Expansion of CONSTANS-like genes in sunflower confers putative neofunctionalization in the adaptation to abiotic stresses

Abstract

CONSTANS-like (COL) genes play crucial roles in the regulation of photoperiodic flowering and responses to biotic and abiotic stresses; however, COL genes in sunflower (HaCOL) have not been extensively studied. In the present study, we identified 22 putative HaCOL genes in the whole genome sequence of sunflower, which were unevenly distributed on 10 chromosomes. The phylogenetic analysis showed that the HaCOLs could be divided into three well-defined groups (groups I, II and III). Group III had the highest number of COL genes among the three tested monocots, while the highest number of COL genes were observed in group I among the five tested dicots. Among all eight species, group II had the fewest COL family members. Segmental duplications contributed greatly to the expansion of this gene family. Furthermore, 11 tissue expression profiles of 22 HaCOL genes were analyzed through RNA-seq, which displayed their tissue-specific expression profiles. In addition, the expression levels of these HaCOL genes were analyzed under hormone, cadmium (Cd), heat, and drought stresses, and the results showed that HaCOL3, HaCOL6, and HaCOL19 were more sensitive than other HaCOLs to certain abiotic stresses. Moreover, the duplicated genes conferred important neofunctionalization in response to abiotic stresses. On the basis of our findings, we speculate that this conserved, duplicated and neofunctionalized COL gene family may play pivotal roles in the adaptation of sunflower to adverse environments.