Abstract
Drought is one of the major impediments in wheat productivity. Traditional breeding and marker assisted QTL introgression had limited success. Available wheat genomic and RNA-seq data can decipher novel drought tolerance mechanisms with putative candidate gene and marker discovery. Drought is first sensed by root tissue but limited information is available about how roots respond to drought stress. In this view, two contrasting genotypes, namely, NI5439 41 (drought tolerant) and WL711 (drought susceptible) were used to generate ~78.2 GB data for the responses of wheat roots to drought. A total of 45139 DEGs, 13820 TF, 288 miRNAs, 640 pathways and 435829 putative markers were obtained. Study reveals use of such data in QTL to QTN refinement by analysis on two model drought-responsive QTLs on chromosome 3B in wheat roots possessing 18 differentially regulated genes with 190 sequence variants (173 SNPs and 17 InDels). Gene regulatory networks showed 69 hub-genes integrating ABA dependent and independent pathways controlling sensing of drought, root growth, uptake regulation, purine metabolism, thiamine metabolism and antibiotics pathways, stomatal closure and senescence. Eleven SSR markers were validated in a panel of 18 diverse wheat varieties. For effective future use of findings, web genomic resources were developed. We report RNA-Seq approach on wheat roots describing the drought response mechanisms under field drought conditions along with genomic resources, warranted in endeavour of wheat productivity.
Highlights
Drought is one of the major impediments in wheat productivity
Our study clearly reveals the mechanism of drought response by root tissues of wheat in soil, right from sensing of water deficiency by root, sensing of sucrose accumulation, intracellular signal transduction mediated by G-type lectin S-receptor-like serine/threonine-protein kinase SRK, ABA signalling along with salicylic acid pathway activation, oxidative stress response and reactive oxygen species (ROS) scavenging, energy balance, stomatal closure, regulation of cell wall, defense response and to the senescence (Table 4)
We report the molecular mechanism of wheat root drought responsiveness by irrigation withdrawal method using contrasting varieties at Zadok’s scale (Z24- Z37) scale which is critical for drought resilience
Summary
Drought is one of the major impediments in wheat productivity. Traditional breeding and marker assisted QTL introgression had limited success. Available wheat genomic and RNA-seq data can decipher novel drought tolerance mechanisms with putative candidate gene and marker discovery. Marker assisted selection (MAS) based on QTL linked markers has limited success in trait improvement[13] This is due to very limited number of efficient QTL having major effect on phenotypic variation. For successful use of QTL in selection program, it needs identification of specific polymorphism(s) which are having observed effect, QTL must be dissected into quantitative trait nucleotide (QTN) for more effective use[15] by alternative approach for marker discovery using transcriptomic approach. Drought adaptability mechanism in complex hexaploid genome needs interdisciplinary approach having water stress induced tissue specific phenotyping and its gene expression studies[16]. Such comparative studies of miRNAs of bread wheat and its ancestors are reported[21]
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