Characterization of SOC1's central role in flowering by the identification of its upstream and downstream regulators.
The transition from vegetative to reproductive development is one of the most important phase changes in the plant life cycle. This step is controlled by various environmental signals that are integrated at the molecular level by so-called floral integrators. One such floral integrator in Arabidopsis (Arabidopsis thaliana) is the MADS domain transcription factor SUPPRESSOR OF OVEREXPRESSION OF CONSTANS1 (SOC1). Despite extensive genetic studies, little is known about the transcriptional control of SOC1, and we are just starting to explore the network of genes under the direct control of SOC1 transcription factor complexes. Here, we show that several MADS domain proteins, including SOC1 heterodimers, are able to bind SOC1 regulatory sequences. Genome-wide target gene analysis by ChIP-seq confirmed the binding of SOC1 to its own locus and shows that it also binds to a plethora of flowering-time regulatory and floral homeotic genes. In turn, the encoded floral homeotic MADS domain proteins appear to bind SOC1 regulatory sequences. Subsequent in planta analyses revealed SOC1 repression by several floral homeotic MADS domain proteins, and we show that, mechanistically, this depends on the presence of the SOC1 protein. Together, our data show that SOC1 constitutes a major hub in the regulatory networks underlying floral timing and flower development and that these networks are composed of many positive and negative autoregulatory and feedback loops. The latter seems to be crucial for the generation of a robust flower-inducing signal, followed shortly after by repression of the SOC1 floral integrator.
Plant Research International, Bioscience, 6708 PB Wageningen, The Netherlands. richard.immink@wur.nl
Richard G H
RG
Immink
David
D
Posé
Silvia
S
Ferrario
Felix
F
Ott
Kerstin
K
Kaufmann
Felipe Leal
FL
Valentim
Stefan
S
de Folter
Froukje
F
van der Wal
Aalt D J
AD
van Dijk
Markus
M
Schmid
Gerco C
GC
Angenent
D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D025461:Feedback, Physiological; D035264:Flowers / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D017930:Genes, Reporter; D005816:Genetic Complementation Test / Q000379:methods; D056426:Genetic Loci; D049452:Green Fluorescent Proteins / Q000378:metabolism; D047468:Immunoprecipitation / Q000379:methods; D026161:MADS Domain Proteins / Q000235:genetics / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D012045:Regulatory Sequences, Nucleic Acid; D015398:Signal Transduction; D013997:Time Factors; D014158:Transcription, Genetic; D020798:Two-Hybrid System Techniques
C419046:AGL20 protein, Arabidopsis; D029681:Arabidopsis Proteins; D026161:MADS Domain Proteins; D049452:Green Fluorescent Proteins