Genome-wide Identification of the HD-ZIP IV Gene Family in Pogostemon cablin and Its Association with Glandular Hair Development

Shuqi Xie^1*Yilin Li¹Huiting Liao¹Wenyi Chen¹Yuqi Zhang¹Xiaoming Yan²Hongyi Zhang¹Mengling He¹Hanjing Yan^1*

• ¹Guangdong Pharmaceutical University, Guangzhou, China
• ²Guangdong Institute for Drug Control (GDIDC), Guangzhou, China

HD-ZIP IV transcription factors are members of the plant-specific homeodomain-leucine zipper (HD-ZIP) family, which plays a role in the development of epidermal cells. While this gene family has been extensively studied in various plants, its function in Pogostemon cablin (patchouli) is not yet fully understood. In this research, a comprehensive genome-wide analysis of patchouli was conducted, leading to the identification of 38 HD-ZIP IV family members, named PcHDZIV1 to PcHDZIV38.Phylogenetic and synteny analyses grouped these genes into six subfamilies. The analysis of gene structure demonstrated that intron/exon arrangements are highly conserved within each subfamily. Promoter cis-element analysis indicated that patchouli HD-ZIP IV genes are widely involved in light response, hormone signaling, and stress responses, particularly in relation to hormones such as ABA, MeJA, and IAA. Most PcHDZIV genes exhibited significant dynamic responses to exogenous hormone treatments (e.g., MeJA, IAA, and SA). For example, PcHDZIV5 was upregulated during the 3 to 12-hour treatment with MeJA and IAA, and also showed increased expression at 48 hours post-SA treatment. Furthermore, correlation analysis between gene expression levels and glandular trichome density, along with virus-induced gene silencing (VIGS) assays, demonstrated that PcHDZIV5 plays a critical role in patchouli glandular trichome development. By integrating gene expression patterns following hormone treatments, the findings further suggest that hormone signaling may regulate the transcription of PcHDZIV5, thereby indirectly promoting glandular trichome development. This study provides a foundation for the functional characterization of HD-ZIP IV genes in patchouli and offers valuable insights into the molecular mechanisms underlying glandular trichome development.