Abstract
Plant forms display a wide variety of architectures, depending on the number of lateral branches, internode elongation and phyllotaxy. These are in turn determined by the number, the position and the fate of the Axillary Meristems (AMs). Mutants that affect AM determination during the vegetative phase have been isolated in several model plants. Among these genes, the GRAS transcription factor LATERAL SUPPRESSOR (Ls) plays a pivotal role in AM determination during the vegetative phase. Hereby we characterize the phylogenetic orthologue of Ls in Antirrhinum, ERAMOSA (ERA). Our data supported ERA control of AM formation during both the vegetative and the reproductive phase in snapdragon. A phylogenetic analysis combined with an analysis of the synteny of Ls in several species strongly supported the hypothesis that ERA is a phylogenetic orthologue of Ls, although it plays a broader role. During the reproductive phase ERA promotes the establishment of the stem niche at the bract axis but, after the reproductive transition, it is antagonized by the MADS box transcription factor SQUAMOSA (SQUA). Surprisingly double mutant era squa plants display a squa phenotype developing axillary meristems, which can eventually turn into inflorescences or flowers.
Highlights
Plant forms display a wide variety of architectures, depending on the number of lateral branches, internode elongation and phyllotaxy
During the early vegetative phase, the leaves develop according a decussate phyllotaxy and Axillary Meristem (AM) are formed at the leaf axis[11]
The reproductive phase is marked by a switch to a spiral phyllotaxy, during which single bracts develop at each node and subtend a new floral AM (Fig. 1a–d)[11]
Summary
Plant forms display a wide variety of architectures, depending on the number of lateral branches, internode elongation and phyllotaxy. The Arabidopsis las plants do not develop lateral branches during vegetative growth, but inflorescences and flowers appear normal. Era plants are unable to produce AMs during the vegetative phase, whilst during the reproductive phase, era inflorescences develop very few flowers.
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