iTRAQ-based comparative proteomic response analysis reveals regulatory pathways and divergent protein targets associated with salt-stress tolerance in kenaf (Hibiscus cannabinus L.)

Kenafis an industrial crop for natural fibers and possesses salt-tolerant characteristics that can be used for phytoremediation; however, little is known about salt-induced proteomic changes in kenaf. In the present study, a comparative cytological, physiological, and proteomic analysis was performed on a salt-sensitive (P3B) and salt-tolerant (P3A) kenaf cultivars seedlings (21d old) under salt stress. The result showed P3A has more stable ultra-structure, larger gas exchange parameters (Pn, Gs, Tr, Ci), and higher chlorophyll contents (chl a, chl b) than P3B. Furthermore, a comparative iTRAQ-based quantitative proteomic analysis showed that 89 (74.78%) and 30 (25.2%) of differentially abundant proteins (DAPs) in P3A, and 133 (69.27%) and 59 (30.7%) in P3B, were up and down-accumulated (FC > 1.5, p< 0.05), respectively. Bioinformatics analysis revealed 160 and 146 Gene Ontology (GO) categories were significantly enriched. A total of 71 and 99 DAPs were mapped to 47 and 61 KEGG pathways in P3A and P3B, respectively, and 12 KEGG pathways were determined significantly enriched for each of the two cultivars. qRT-PCR results showed that transcript levels of several randomly selected genes had consistency with abundance levels of their corresponding proteins. DAPs including ATP, alpha-D-glucose-1-phosphate adenylyltransferase, aldehyde dehydrogenase (ALDH), ATP dependent Clp protease (clpB), glutathione S-transferase (GST), ATP synthase, and Photosystem II subunit S (PsBS) were found significantly higher in abundance in cultivar P3A than P3B and suggested to play essential roles in response to salt stress. Inclusively, these findings could likely shed light on the molecular mechanisms of salt stress tolerance in kenaf.