CONSTANS-like 13 homologs MiCOL13 A and MiCOL13B orchestrate flowering time and salt-drought tolerance in mango.

Abstract

The CO/COL gene family serves as a central regulator of photoperiod-dependent floral transition and exhibits functional diversification in plant adaptation to abiotic stress conditions. Through comprehensive analysis of the genomic data from the mango cultivar Guire 82 (Mangifera indica L.), two COL13 homologs, designated MiCOL13 A and MiCOL13B, were successfully characterized. Phylogenetic categorization revealed that MiCOL13 A and MiCOL13B cluster within evolutionary clade III of the CONSTANS-like superfamily. These two homologous genes displayed a circadian rhythm and were strongly expressed in the leaves throughout the flowering induction phase. Under short-day (SD) conditions, the flowering time of Arabidopsis strains overexpressing MiCOL13 A and MiCOL13B was significantly delayed. However, overexpression of MiCOL13 A promoted early flowering in Arabidopsis, and MiCOL13B delayed flowering under long-day (LD) conditions. Subcellular localization demonstrated that the nucleus was the location of MiCOL13 A and MiCOL13B. The study also revealed that the overexpression of MiCOL13 A and MiCOL13B enhances Arabidopsis resistance to salt and drought stresses, resulting in overexpressing lines with longer roots and higher survival rates. Investigations of physiological and biochemical parameters revealed that elevated expression of MiCOL13 A/B significantly upregulated the expression of stress-responsive endogenous genes in A. thaliana under saline and drought conditions. Moreover, yeast two-hybrid (Y2H) and bimolecular fluorescence complementation (BiFC) analyses revealed that the MiCOL13A and MiCOL13B proteins interact with two stress-related proteins, zinc finger protein 4 (MiZFP4) and MYB30-INTERACTING E3 LIGASE 1 (MiMIEL1). Together, our findings indicate that MiCOL13 A and MiCOL13B have dual functions in controlling flowering and responding to abiotic stress in plants.