Deciding When to Flower

摘要

One of the most important developmental decisions in a plant's life is when to switch from vegetative to floral (reproductive) growth. If flowering is initiated at the wrong time of the year, it will affect the number of seeds produced and significantly reduce reproductive success. When to flower is therefore a critical decision, and consequently multiple mechanisms have evolved to align flowering with optimal environmental conditions. But how does a plant recognize the pres- ence of favorable conditions and integrate this information with its own endogenous developmental program? A new clue to this problem comes from the work of He et al. reported on page 1751 of this issue. To dissect the molecular processes that initiate flowering and trigger the change from vegetative to reproductive growth, biologists have carried out intensive genetic studies of flowering time in the model plant Arabidopsis. This has led to the discovery of many genes involved in the regulation of flowering time and the development of a number of genetic models. Despite progress in identifying the genetic pathways involved, the mechanisms by which these flowering gene products modulate the floral transition is largely unknown. He et al. now elucidate one mechanism by which plants regulate flowering time. They identify a protein called FLOWERING LOCUS D (FLD), which removes acetyl groups from (deacetylates) histone proteins in chromatin containing the FLOWERING LOCUS C (FLC) gene. The FLC protein encoded by this gene is a member of the MADS-domain family of transcription regulators and is a strong repressor of flowering. By deacetylating histones in FLC chromatin, FLD prevents transcription of FLC enabling the plant to flower.