Comparative analysis of alfalfa (Medicago sativa L.) seedling transcriptomes reveals genotype-specific drought tolerance mechanisms

Abstract

BackgroundDrought is one of the main abiotic factors that affect alfalfa yield. The identi cation of genes that control this complex trait can provide important insights for alfalfa breeding. However, little is known about how alfalfa responds and adapts to drought stress, particularly in cultivars of differing drought tolerance. ResultsIn this study, the drought-tolerant cultivar Dryland 'DT' and the drought-sensitive cultivar WL343HQ 'DS' were used to characterize leaf and root physiological responses and transcriptional changes in response to water de cit. Under drought stress, Dryland roots (DTR) showed more differentially expressed genes than WL343HQ roots (DSR), whereas WL343HQ leaves (DSL) showed more differentially expressed genes than Dryland leaves (DTL). Many of these genes were involved in stress-related pathways, carbohydrate metabolism, and lignin and wax biosynthesis, which may have improved the drought tolerance of alfalfa. We also observed that several genes related to ABA metabolism, root elongation, peroxidase activity, cell membrane stability, ubiquitination, and genetic processing responded to drought stress in alfalfa. We highlighted several candidate genes, including sucrose synthase, xylan 1,4-betaxylosidase, primary-amine oxidase, and alcohol-forming fatty acyl-CoA reductase, for future studies on drought stress resistance in alfalfa and other plant species. ConclusionsIn summary, our results reveal the unique drought adaptation and resistance characteristics of two alfalfa genotypes. These ndings, which may be valuable for drought resistance breeding, warrant further gene functional analysis to augment currently available information and to clarify the drought stress regulatory mechanisms of alfalfa and other plants. HighlightsWe assembled leaf and root transcriptomes of drought-tolerant and drought-sensitive alfalfa cultivars under control and drought conditions.Under drought, the drought-tolerant cultivar exhibited more differentially expressed metabolites than the drought-sensitive cultivar.Genes associated with carbon metabolism, amino acid metabolism, hormones, and secondary metabolites were differentially expressed under drought stress.The drought-tolerant cultivar exhibited higher expression of genes encoding sucrose synthase, xylan 1,4-beta-xylosidase, primary-amine oxidase, and alcohol-forming fatty acyl-CoA.

Comparative physiological, transcriptomic, and WGCNA analyses reveal the key genes and regulatory pathways associated with drought tolerance in Tartary buckwheat

“…In many plants, the morphological and physiological indices highlight that the tolerant and susceptible genotypes respond differently to drought stress ( Dossa et al., 2017 ; Wang et al., 2018b ; Kumar et al., 2019 ; Harb et al., 2020 ; Ma et al., 2021 ; Wan et al., 2021 ; Waititu et al., 2021 ; Zhao et al., 2021 ; Zhang et al., 2021a ). For example, the RWC of the leaf of the tolerant genotype was higher and the wilting was slower compared with the susceptible genotype.…”

Regulation of Na+/H+ exchangers, Na+/K+ transporters, and lignin biosynthesis genes, along with lignin accumulation, sodium extrusion, and antioxidant defense, confers salt tolerance in alfalfa

“…Alfalfa provides beneficial impacts on sustainable agriculture, adds N 2 to the soils, increases organic matter, and decreases the reliance on N 2 fertilizers ( Song et al., 2021 ). Alfalfa shows superior tolerance to abiotic stresses, including drought, heat, and oxidative stress ( Matthews et al., 2019 ; Ma et al., 2021 ). Therefore, it might be used as a promising source of germplasms for molecular breeding with enhanced tolerance to multiple abiotic stresses.…”

Identification of QTL and candidate genes associated with biomass yield and Feed Quality in response to water deficit in alfalfa (Medicago sativa L.) using linkage mapping and RNA-Seq

“…Ascertaining the DEGs that change upon water stress in alfalfa is of crucial in understanding the genetic base of drought tolerance. In alfalfa, although drought-responsive DEGs have been reported in previous studies ( Ma et al., 2021 ; Singer et al., 2021 ), there were some limitations due to the lack of a reference genome. The release of a high-quality alfalfa reference genome has given new power to transcriptional analysis ( Chen et al., 2020b ).…”