Root-omics for drought tolerance in cool-season grain legumes

Molecular mechanism of drought resistance in soybean roots revealed using physiological and multi-omics analyses

Soybeans are one of the most cultivated crops worldwide and drought can seriously affect their growth and development. Many studies have elucidated the mechanisms through which soybean leaves respond to drought; however, little is known about these mechanisms in roots. We used two soybean varieties with different drought tolerances to study the morphological, physiological, and molecular response mechanisms of the root system to drought stress in seedlings. We found that drought stress led to a significant decrease in the root traits and an increase in antioxidant enzyme activity in the two varieties. Drought-resistant varieties accumulate large amounts of flavonoids and phenolic acids at the metabolic level, which causes variations in drought resistance. Additionally, differences in gene expression and drought-resistance pathways between the two varieties were clarified using transcriptome analysis. Through a multi-omics joint analysis, phenylpropanoid and isoflavonoid biosynthesis were identified as the core drought resistance pathways in soybean roots. Candidate genes and marker metabolites affecting drought resistance were identified. The phenylpropanoid pathway confers drought tolerance to roots by maintaining a high level of POD activity and mediates the biosynthesis of various secondary drought-resistant metabolites to resist drought stress. This study provides useful data for investigating plant root drought responses and offers theoretical support for plant breeding for drought resistance.

Cell dehydration of intergeneric hybrid induces subgenome-related specific responses

The aim was to identify subgenome-related specific responses in two types of triticale, that is, of the wheat-dominated genome (WDG) and rye-dominated genome (RDG), to water stress induced in the early phase (tillering) of plant growth. Higher activity of the primary metabolism of carbohydrates is a feature of the WDG type, while the dominance of the rye genome is associated with a higher activity of the secondary metabolism of phenolic compounds in the RDG type. The study analyzed carbohydrates and key enzymes of their synthesis, free phenolic compounds and carbohydrate-related components of the cell wall, monolignols, and shikimic acid (ShA), which is a key link between the primary and secondary metabolism of phenolic compounds. Under water stress, dominance of the wheat genome in the WDG type was manifested by an increased accumulation of the large subunit of Rubisco and sucrose phosphate synthase and a higher content of raffinose and stachyose compared with the RDG type. In dehydrated RDG plants, higher activity of L-phenylalanine ammonia lyase (PAL) and L-tyrosine ammonia lyase (TAL), as well as a higher level of ShA, free and cell wall-bound p-hydroxybenzoic acid, free homovanillic acid, free sinapic acid, and cell wall-bound syringic acid can be considered biochemical indicators of the dominance of the rye genome.

Recent advancement in OMICS approaches to enhance abiotic stress tolerance in legumes

The world is facing rapid climate change and a fast-growing global population. It is believed that the world population will be 9.7 billion in 2050. However, recent agriculture production is not enough to feed the current population of 7.9 billion people, which is causing a huge hunger problem. Therefore, feeding the 9.7 billion population in 2050 will be a huge target. Climate change is becoming a huge threat to global agricultural production, and it is expected to become the worst threat to it in the upcoming years. Keeping this in view, it is very important to breed climate-resilient plants. Legumes are considered an important pillar of the agriculture production system and a great source of high-quality protein, minerals, and vitamins. During the last two decades, advancements in OMICs technology revolutionized plant breeding and emerged as a crop-saving tool in wake of the climate change. Various OMICs approaches like Next-Generation sequencing (NGS), Transcriptomics, Proteomics, and Metabolomics have been used in legumes under abiotic stresses. The scientific community successfully utilized these platforms and investigated the Quantitative Trait Loci (QTL), linked markers through genome-wide association studies, and developed KASP markers that can be helpful for the marker-assisted breeding of legumes. Gene-editing techniques have been successfully proven for soybean, cowpea, chickpea, and model legumes such as Medicago truncatula and Lotus japonicus. A number of efforts have been made to perform gene editing in legumes. Moreover, the scientific community did a great job of identifying various genes involved in the metabolic pathways and utilizing the resulted information in the development of climate-resilient legume cultivars at a rapid pace. Keeping in view, this review highlights the contribution of OMICs approaches to abiotic stresses in legumes. We envisage that the presented information will be helpful for the scientific community to develop climate-resilient legume cultivars.

