Flower development pathways

Miguel A. Blzquez 0 0 Instituto de Biologia Molecular y Celular de Plantas (CSIC), Universidad Politecnica de Valencia , Camino de Vera s/n, 46022 Valencia , Spain This diagram displays our current knowledge of the signaling pathways that promote flowering and of how floral architecture is determined in Arabidopsis. The model is based mainly on genetic interactions between mutants affected in flowering time, floral meristem identity and floral organ identity. Some interactions, such as the activation of the transcription of floral organ identity genes by LEAFY, have also been confirmed at the molecular level. - Light is perceived by photoreceptors and, if the circadian clock identifies long photoperiods, activates a facultative long-day pathway (shown in red). If the photoperiod is short, flowering depends exclusively on a gibberellin-dependent pathway (shown in yellow) and on a photoperiod-independent pathway that is primarily responsive to temperature (shown in blue). The metabolic state of the plant is reflected in the amount of circulating sucrose (shown in pink), which also promotes flowering. The ultimate targets for the flowering-time pathways are the floral meristem identity genes (shown in green), whose activity confers floral identity to newly emerging primordia. The correct arrangement of floral organs is established initially by the floral organ identity genes, whose regionalized expression is a consequence of activation by floral meristem identity proteins and mutual interactions (shown in brown). REFERENCES Shoot elongation Cell Science at a Glance on the Web Electronic copies of the full-size poster insert are available in the online version of this article (see www.biologists.com/jcs). Files in several formats are provided and may be downloaded for use as slides. (...truncated)