Control of lateral meristem formation in Antirrhinum majus

Plant architecture is designed by shoot growth and branching developing from axillary meristem. Lateral meristem formation has been already studied in model plants, e.g. Arabidopsis thaliana, tomato, rice and maize (Wang and Li, 2008). The characterization of plant architecture mutants pinpointed that GRAS transcription factors LATERAL SUPPRESSOR regulate the initiation of axilary meristem (Schumacher et al., 1999; Greb et al., 2003). The Solanum lycopersicum lateral suppressor (ls) mutant and its orthologous in Arabidopsis thaliana las are unable to develop secondary meristems at the axil of leaves. Indeed, these mutants develop a single stem and do not form secondary inflorescences. In tomato ls flowers do not develop petals and are characterized by reduced female and male fertility. Also in Antirrhinum majus LAS orthologous (named ERAMOSA/ERA) greatly contributes to design plant architecture. Here we show that eramosa mutant does not develop axillary meristem, whilst the apical meristem itself is bigger. Moreover era mutant forms very few flowers completely disorganized. Preliminary results suggest also that ERA is involved in the control of ovule number since the mutant presents less ovules respect to the wildtype. Differently from its orthologous in Arabidopsis and tomato, ERA is indeed likewise expressed in the ovule primordial.