Expression Profiling and Characterization of HcTGA5 Gene in Kenaf Under Hormonal Treatments and Its Association with Resistance to Root-Knot Nematode.

Kenaf (Hibiscus cannabinus L.), a member of the Malvaceae family, has gained increasing research interest owing to its therapeutic attributes. Among pathogens affecting tropical kenaf cultivation, Meloidogyne enterolobii is the most economically destructive disease, causing severe yield loss and quality deterioration. Consequently, the identification of M. enterolobii-resistant kenaf germplasms and the elucidation of the underlying molecular pathways are primary objectives for plant breeders. In this study, the gene encoding a TGA-like protein associated with root-knot nematode resistance was cloned from kenaf via reverse transcription polymerase chain reaction (RT-PCR) and the rapid amplification of cDNA ends (RACE), and designated as HcTGA5 gene. The full-length cDNA is 798 bp, encoding a 230-amino acid protein (GenBank accession: PZ944973). The application of phytohormones (jasmonic acid, JA; salicylic acid, SA; ethylene, ET) profoundly affected HcTGA5 gene expression with specific temporal patterns: peak expression was observed at 6 h after ET treatment, followed by 48 h after SA, and 24 h after JA treatment. HcTGA5 gene demonstrated an 'initial upregulation followed by decline' trend in response to ET treatment, whereas SA and JA triggered a 'rise-fall-rise' fluctuation. The data demonstrate the temporal modulation of HcTGA5 gene expression by phytohormones, suggesting its function in hormone-mediated defense signaling. A comparative analysis revealed markedly elevated HcTGA5 gene expression in M. enterolobii-resistant germplasms compared to susceptible ones, indicating its possible association with nematode resistance. In conclusion, HcTGA5 gene may play an integral role in kenaf's defense against M. enterolobii. The study establishes a basis for investigating the nematode resistance mechanisms of kenaf and gives a theoretical framework for the genetic enhancement and disease management of kenaf.