cu stress. Thus, SNPs application has potential to be a green and sustainable technology for increasing plant productivity and reducing accumulation of toxic metals in heavy metal polluted soils.

Development and characterization of nitrogen and phosphorus use efficiency responsive genic and miRNA derived SSR markers in wheat.

Among all the nutrients, nitrogen (N) and phosphorous (P) are the most limiting factors reducing wheat production and productivity world-wide. These macronutrients are directly applied to soil in the form of fertilizers. However, only 30-40% of these applied fertilizers are utilized by crop plants, while the rest is lost through volatilization, leaching, and surface run off. Therefore, to overcome the deficiency of N and P, it becomes necessary to improve their use efficiency. Marker-assisted selection (MAS) combined with traditional plant breeding approaches is considered best to improve the N and P use efficiency (N/PUE) of wheat varieties. In this study, we developed and evaluated a total of 98 simple sequence repeat (SSR) markers including 66 microRNAs and 32 gene-specific SSRs on a panel of 10 (N and P efficient/deficient) wheat genotypes. Out of these, 35 SSRs were found polymorphic and have been used for the study of genetic diversity and population differentiation. A set of two SSRs, namely miR171a and miR167a were found candidate markers able to discriminate contrasting genotypes for N/PUE, respectively. Therefore, these two markers could be used as functional markers for characterization of wheat germplasm for N and P use efficiency. Target genes of these miRNAs were found to be highly associated with biological processes (24 GO terms) as compared to molecular function and cellular component and shows differential expression under various P starving conditions and abiotic stresses.

ASRmiRNA: Abiotic Stress-Responsive miRNA Prediction in Plants by Using Machine Learning Algorithms with Pseudo K-Tuple Nucleotide Compositional Features.

MicroRNAs (miRNAs) play a significant role in plant response to different abiotic stresses. Thus, identification of abiotic stress-responsive miRNAs holds immense importance in crop breeding programmes to develop cultivars resistant to abiotic stresses. In this study, we developed a machine learning-based computational method for prediction of miRNAs associated with abiotic stresses. Three types of datasets were used for prediction, i.e., miRNA, Pre-miRNA, and Pre-miRNA + miRNA. The pseudo K-tuple nucleotide compositional features were generated for each sequence to transform the sequence data into numeric feature vectors. Support vector machine (SVM) was employed for prediction. The area under receiver operating characteristics curve (auROC) of 70.21, 69.71, 77.94 and area under precision-recall curve (auPRC) of 69.96, 65.64, 77.32 percentages were obtained for miRNA, Pre-miRNA, and Pre-miRNA + miRNA datasets, respectively. Overall prediction accuracies for the independent test set were 62.33, 64.85, 69.21 percentages, respectively, for the three datasets. The SVM also achieved higher accuracy than other learning methods such as random forest, extreme gradient boosting, and adaptive boosting. To implement our method with ease, an online prediction server "ASRmiRNA" has been developed. The proposed approach is believed to supplement the existing effort for identification of abiotic stress-responsive miRNAs and Pre-miRNAs.

Physiological and molecular signatures reveal differential response of rice genotypes to drought and drought combination with heat and salinity stress.

Rice is the staple food for more than 3.5 billion people worldwide. The sensitivity of rice to heat, drought, and salinity is well documented. However, rice response to combinations of these stresses is not well understood. A contrasting set of rice genotypes for heat (N22, Gharib), drought (Moroberekan, Pusa 1121) and salinity (Pokkali, IR64) were selected to characterize their response under drought, and combination of drought with heat and salinity at the sensitive seedling stage. Sensitive genotypes (IR64, Pusa 1121, Gharib) recorded higher reactive oxygen species accumulation (20-40%), membrane damage (8-65%) and reduction in photosynthetic efficiency (10-23%) across the stress and stress combinations as compared to stress tolerant checks. On the contrary, N22 and Pokkali performed best under drought + heat, and drought + salinity combination, respectively. Moreover, gene expression pattern revealed the highest expression of catalase (CAT), ascorbate peroxidase (APX) and GATA28a in N22 under heat + drought, whereas the highest expression of CAT, APX, superoxide dismutase (SOD), DEHYDRIN, GATA28a and GATA28b in Pokkali under drought + salinity. Interestingly, the phenotypic variation and expression level of genes highlighted the role of different set of physiological traits and genes under drought and drought combination with heat and salinity stress. This study reveals that rice response to stress combinations was unique with rapid readjustment at physiological and molecular levels. Moreover, phenotypic changes under stress combinations showed substantial adaptive plasticity in rice, which warrant further investigations at molecular level. Supplementary Information: The online version contains supplementary material available at 10.1007/s12298-022-01162-y.

