Transcriptome analysis of upland cotton revealed novel pathways to scavenge reactive oxygen species (ROS) responding to Na(2)SO(4) tolerance

Salinity is an extensive and adverse environmental stress to crop plants across the globe, and a major abiotic constraint responsible for limited crop production threatening the crop security. Soil salinization is a widespread problem across the globe, threatening the crop production and food security. Salinity impairs plant growth and development via reduction in osmotic potential, cytotoxicity due to excessive uptake of ions such as sodium (Na(+)) and chloride (Cl(−)), and nutritional imbalance. Cotton, being the most cultivated crop on saline-alkaline soils, it is of great importance to elucidate the mechanisms involved in Na(2)SO(4) tolerance which is still lacking in upland cotton. Zhong 9835, a Na(2)SO(4) resistant cultivar was screened for transcriptomic studies through various levels of Na(2)SO(4) treatments, which results into identification of 3329 differentially expressed genes (DEGs) in roots, stems and leave at 300 mM Na(2)SO(4) stress till 12 h in compared to control. According to gene functional annotation analysis, genes involved in reactive oxygen species (ROS) scavenging system including osmotic stress and ion toxicity were significantly up-regulated, especially GST (glutathione transferase). In addition, analysis for sulfur metabolism, results in to identification of two rate limiting enzymes [APR (Gh_D05G1637) and OASTL (Gh_A13G0863)] during synthesis of GSH from SO(4)(2−). Furthermore, we also observed a crosstalk of the hormones and TFs (transcription factors) enriched in hormone signal transduction pathway. Genes related to IAA exceeds the rest of hormones followed by ubiquitin related genes which are greater than TFs. The analysis of the expression profiles of diverse tissues under Na(2)SO(4) stress and identification of relevant key hub genes in a network crosstalk will provide a strong foundation and valuable clues for genetic improvements of cotton in response to various salt stresses.