Comparative Physiological and Transcriptomic Analysis Provide New Insights of Crucial Pathways and Genes Regulating Kenaf Salt Tolerance

Soil salinity is one of the most challenging issue for sustainable crop productivity worldwide, and kenaf is an important natural fiber crop with considerable salt tolerance. However, little is known about the molecular mechanisms in kenaf salt tolerance. In this study, 60 kenaf cultivars were screened for salt tolerance, and after analysis of agronomic and physiological indexes, cultivar CP018 and CP047 were found to have the highest and the lowest salt tolerance, respectively. This was mainly demonstrated in the lower root MDA content of 26.78% in CP018 compared to 29.76% in CP047, while the enzyme activities of SOD, POD, and CAT were mostly higher in CP018 than in CP047. Then using these two cultivars CP018 and CP047 as representing salt-tolerant and salt-sensitive cultivars, further global gene expression analysis responses to salt stress were conducted under control (0-mM NaCl) and salt stress (200-mM NaCl) conditions. The result indicated 11,677 (6538 up- and 5139 down-regulated) and 11,764 (6159 up- and 5605 down-regulated) differentially expressed genes (DEGs) in CP018 and CP047, respectively. Transcription factors including WRKY, LBD, HSF, and NAC, most of which were up-regulated in CP018 compared with CP047. KEGG enrichment analysis identified significantly different gene expression related to metabolic pathways, such as ROS scavenging, sucrose and starch metabolism, plant hormone signal transduction, cysteine and methionine metabolism, phenylpropane, and flavonoid biosynthesis in both cultivars, and these pathways may be partly responsible for the differences in salt tolerance between CP018 and CP047. These findings may help to elucidate the molecular mechanisms of salt tolerance in kenaf.

Automated summary

This study screened 60 kenaf cultivars for salt tolerance, and identified CP018 as salt-tolerant and CP047 as salt-sensitive cultivars. Further gene expression analysis showed significant differences in the expression of genes related to metabolic pathways between CP018 and CP047 under salt stress. These findings contribute to the understanding of the molecular mechanisms of salt tolerance in kenaf.