Whole-genome identification and expression analysis of basic leucine zipper genes under cadmium, drought and Orobanche cumana stresses in Helianthus annuus L.

The basic leucine zipper (bZIP) family of transcription factors (TFs) plays crucial role in response to different environment stresses. Helianthus annuus L. is one of the four major oil crops cultivated throughout the world. However, genome-wide characterization of bZIP genes and their evolution in sunflower has not been reported. In this study, we tried to identify 117 bZIP genes from H. annuus genome, which were unevenly distributed across 17 chromosomes. Evolutionary analysis indicated that HabZIPs could be divided into 12 groups (A, B, C, D, E, F, G, H, I, J, K and S) according to the phylogenetic relationship with those in Arabidopsis. Nevertheless, there was no HabZIP genes in group M, which included the homolog of AtbZIP74, indicating that this individual group was missing during the evolution of H. annuus. Collinearity analysis found 59 pairs of segmental duplicated genes, demonstrating that segmental duplication events played a crucial role in the expansion of HabZIP family. Moreover, we conducted the protein-protein interaction network prediction analysis to identify the key bZIP protein and other important TFs in sunflower which played significant roles in response to different stresses. The expression patterns of HabZIPs at different developmental stages of sunflower exhibited an organic-specific manner. Further, RNA-seq analysis showed that HabZIP21, HabZIP113, HabZIP84 and HabZIP76 were the most sensitive genes in response to cadmium, heat, cold, drought and salinity stresses. Expression patterns based on qRT-PCR showed that HabZIP16, HabZIP24, HabZIP40, HabZIP71 and HabZIP96 genes were specifically triggered in abiotic stresses i.e., cadmium, drought and biotic Orobanche cumana stress. This study provides insights into HabZIP gene family and their potential functions involved in growth, development and various stresses. This will facilitate further research on the bZIP gene family regarding their evolutionary history and biological functions.