Among micronutrients, zinc serves predominantly as a cofactor of many enzymes involved in important biochemical reactions. Vigorous sunflower growth in response to zinc application points towards the existence of an efficient zinc transportation system in this crop. ZIP protein is responsible for the availability of zinc and iron in all plant cells. The absence of comprehensive ZIP gene characterization in sunflower was the driving force for conducting this research work. The objective of the current study was to explore and characterise all ZIP genes across the sunflower genome. A total of 19 ZIP genes were identified and designated as HaZIPs in ascending order. All 19 HaZIP proteins were predicted to exist in the plasma membrane. The HaZIPs family was clustered into 3 groups based on phylogenetic assessment. Not much diversity in structural features of genes belonging to the same group was observed; the genes belonging to different groups exhibited variations in motif configuration. The genes were unevenly mapped on 9 chromosomes, with the maximum genes (7) found on chromosome 15. Two paralog pairs showed segmental duplication, while tandem duplication was witnessed in 4 paralog pairs. Sunflower exhibited no phylogenetic association with other crops, except Arabidopsis thaliana, where a single ortholog was witnessed. Significant increase in expression of HaZIP-1, HaZIP-3, HaZIP-5 and HaZIP-19 was recorded upon exposure of sunflower to drought stress, compared to control, for all 1h, 3h, 6h and 9h. Overall, maximum expression of all 4 genes was witnessed after 3h treatment, while minimum expression was recorded after 9h exposure to drought stress. The cis-acting ABRE could be involved in higher expression of HaZIP genes under drought stress.
Zaman et al. (Tue,) studied this question.