Nanoscale Sulfur Improves Plant Growth and Reduces Arsenic Toxicity and Accumulation in Rice (Oryza sativa L.).

Rice is known to accumulate arsenic (As) in its grains, posing serious health concerns for billions of people globally. We studied the effect of nanoscale sulfur (NS) on rice seedlings and mature plants under As stress. NS application caused a 40% increase in seedling biomass and a 26% increase in seed yield of mature plants compared to untreated control plants. AsIII exposure caused severe toxicity to rice; however, coexposure of plants to AsIII and NS alleviated As toxicity, and growth was significantly improved. Rice seedlings treated with AsIII + NS produced 159 and 248% more shoot and root biomass, respectively, compared to plants exposed to AsIII alone. Further, AsIII + NS-treated seedlings accumulated 32 and 11% less As in root and shoot tissues, respectively, than the AsIII-alone treatment. Mature plants treated with AsIII + NS produced 76, 110, and 108% more dry shoot biomass, seed number, and seed yield, respectively, and accumulated 69, 38, 18, and 54% less total As in the root, shoot, flag leaves, and grains, respectively, compared to AsIII-alone-treated plants. A similar trend was observed in seedlings treated with AsV and NS. The ability of sulfur (S) to alleviate As toxicity and accumulation is clearly size dependent as NS could effectively reduce bioavailability and accumulation of As in rice via modulating the gene expression activity of As transport, S assimilatory, and glutathione synthesis pathways to facilitate AsIII detoxification. These results have significant environmental implications as NS application in agriculture has the potential to decrease As in the food chain and simultaneously enable crops to grow and produce higher yields on marginal and contaminated lands.

Elucidating the Response of Crop Plants towards Individual, Combined and Sequentially Occurring Abiotic Stresses.

In nature, plants are exposed to an ever-changing environment with increasing frequencies of multiple abiotic stresses. These abiotic stresses act either in combination or sequentially, thereby driving vegetation dynamics and limiting plant growth and productivity worldwide. Plants' responses against these combined and sequential stresses clearly differ from that triggered by an individual stress. Until now, experimental studies were mainly focused on plant responses to individual stress, but have overlooked the complex stress response generated in plants against combined or sequential abiotic stresses, as well as their interaction with each other. However, recent studies have demonstrated that the combined and sequential abiotic stresses overlap with respect to the central nodes of their interacting signaling pathways, and their impact cannot be modelled by swimming in an individual extreme event. Taken together, deciphering the regulatory networks operative between various abiotic stresses in agronomically important crops will contribute towards designing strategies for the development of plants with tolerance to multiple stress combinations. This review provides a brief overview of the recent developments in the interactive effects of combined and sequentially occurring stresses on crop plants. We believe that this study may improve our understanding of the molecular and physiological mechanisms in untangling the combined stress tolerance in plants, and may also provide a promising venue for agronomists, physiologists, as well as molecular biologists.

Increased Cuticle Waxes by Overexpression of WSD1 Improves Osmotic Stress Tolerance in Arabidopsis thaliana and Camelina sativa.

To ensure global food security under the changing climate, there is a strong need for developing 'climate resilient crops' that can thrive and produce better yields under extreme environmental conditions such as drought, salinity, and high temperature. To enhance plant productivity under the adverse conditions, we constitutively overexpressed a bifunctional wax synthase/acyl-CoA:diacylglycerol acyltransferase (WSD1) gene, which plays a critical role in wax ester synthesis in Arabidopsis stem and leaf tissues. The qRT-PCR analysis showed a strong upregulation of WSD1 transcripts by mannitol, NaCl, and abscisic acid (ABA) treatments, particularly in Arabidopsis thaliana shoots. Gas chromatography and electron microscopy analyses of Arabidopsis seedlings overexpressing WSD1 showed higher deposition of epicuticular wax crystals and increased leaf and stem wax loading in WSD1 transgenics compared to wildtype (WT) plants. WSD1 transgenics exhibited enhanced tolerance to ABA, mannitol, drought and salinity, which suggested new physiological roles for WSD1 in stress response aside from its wax synthase activity. Transgenic plants were able to recover from drought and salinity better than the WT plants. Furthermore, transgenics showed reduced cuticular transpirational rates and cuticle permeability, as well as less chlorophyll leaching than the WT. The knowledge from Arabidopsis was translated to the oilseed crop Camelina sativa (L.) Crantz. Similar to Arabidopsis, transgenic Camelina lines overexpressing WSD1 also showed enhanced tolerance to drought stress. Our results clearly show that the manipulation of cuticular waxes will be advantageous for enhancing plant productivity under a changing climate.

