[Interaction of the BRACTEA gene with the TERMINAL FLOWER1, LEAFY, and APETALA1 genes during inflorescence and flower development in Arabidopsis thaliana]

Abstract

The major Arabidopsis thaliana genes controlling the shoot architecture are TERMINAL FLOWER1 (TFL1), APETALA1 (AP1), and LEAFY (LFY). The BRACTEA (BRA) gene also codes for one of the key regulators of inflorescence development. The bra tfl1-11, bra lfy-5, and bra ap1-20 double mutants were analyzed morphologically, and expression of the TFL1, AP1, and LFY genes was studied in the bra mutant and wild-type plants. The BRA gene was found to positively regulate the TFL1 and AP1 genes after floral initiation, determining more than 70% of their total expression level. In floral meristem, the BRA gene prevented AP1 expression, restricting AP1 transcription to the perianth zone. Since flowers were completely converted into vegetative shoots in the bra lfy-5 double mutant, it was assumed that the BRA and LFY genes function redundantly and independently in floral initiation. The results demonstrate that BRA is one of the genes that determine the balance between maintenance of proliferative activity in apical meristem and floral development in its peripheral region; such a balance is necessary for indeterminate inflorescence development.