BdiRCN4 regulates meristem fate in Brachypodium distachyon

MACHADO, R; MUCHUT, SE; REUTEMANN, AG; VEGETTI, AC; UBERTI-MANASSERO, NG

Córdoba

Congreso; LII REUNION ANUAL DE LA SOCIEDAD ARGENTINA DE BIOQUIMICA Y BIOLOGIA MOLECULAR (SAIB); 2016

In higher plants, a phase transition from vegetative to reproductive development is tightly coordinated through networks that integrate internal and external stimuli. TERMINAL FLOWER1 (TFL1) controls flowering time and inflorescence architecture in Arabidopsis thaliana, acting as a negative regulator of the phase changes of the shoot apical meristem (SAM) from vegetative to inflorescence meristem (IM), and from IM to floral meristem. Here we show functional analyses of BdiRCN4, homologue to TFL1 in Brachypodium distachyon. Arabidopsis plants expressing the 35SCaMV::BdiRCN4 construct show a strong delay in SAM to IM transition, as well as a longer maintenance of the IM, leading to a longer life cycle compared to wild type. These plants also exhibit a highly branched inflorescence shoot and bracts instead of flowers, which correlates with lower expression levels of the ABCDE genes LFY, AP1and PI. Some of these inflorescences eventually develop fertile flowers. In Brachypodium, insertional mutants carrying a 4xCaMV35S enhancer sequence display a similar phenotype. Higher expression levels of BdiRCN4 promote extended vegetative phase and few or absent production of spikelets. These results suggest that BdiRCN4 acts as floral repressor. Furthermore, function of TFL1 homologues in the regulation of meristem transition and identity seems to be conserved between monocots and dicots.