Whole-Genome Analysis of ZF-HD Genes among Three Dendrobium Species and Expression Patterns in Dendrobium chrysotoxum

Abstract

ZF-HD transcription factors, which are unique to land plants, are involved in the regulation of abiotic stress response and related signaling pathways, and play a crucial role in plant growth and development. Dendrobium is one of the largest genera of orchids, with a high ornamental and ecological value. However, the specific functions of the ZF-HDs in Dendrobium remain unknown. In this study, we identified a total of 53 ZF-HDs from D. chrysotoxum (17), D. catenatum (23), and D. huoshanense (13), and analyzed their physicochemical properties, phylogenetic relationships, chromosomal locations, protein structures, conserved motifs, and expression patterns. The phylogenetic relationships revealed that 53 ZF-HDs were classified into six subfamilies (ZHDI–V and MIF), and all ZF-HD proteins contained motif 1 and motif 4 conserved domains, while a minority of these proteins had exons. The analysis of cis-elements in the promoters of ZF-HDs from three Dendrobium species showed that growth- and development-related elements were the most prevalent, followed by hormone response and abiotic stress response elements. Through collinearity analysis, 14 DchZF-HDs were found to be collinear with DhuZF-HDs, and 12 DchZF-HDs were found to be collinear with DcaZF-HDs. Furthermore, RT-qPCR analysis revealed that DchZF-HDs play a regulatory role in the development of lateral organs during the flowering process. The results indicated that DchZHD2 plays a role in the unpigmented bud stage, while DchMIF8 and DchZHD16 play significant roles during the pigmented bud and initial bloom stages. Hence, this study provides a crucial basis for further exploring ZF-HDs functions in regulating the floral organs of orchids.