HD-ZIP transcription factors: pivotal regulators of plant reproductive development

The HD-ZIP gene family, a group of plant-specific transcription factors, plays pivotal regulatory roles in various aspects of plant growth and development. Accumulating evidence has demonstrated the extensive involvement of HD-ZIP members in regulating reproductive developmental processes. This review systematically summarizes both the structural characteristics of the four HD-ZIP subfamilies (Ⅰ–Ⅳ) and their distinct regulatory roles in plant reproductive development. Recent studies reveal that a conserved HD-ZIP I clade serves as a core regulator of key reproductive processes, ranging from spike development in monocots (e.g., barley Vrs1 and maize GT1) to sex determination in dicots (e.g., cucumber CmHB40 and persimmon MeGI). Meanwhile, members of other subfamilies (HD-ZIP Ⅱ-Ⅳ) contribute significantly to diverse reproductive processes including pistil development, floral organ formation, and anther development, among others. This review provides a comprehensive synthesis of HD-ZIP subfamily functions in reproductive development, integrating current knowledge while highlighting critical research gaps. These insights aim to provide theoretical foundations for functional characterization and potential applications of HD-ZIP reproductive regulators, while advancing our understanding of transcriptional regulation mechanisms in plant reproductive development.