FLOWERING TIME GENE ANALOGUES IN MUSA

Abstract

In Musa, a mayor problem for somatic embryogenesis is the estimation of flower transition. In some species, the timing of flowering is primarily influenced by environmental factors, photoperiod, light quality and quantity, vernalization, and nutrient and water availability. Other species like bananas and plantains are less sensitive to environmental variables and appear to flower in response to internal cues such as plant size or number of vegetative nodes. In Musa, the number of leaves is a critical factor to flowering. Decapitated plants with less than 10 leaves return to initial state at first leaf emitted, after that the flowering process is irreversible (Belalcazar, 1994). Genetic analysis of flowering time in pea, cereals, and Arabidopsis supports the hypothesis that the transition to flowering is under multifactorial control (Koornneef et al., 1998). These genetic and molecular studies have revealed an evolutionarily conserved network. Comparative gene expression studies between the families Brassicaceae (Arabidopsis), Scrophulariaceae (Antirrhinum) and Solanaceae (Petunia) indicate strong conservation of floral developmental gene functions across broad taxonomic levels (Bernier and Perilleux, 2005). In Musa, no information about flower genes has been reported. Based on conserved motif of FLT, CO, GAI, of flowering time genes of rice and Arabidopsis, our group designed degenerated primers using CODEHOP software (Rose et al., 1998). Based on theoretical size, we cloned, and sequenced PCR fragments amplified with degenerated primers. Sequence analysis with ClustalW show three different FLT, five GAI and one CO sequences. Genes CO, GAI and FLT have 59, 69 and 83% of identical amino acids, respectively, to orthologues in Oryza. We are attempting to sequence additional genes like GaMyb, GA3ox, GA20ox, Della to perform expression analyses of these analogues with real time PCR, in Musa shoot tips at different vegetative and floral stages.