Nanotechnology as a new sustainable approach for controlling crop diseases and increasing agricultural production.

Climate change will negatively affect crop production by exacerbating the incidence of disease and decreasing the efficacy of conventional approaches to disease control. Nanotechnology is a promising new strategy for plant disease management that has many advantages over conventional products and approaches, such as better efficacy, reduced input requirements, and lower eco-toxicity. Studies on crop plants using various nanomaterials (NMs) as protective agents have produced promising results. This review focuses on the use of NMs in disease management through three different mechanisms: (i) as antimicrobial agents; (ii) as biostimulants that induce plant innate immunity; and (iii) as carriers for active ingredients such as pesticides, micronutrients, and elicitors. The potential benefits of nanotechnology are considered, together with the role that NMs might play in future disease management and crop adaptation measures.

Plant growth-regulating molecules as thermoprotectants: functional relevance and prospects for improving heat tolerance in food crops.

Among various abiotic stresses, heat stress is one of the most damaging, threatening plant productivity and survival all over the world. Warmer temperatures due to climatic anomalies above optimum growing temperatures have detrimental impacts on crop yield potential as well as plant distribution patterns. Heat stress affects overall plant metabolism in terms of physiology, biochemistry, and gene expression. Membrane damage, protein degradation, enzyme inactivation, and the accumulation of reactive oxygen species are some of the harmful effects of heat stress that cause injury to various cellular compartments. Although plants are equipped with various defense strategies to counteract these adversities, their defensive means are not sufficient to defend against the ever-rising temperatures. Hence, substantial yield losses have been observed in all crop species under heat stress. Here, we describe the involvement of various plant growth-regulators (PGRs) (hormones, polyamines, osmoprotectants, antioxidants, and other signaling molecules) in thermotolerance, through diverse cellular mechanisms that protect cells under heat stress. Several studies involving the exogenous application of PGRs to heat-stressed plants have demonstrated their role in imparting tolerance, suggesting the strong potential of these molecules in improving the performance of food crops grown under high temperature.

Engineering abiotic stress tolerance via CRISPR/ Cas-mediated genome editing.

Abiotic stresses, including drought, salinity, temperature, and heavy metals, pose a major challenge for crop production and cause substantial yield reduction worldwide. Breeding tolerant cultivars against these abiotic stresses is the most sustainable and eco-friendly approach to cope with this challenge. Advances in genome editing technologies provide new opportunities for crop improvement by employing precision genome engineering for targeted crop traits. However, the selection of the candidate genes is critical for the success of achieving the desired traits. Broadly speaking, these genes could fall into two major categories, structural and regulatory genes. Structural genes encode proteins that provide stress tolerance directly, whereas regulatory genes act indirectly by controlling the expression of other genes involved in different cellular processes. Additionally, cis-regulatory sequences are also vital for achieving stress tolerance. We propose targeting of these regulatory and/or structural genes along with the cis-regulatory sequences via the clustered regularly interspaced short palindromic repeat (CRISPR)/CRISPR-associated protein 9 (Cas9) system as a robust, efficient, and practical approach for developing crop varieties resilient to climate change. We also discuss the possibility of creating novel quantitative trait loci for abiotic stress tolerance via the CRISPR/Cas-mediated targeting of promoters. It is hoped that these genome editing tools will not only make a significant contribution towards raising novel plant types having tolerance to multiple abiotic stresses but will also aid in public acceptance of these products in years to come. This article is an attempt to critically evaluate the suitability of available tools and the target genes for obtaining plants with improved tolerance to abiotic stresses.