Breeding drought-resistant crops: G×E interactions, proteomics and pQTLS

The battle of crops against drought: Genetic dissection and improvement

With ongoing global climate change, water scarcity-induced drought stress remains a major threat to agricultural productivity. Plants undergo a series of physiological and morphological changes to cope with drought stress, including stomatal closure to reduce transpiration and changes in root architecture to optimize water uptake. Combined phenotypic and multi-omics studies have recently identified a number of drought-related genetic resources in different crop species. The functional dissection of these genes using molecular techniques has enriched our understanding of drought responses in crops and has provided genetic targets for enhancing resistance to drought. Here, we review recent advances in the cloning and functional analysis of drought resistance genes and the development of technologies to mitigate the threat of drought to crop production.

Effective Use of Water in Crop Plants in Dryland Agriculture: Implications of Reactive Oxygen Species and Antioxidative System

Under dryland conditions, annual and perennial food crops are exposed to dry spells, severely affecting crop productivity by limiting available soil moisture at critical and sensitive growth stages. Climate variability continues to be the primary cause of uncertainty, often making timing rather than quantity of precipitation the foremost concern. Therefore, mitigation and management of stress experienced by plants due to limited soil moisture are crucial for sustaining crop productivity under current and future harsher environments. Hence, the information generated so far through multiple investigations on mechanisms inducing drought tolerance in plants needs to be translated into tools and techniques for stress management. Scope to accomplish this exists in the inherent capacity of plants to manage stress at the cellular level through various mechanisms. One of the most extensively studied but not conclusive physiological phenomena is the balance between reactive oxygen species (ROS) production and scavenging them through an antioxidative system (AOS), which determines a wide range of damage to the cell, organ, and the plant. In this context, this review aims to examine the possible roles of the ROS-AOS balance in enhancing the effective use of water (EUW) by crops under water-limited dryland conditions. We refer to EUW as biomass produced by plants with available water under soil moisture stress rather than per unit of water (WUE). We hypothesize that EUW can be enhanced by an appropriate balance between water-saving and growth promotion at the whole-plant level during stress and post-stress recovery periods. The ROS-AOS interactions play a crucial role in water-saving mechanisms and biomass accumulation, resulting from growth processes that include cell division, cell expansion, photosynthesis, and translocation of assimilates. Hence, appropriate strategies for manipulating these processes through genetic improvement and/or application of exogenous compounds can provide practical solutions for improving EUW through the optimized ROS-AOS balance under water-limited dryland conditions. This review deals with the role of ROS-AOS in two major EUW determining processes, namely water use and plant growth. It describes implications of the ROS level or content, ROS-producing, and ROS-scavenging enzymes based on plant water status, which ultimately affects photosynthetic efficiency and growth of plants.

Application of Mass Spectrometry-Based Proteomics to Barley Research

Barley (Hordeum vulgare) is the fourth most cultivated crop in the world in terms of production volume, and it is also the most important raw material of the malting and brewing industries. Barley belongs to the grass (Poaceae) family and plays an important role in food security and food safety for both humans and livestock. With the global population set to reach 9.7 billion by 2050, but with less available and/or suitable land for agriculture, the use of biotechnology tools in breeding programs are of considerable importance in the quest to meet the growing food gap. Proteomics as a member of the "omics" technologies has become popular for the investigation of proteins in cereal crops and particularly barley and its related products such as malt and beer. This technology has been applied to study how proteins in barley respond to adverse environmental conditions including abiotic and/or biotic stresses, how they are impacted during food processing including malting and brewing, and the presence of proteins implicated in celiac disease. Moreover, proteomics can be used in the future to inform breeding programs that aim to enhance the nutritional value and broaden the application of this crop in new food and beverage products. Mass spectrometry analysis is a valuable tool that, along with genomics and transcriptomics, can inform plant breeding strategies that aim to produce superior barley varieties. In this review, recent studies employing both qualitative and quantitative mass spectrometry approaches are explored with a focus on their application in cultivation, manufacturing, processing, quality, and the safety of barley and its related products.

Proteomic and metabolomic analysis of desiccation tolerance in wheat young seedlings

Young wheat seedlings are desiccation tolerant and have the capacity to withstand long dehydration period. In this study, we characterized the proteome and metabolome of wheat seedlings during desiccation and after recovery. Functional classification of differentially identified proteins revealed dynamic changes in the number and abundance of proteins observed during stress and recovery. Desiccation resulted in a decline in the abundance of proteins associated with photosynthesis and carbohydrate reserves, along with an increase in the presence of proteins associated with stress and defense response, such as peroxiredoxins and antioxidant enzymes. Following recovery, the abundance of stress-responsive proteins returned either partially or completely to their baseline level, confirming their importance to the seedling's desiccation response. Furthermore, proteins involved in carbohydrate metabolism, as well as fructose-bisphosphate aldolase and fructokinase-2 and phosphorylated metabolites as the substrate or the end-product, showed the inverse pattern during desiccation and after re-watering. This may reflect the fact that plants maintained energy supply during stress to protect seedlings from further damage, and for use in subsequent recovery after rewatering period. This study provides novel insights into the molecular mechanisms underlying the desiccation tolerance of wheat seedlings, and paves the way for more detailed molecular analysis of this remarkable phenomenon.

iTRAQ-based proteomics reveals key role of γ-aminobutyric acid (GABA) in regulating drought tolerance in perennial creeping bentgrass (Agrostis stolonifera)

γ-Aminobutyric acid (GABA), a non-proteinaceous amino acid, modulates plant growth and stress tolerance. However, the potential role of GABA in regulating key metabolic pathways and stress-defensive proteins against drought in plants has never been explored. Creeping bentgrass (Agrostis stolonifera) plants were pretreated with or without GABA and then subjected to water stress for 8 days in controlled growth chambers (23/19 °C, day/night). Physiological analysis showed that elevated endogenous GABA level via exogenous GABA application significantly mitigated water stress damage to creeping bentgrass, as manifested by increased leaf relative water content, water use efficiency, osmotic adjustment (OA), photochemical efficiency (Fv/Fm), net photosynthetic rate, and reduced oxidative damage. iTRAQ-based proteomics found that enhanced chaperones accumulation, carbohydrates, amino acids, and energy metabolism played important roles in protein protection, OA, energy maintenance, and metabolic balance, which is important adaptive response to drought stress in creeping bentgrass. The GABA further promoted energy production and conversion, antioxidant defense, and DHN3 accumulation that were essential for energy requirement, ROS-scavenging, and the prevention of cell dehydration in leaf during drought stress. In addition, GABA-treated plants maintained significantly higher abundance of dicarboxylate transporter 2.1, ATP-dependent zinc metalloprotease, receptor-like protein kinase HERK1, o-acyltransferase WSD1, omega-6 fatty acid desaturase, and two-component response regulator ORR21 than untreated plants under drought stress. The result provides new evidences that GABA-induced drought tolerance is possibly involved in the improvement of nitrogen recycling, protection of photosystem II, mitigation of drought-depressed cell elongation, wax biosynthesis, fatty acid desaturase, and delaying leaf senescence in creeping bentgrass.