Non-inductive conditions expose the cryptic bract of flower phytomeres in Arabidopsis thaliana

The aerial plant architecture is built by phytomeres which are metameric units, each composed of a stem segment (internode) and a leaf with axillary meristem (node). In Arabidopsis thaliana, fully developed flower phytomeres lack the leaf even if they temporarily exhibit a cryptic bract (CB) during early development. Recently, we demonstrated that the CB becomes more prominent under non-inductive short-day conditions. However, a full outgrowth as cauline leaf is prevented by Polycomb-group (Pc-G) proteins which silence the MADS gene FLOWERING LOCUS C (FLC) encoding a repressor of FLOWERING LOCUS T (FT). Also the loss of SHORT VEGETATIVE PHASE (SVP) supresses ectopic leaves at the base of Pc-G deficient pedicels. Here we present new expression data of flowering genes LEAFY (LFY) and TWIN SISTER OF FT (TSF) and the re-analysis of morphological changes in Pc-G deficient plants suggesting that the specifications of CB and floral meristem (FM) are separated in time.