Genome-wide characterization of GRF-GIF transcriptional modules in kenaf (Hibiscus cannabinus L.) reveals their roles in plant development and multi-stress adaptation.

Growth regulatory factors (GRFs) are pivotal regulators of plant growth, development, and stress responses, functioning synergistically with GRF-interacting factors (GIFs) as transcriptional co-activators. Despite their characterization in diverse plants, GRF and GIF families remain unstudied in kenaf (Hibiscus cannabinus). Here, 33 HcGRF and 7 HcGIF genes were systematically identified from the kenaf genome. Phylogenetic analysis classified HcGRF into 10 subgroups (11 in clade F) and HcGIF into 3 subgroups. Promoter cis-element analysis revealed enrichment in abiotic stress response elements, light-response elements, and hormone response elements in the GRF and GIF promoter region. Based on RNA-Seq data, tissue-specific expression profiling demonstrated predominant accumulation of most HcGRFs (notably HcGRF3 and HcGRF21) and HcGIF1 in leaves and buds, and that the expression of HcGRF3, HcGFR21, and HcGIF1 was 5-fold, 14.7-fold, and 11.3-fold higher than that of leaves, respectively, suggesting that they play a central role in the regulation of growth regulation. Transcriptome-wide interrogation under chromium, salinity, cadmium, and drought stresses revealed spatiotemporal expression divergence. qRT-PCR confirmed that HcGRF3 expression increased gradually under salt/drought stress, while HcGRF21 and HcGIF1 peaked at 12 h. Subcellular localization confirmed nuclear targeting of these genes. In addition, physiological and biochemical analyses through functional validation by VIGS and transgenic Arabidopsis thaliana showed that salt and drought tolerance of kenaf was reduced by gene silencing, whereas overexpression plants showed stronger tolerance. The novelty and significance of these findings for kenaf on the roles of HcGRFs and HcGIFs genes in the growth, development, and abiotic stresses.