Comparative Transcriptomics of Two Contrasting Cultivars and Functional Verification of HcWRKY70 for Salt Tolerance in Kenaf (Hibiscus Cannabinus L.)

Salt stress is a major global challenge that significantly hinders plant growth and reduces crop yields. Kenaf (Hibiscus cannabinus L.) is a valuable stem fiber crop increasingly cultivated in saline and alkaline soils. However, the molecular basis of kenaf's tolerance to saline stress during the germination phase of seeds has remained largely unexplored. In this study, we performed a comprehensive transcriptomic analysis on two contrasting kenaf cultivars, Fuhong 952 (salt-tolerant) and Zanyin No. 1 (salt-sensitive), under salt stress conditions during seed germination. The results revealed a total of 9,232 and 13,982 differentially expressed genes (DEGs) in Fuhong 952 and Zanyin No. 1, respectively, with the number of DEGs increasing with the duration of salt treatment. Hierarchical clustering of DEGs in both cultivars across various time points (3, 24, and 72 h) identified distinct co-expressed gene clusters corresponding to different phases of the salt stress response. The identified DEGs were implicated in maintaining ionic and membrane homeostasis and transcriptional regulation in salt stress responses. The verification of twelve DEGs through qRT-PCR confirmed the reliability of our RNA-sequencing data. Furthermore, virus-induced gene silencing of a salt-responsive gene HcWRKY70 resulted in a 36.90% decrease in plant height, a 2.3-fold elevation in Malondialdehyde (MDA) levels, and a 43.70% reduction in Catalase (CAT) activity under salt stress, suggesting that HcWRKY70 plays a crucial role in regulating both growth and oxidative stress responses in kenaf. Overall, this study elucidates significant understandings regarding the molecular mechanisms underlying salinity stress tolerance in kenaf. The identified genes, including HcWRKY70, could serve as valuable targets for breeding salt-tolerant kenaf cultivars by modulating key stress-responsive pathways and enhancing tolerance traits.