Transcriptional and Post-transcriptional Gene Regulations under Salt-Stress in Wheat

Abstract

Environmental stressors, including salt stress, reduce significantly cereal crop productivity worldwide, challenging the world's food security. Developing cereal crop varieties that are tolerant to salt stress is required to meet food needs in the future. To attain this goal, understanding the mechanisms underpinning plant responses to salt stress is a pre-requisite. Wheat (Triticum aestivum) is widely considered a moderately salt-tolerant species; however, the level of tolerance and the responses that bring about tolerance to salinity vary among different wheat tissues and cultivars. The present study aimed at investigating the main physiological, biochemical and molecular responses to salt stress in different wheat cultivars. Differential responses to salinity were characterised in roots and shoots of three Saudi wheat cultivars including Najran, Mebiah and Qiadh. Results showed that the three wheat cultivars displayed different growth and metabolic and antioxidant responses where Najran wheat exhibited lesser effect of salt on growth and yield and higher accumulation of metabolites and antioxidants in response to the stress. Based on this finding, global profiling of salt-induced changes in the root and shoot transcriptomes as well as salt-induced changes in alternative splicing of pre-mRNA were conducted in Najran wheat. Results revealed that roots respond to a higher extent than shoots to salt stress and that salt-stress induces responses that are organ specific as well as responses that are common to roots and shoots. Salt stress induced genes that are involved in glutathione metabolism (e.g. GST) and biosynthesis of secondary metabolites such as phenylpropanoids (e.g. PAL) and galactose metabolism (e.g. INV) suggesting that these genes might participate in wheat salt tolerance. In addition, exposing plants to 200 mM NaCl slightly increased the number of AS events by 1.6% and 0.5% in the roots and shoots, respectively, indicating the potential involvement of post-transcriptional regulation in salt tolerance. Functional enrichment analysis show that a cysteine-type endopeptidase inhibitor was the most significantly enriched term of DSGs shared between the roots and shoots of Najran wheat suggesting that control of proteolysis might participate in the salt-tolerance exhibited in this cultivar.