Carbon fluxes and environmental interactions during legume development, with a specific focus on Pisum sativum

Grain legumes are major food crops cultivated worldwide for their seeds with high nutritional content. To answer the growing concern about food safety and protein autonomy, legume cultivation must increase in the coming years. In parallel, current agricultural practices are facing environmental challenges, including global temperature increase and more frequent and severe episodes of drought stress. Crop yield directly relies on carbon allocation and is particularly affected by these global changes. We review the current knowledge on source-sink relationships and carbon resource allocation at all developmental stages, from germination to vegetative growth and seed production in grain legumes, focusing on pea (Pisum sativum). We also discuss how these source-sink relationships and carbon fluxes are influenced by biotic and abiotic factors. Major agronomic traits, including seed yield and quality, are particularly impacted by drought, temperatures, salinity, waterlogging, or pathogens and can be improved through the promotion of beneficial soil microorganisms or through optimized plant carbon resource allocation. Altogether, our review highlights the need for a better understanding of the cellular and molecular mechanisms regulating carbon fluxes from source leaves to sink organs, roots, and seeds. These advancements will further improve our understanding of yield stability and stress tolerance and contribute to the selection of climate-resilient crops.

Unravelling the treasure trove of drought-responsive genes in wild-type peanut through transcriptomics and physiological analyses of root

Peanut is one of the most valuable legumes, grown mainly in arid and semi-arid regions, where its production may be hindered by the lack of water. Therefore, breeding drought tolerant varieties is of great importance for peanut breeding programs around the world. Unlike cultivated peanuts, wild peanuts have greater genetic diversity and are an important source of alleles conferring tolerance/resistance to abiotic and biotic stresses. To decipher the transcriptome changes under drought stress, transcriptomics of roots of highly tolerant Arachis duranensis (ADU) and moderately susceptible A. stenosperma (AST) genotypes were performed. Transcriptome analysis revealed an aggregate of 1465 differentially expressed genes (DEGs), and among the identified DEGs, there were 366 single nucleotide polymorphisms (SNPs). Gene ontology and Mapman analyses revealed that the ADU genotype had a higher number of transcripts related to DNA methylation or demethylation, phytohormone signal transduction and flavonoid production, transcription factors, and responses to ethylene. The transcriptome analysis was endorsed by qRT-PCR, which showed a strong correlation value (R² = 0.96). Physio-biochemical analysis showed that the drought-tolerant plants produced more osmolytes, ROS phagocytes, and sugars, but less MDA, thus attenuating the effects of drought stress. In addition, three SNPs of the gene encoding transcription factor NFAY (Aradu.YE2F8), expansin alpha (Aradu.78HGD), and cytokinin dehydrogenase 1-like (Aradu.U999X) exhibited polymorphism in selected different genotypes. Such SNPs could be useful for the selection of drought-tolerant genotypes.

Genomics Associated Interventions for Heat Stress Tolerance in Cool Season Adapted Grain Legumes

Cool season grain legumes occupy an important place among the agricultural crops and essentially provide multiple benefits including food supply, nutrition security, soil fertility improvement and revenue for farmers all over the world. However, owing to climate change, the average temperature is steadily rising, which negatively affects crop performance and limits their yield. Terminal heat stress that mainly occurred during grain development phases severely harms grain quality and weight in legumes adapted to the cool season, such as lentils, faba beans, chickpeas, field peas, etc. Although, traditional breeding approaches with advanced screening procedures have been employed to identify heat tolerant legume cultivars. Unfortunately, traditional breeding pipelines alone are no longer enough to meet global demands. Genomics-assisted interventions including new-generation sequencing technologies and genotyping platforms have facilitated the development of high-resolution molecular maps, QTL/gene discovery and marker-assisted introgression, thereby improving the efficiency in legumes breeding to develop stress-resilient varieties. Based on the current scenario, we attempted to review the intervention of genomics to decipher different components of tolerance to heat stress and future possibilities of using newly developed genomics-based interventions in cool season adapted grain legumes.

The Adaptation and Tolerance of Major Cereals and Legumes to Important Abiotic Stresses

Abiotic stresses, including drought, extreme temperatures, salinity, and waterlogging, are the major constraints in crop production. These abiotic stresses are likely to be amplified by climate change with varying temporal and spatial dimensions across the globe. The knowledge about the effects of abiotic stressors on major cereal and legume crops is essential for effective management in unfavorable agro-ecologies. These crops are critical components of cropping systems and the daily diets of millions across the globe. Major cereals like rice, wheat, and maize are highly vulnerable to abiotic stresses, while many grain legumes are grown in abiotic stress-prone areas. Despite extensive investigations, abiotic stress tolerance in crop plants is not fully understood. Current insights into the abiotic stress responses of plants have shown the potential to improve crop tolerance to abiotic stresses. Studies aimed at stress tolerance mechanisms have resulted in the elucidation of traits associated with tolerance in plants, in addition to the molecular control of stress-responsive genes. Some of these studies have paved the way for new opportunities to address the molecular basis of stress responses in plants and identify novel traits and associated genes for the genetic improvement of crop plants. The present review examines the responses of crops under abiotic stresses in terms of changes in morphology, physiology, and biochemistry, focusing on major cereals and legume crops. It also explores emerging opportunities to accelerate our efforts to identify desired traits and genes associated with stress tolerance.