Molecular characterization of CONSTANS-Like (COL) genes in banana (Musa acuminata L. AAA Group, cv. Grand Nain).

The CONSTANS (CO) family is an important regulator of flowering in photoperiod sensitive plants. But information regarding their role in day neutral plants is limited. We report identification of nine Group I type CONSTANS-like (COL) genes of banana and their characterization for their age dependent, diurnal and tissue-specific expression. Our studies show that the Group I genes are conserved in structure to members in other plants. Expression of these genes shows a distinct circadian regulation with a peak during light period. Developmental stage specific expression reveals high level transcript accumulation of two genes, MaCOL3a and MaCOL3b, well before flowering and until the initiation of flowering. A decrease in their transcript levels after initiation of flowering is followed by an increase in transcription of other members that coincides with the continued development of the inflorescence and fruiting. CO binding cis-elements are observed in at least three FT -like genes in banana suggesting possible CO-FT interactions that might regulate flowering. Distinct tissue specific expression patterns are observed for different family members in mature leaves, apical inflorescence, bracts, fruit skin and fruit pulp suggesting possible roles other than flowering. This is the first exhaustive study of the COL genes belonging to Group I of banana.