Genome-wide identification of bHLH transcription factors in Kenaf (Hibiscus cannabinus L.) and gene function analysis of HcbHLH88

Among plants' transcription factor families, the bHLHs family has a significant influence on plant development processes and stress tolerance. However, there have been no relevant studies performed on the bHLHs family in kenaf (Hibiscus cannabinus L). Here, the bHLH transcription factors in kenaf were found using bioinformatics, and a total of 141 kenaf HcbHLH transcription factors were identified. Phylogenetic analysis revealed that these transcription factors were irregularly distributed on 18 chromosomes and separated into 20 subfamilies. Additionally, utilizing the transcriptome data under diverse abiotic pressures, the expression of HcbHLH members was analyzed under different stress conditions. A typical HcbHLH abiotic stress transcription factor, HcbHLH88, was exposed to salt, drought, heavy metals, and ABA. The findings revealed that HcbHLH88 might be activated under salt, drought, cadmium stress, and ABA conditions. Furthermore, HcbHLH88's function under salt stress conditions was studied after it was silenced using the virus-induced gene silencing (VIGS) technique. Reduced antioxidant enzyme activity and stunted plant development were seen in VIGS-silenced seedlings. Stress-related genes were shown to be considerably downregulated in the HcbHLH88-silenced kenaf plants, according to the qRT-PCR study. In conclusion, this study provides the first systematic gene family analysis of the kenaf bHLH gene family and provides a preliminary validation of the salt tolerance function of the HcbHLH88 gene. This study lays the foundation for future research on the regulatory mechanisms of bHLH genes in response to abiotic stresses.