Abstract
Globally, sodicity is one of the major abiotic stresses limiting the wheat productivity in arid and semi-arid regions. With due consideration, an investigation of the complex gene network associated with sodicity stress tolerance is required to identify transcriptional changes in plants during abiotic stress conditions. For this purpose, we sequenced the flag leaf transcriptome of a highly tolerant bread wheat germplasm (KRL 3–4) in order to extend our knowledge and better understanding of the molecular basis of sodicity tolerance. A total of 1,980 genes were differentially expressed in the flag leaf due to sodicity stress. Among these genes, 872 DEGs were upregulated and 1,108 were downregulated. Furthermore, annotation of DEGs revealed that a total of 1,384 genes were assigned to 2,267 GO terms corresponding to 502 (biological process), 638 (cellular component), and 1,127 (molecular function). GO annotation also revealed the involvement of genes related to several transcription factors; the important ones are expansins, peroxidase, glutathione-S-transferase, and metal ion transporters in response to sodicity. Additionally, from 127 KEGG pathways, only 40 were confidently enriched at a p-value <0.05 covering the five main KEGG categories of metabolism, i.e., environmental information processing, genetic information processing, organismal systems, and cellular processes. Most enriched pathways were prioritized using MapMan software and revealed that lipid metabolism, nutrient uptake, and protein homeostasis were paramount. We have also found 39 SNPs that mapped to the important sodicity stress-responsive genes associated with various pathways such as ROS scavenging, serine/threonine protein kinase, calcium signaling, and metal ion transporters. In a nutshell, only 19 important candidate genes contributing to sodicity tolerance in bread wheat were identified, and these genes might be helpful for better understanding and further improvement of sodicity tolerance in bread wheat.
Highlights
Achieving global food security in the 21st century seemed arduous due to acute environmental challenges including extreme climatic vulnerability (Fujimori et al, 2019) and persistent land degradation (Subramaniam and Masron, 2021)
In order to understand the mechanism involved at the transcriptional level for sodicity stress tolerance, transcriptome analysis was carried out for control and treated samples of wheat flag leaves
97.60%–99.06% of reads are mapped to the wheat reference genome (IWGSC RefSeq v1.0, http://www. wheatgenome.org/), whereas GC content varied from 51% to 53% for the control and sodicity stress treated samples (Table 1)
Summary
Achieving global food security in the 21st century seemed arduous due to acute environmental challenges including extreme climatic vulnerability (Fujimori et al, 2019) and persistent land degradation (Subramaniam and Masron, 2021). Salts excess sodium ions affected land degradation distorted nearly 1,128 million ha (Mha) land and causing US$ 27.3 billion economic losses per year (Qadir et al, 2014). Neoteric projections indicated that ~12 Mha of productive land salinized every year by the dint of natural and anthropogenic processes, and more than half of the total croplands is to be expectedly salinized by 2050 (UNCCD, 2017). Bread wheat (Triticum aestivum L.), is the staple food for nearly 2.5 billion of the world population, and constitutes a major share in carbohydrates (55%) and food calorie (20%) consumption in dietary intake (Ramadas et al, 2020). An extensive assessment of production loss in wheat cultivated in salt-affected soils revealed 20%–43% yield penalty, only due to adverse soil constraints (Qadir et al, 2014; Chaurasia et al, 2021)
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