Overexpression of the mango MiCO gene delayed flowering time in transgenic Arabidopsis

CONSTANS (CO)/CONSTANS-like (COL) genes play an important role in the photoperiodic flowering pathway. However, the functional roles of the CO/COL genes in mango (Mangifera indica L.) remain unknown. In this study, the MiCO gene was isolated from mango and functionally characterized. The open reading frame is 966 bp in length and encodes 322 amino acids; the protein contains two conserved B-box zinc finger domains and a CCT domain and thus belongs to the CO/COL group I protein family. The MiCO protein fused to green fluorescent protein localized to the nucleus. MiCO was expressed in all tested organs and was highly expressed especially in the leaves and stems of nonflowering branches, but its expression decreased in flowering branches. The expression level of MiCO significantly increased during the transition from vegetative to reproductive growth. MiCO was also expressed in accordance with the circadian rhythm, with the greatest expression level detected at 09:00. Overexpression of MiCO in Arabidopsis significantly delayed flowering under both long-day and short-day conditions.