Abstract
BACKGROUND: Sunflower (Helianthus annuus L.) is widely cultured in globally tropical and subtropical regions, with better resistance to various abiotic stresses as a model crop. Despite the fact that zinc finger-homeodomain (ZF-HD) genes play an important role in responding to plant growth, development and stress resistance across the multiple species, the evolutionary history and abiotic function of the ZF-HD gene family in sunflower remain largely unexplored. RESULTS: In this study, we identified 15 HaZF-HD genes (designated as HaZF1-HaZF15) in the sunflower genome, and they were divided into MIF and ZHD subfamilies. The proteins from the same group were similar in conserved motifs and domains, such as motif 1 and motif 3, constituting the ZF domain, were almost existed in 15 HaZF-HD proteins. Motif 2 (HD domain) was specifically presented in the ZHD subfamily. Collinearity analysis revealed that 5 pairs of genes with fragment duplication contributed to the expansion of HaZF-HD gene family. The analysis of cis-acting element demonstrated that the response elements related the hormone response and abiotic/biotic stress were the most prevalent, followed by plant growth and development elements. In the tissue expression profile, HaZF-HD gene family had the highest expression in leaves and floral organs. Additionally, RNA-seq and RT-qPCR analysis revealed HaZF3 responded positively in the initial stage of drought stress, whereas a prompt and significant decrease of relative expression value in response to salt stress was showed in HaZF6 and HaZF9. CONCLUSIONS: Overall, this study enhances our comprehension of the function of ZF-HD genes in positive regulation of responsiveness to abiotic stress and provide key candidate genes for sunflower stress resistance breeding.