Cotton transcriptome analysis reveals novel biological pathways that eliminate reactive oxygen species (ROS) under sodium bicarbonate (NaHCO3) alkaline stress

Abstract

Alkaline stress is one of the abiotic stresses limiting cotton production. Though RNA-Seq analyses, have been conducted to investigate genome-wide gene expression in response to alkaline stress in plants, the response of sodium bicarbonate (NaHCO₃) stress-related genes in cotton has not been reported. To explore the mechanisms of cotton response to this alkaline stress, we used next-generation sequencing (NGS) technology to study transcriptional changes of cotton under NaHCO₃ alkaline stress. A total of 18,230 and 11,177 differentially expressed genes (DEGs) were identified in cotton roots and leaves, respectively. Gene ontology (GO) analysis indicated the enrichment of DEGs involved in various stimuli or stress responses. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis showed that DEGs associated with plant hormone signal transduction, amino acid biosynthesis, and biosynthesis of secondary metabolites were regulated in response to the NaHCO₃ stress. We further analyzed genes enriched in secondary metabolic pathways and found that secondary metabolites were regulated to eliminate the reactive oxygen species (ROS) and improve the cotton tolerance to the NaHCO₃ stress. In this study, we learned that the toxic effect of NaHCO₃ was more profound than that of NaOH at the same pH. Thus, Na⁺, HCO₃^- and pH had a great impact on the growth of cotton plant. The novel biological pathways and candidate genes for the cotton tolerance to NaHCO₃ stress identified from the study would be useful in the genetic improvement of the alkaline tolerance in cotton.

Keywords: And secondary metabolites; Cotton; Differentially expressed genes (DEGs); NaHCO(3) stress; Reactive oxygen species (ROS); Transcriptome.