Genome-wide identification and expression analysis of HD-ZIP gene family in sunflower (Helianthus annuus L.) under water deficit stress

The HD-ZIP gene family plays a crucial role in plant growth, development, and responses to environmental stressors. Nevertheless, there exists a paucity of information regarding this gene family in Helianthus annuus (Sunflower). In the present investigation, a total of 55 putative HaHD-ZIP genes were identified and subsequently classified into four subfamilies based on phylogenetic analysis, further substantiated through the analysis of gene structures and conserved motifs. An analysis of the promoter regions of HaHD-ZIP genes revealed the existence of numerous diverse cis-regulatory elements. Furthermore, we identified 15,577 binding sites for the HD-ZIP transcription factor within the sunflower genome, distributed across 9,479 unique genes. The analysis of protein-protein interactions elucidated the existence of three distinct clusters of HaHD-ZIPs, within which A0A251U614, HaHD-ZIP48, and LBD1 proteins were identified as the most interactive proteins. Additionally, gene duplication analysis revealed that two genes were tandem duplicated, while eight genes were subjected to segmental duplication, underscoring the importance of these genes in the expansion of the HD-ZIP gene family. Expression analysis indicated notable upregulation of the HaHD-ZIP4 gene compared to other analyzed genes under water deficit stress conditions. The results will provide significant insights into the further functional characterization of drought-responsive HaHD-ZIP genes in Sunflower.