Combinatorial Activity of Short Vegetative Phase and Flowering Locus C in the Repression of Flowering Time

MATEOS, J. L.; MADRIGAL, P; TSUDA, K; COUPLAND, G

Providence

Conferencia; Plant Biology 2013; 2013

American Society of Plant Biology

The transition to flowering is controlled by a regulatory network that responds both to developmental cues and environmental signals perceived by plants. This developmental change is driven by precise patterns of gene expression, which are regulated by transcription factors (TFs) converging on cis-regulatory elements. TFs FLOWERING LOCUS C (FLC) and SHORT VEGETATIVE PHASE (SVP) are two of the major flowering time repressors which act by blocking transcription of the floral pathway integrators in the annual specie Arabidopsis thaliana. FLC and SVP belong to the family of MADS-box TFs and were shown to form a complex in vivo. Mutations on either of both genes lead to similar developmental defects, yet the molecular mechanism underlying this shared phenotype is not understood.  We addressed the regulatory input of these two essential transcription factors alone and as a complex by analyzing the direct and indirect targets at a genome-wide level through ChIP-seq and expression analysis in high order mutants. Contribution of single component is described and evidence that the complex acts predominantly via functional redundancy controlling the transcriptional network is provided. However, among the gene network we found a subgroup of genes which exclusively depend on the interaction of these two proteins. Additionally, the combined role of FLC and SVP on a subset of genes are integrated in a repressive manner. Genome-wide identification of SVP occupancy reveals its involvement in the control of flowering throughout different pathways. Interestingly, we show that the binding scenario of SVP is strongly affected by the presence of its partner FLC both at a quantitative as well as a qualitative level strengthening the role of the complex. More generally, this study not only gives a global view of the regulatory input of both factors during development but also shows considerable flexibility in the regulatory output of two factors, leading to additive, cooperative, and repressive modes of co-regulation.