The CONSTANS-like gene family in wheat is involved in heading date and drought stress response

The CONSTANS-like (COL) zinc finger transcription factors are central regulators of the flowering pathway, linking the circadian clock to floral induction. However, their roles in abiotic stress responses remain unclear. Here, we identified 51 COL genes in common wheat, unevenly distributed between chromosomes and grouped into nine phylogenetic clades. Promoter analysis revealed abundant light-responsive cis-elements, followed by elements responsive to abscisic acid. Analysis of independent RNAseq datasets revealed that most members of the TaCOL gene family are expressed in multiple tissues and developmental stages, with preferential expression in leaves. Many TaCOLs including TaCOL-12/16/24/51, and their homoeologs, were drought responsive. Under hydroponic conditions, drought resulted in a reduction in TaCOL-03/12/22/27/33 expression, while expression of TaCOL-16/24/45/51 remained unchanged and TaCOL-08 upregulated. We also examined the physiological traits and expression rates of some TaCOLs in an early-maturing synthetic wheat-derived line (R16P1) and its parental cultivar, Pishgam, under drought stress. Drought significantly increased peroxidase and superoxide dismutase activities while reducing chlorophyll a, chlorophyll b, and carotenoid contents in both genotypes. However, these adverse effects were significantly less pronounced in R16P1. qPCR confirmed the drought-induced upregulation of some TaCOL genes, with higher expression in R16P1 line. These findings provide new insights into COL gene family's potential roles in wheat adaptation, highlighting candidates for genetic improvement of earliness and resilience to drought stress.