Article

SWI2/SNF2 chromatin remodeling ATPases overcome polycomb repression and control floral organ identity with the LEAFY and SEPALLATA3 transcription factors.

Department of Biology, University of Pennsylvania, Philadelphia, PA 19104, USA.
Proceedings of the National Academy of Sciences (impact factor: 9.68). 02/2012; 109(9):3576-81. DOI:10.1073/pnas.1113409109 pp.3576-81
Source: PubMed

ABSTRACT Patterning of the floral organs is exquisitely controlled and executed by four classes of homeotic regulators. Among these, the class B and class C floral homeotic regulators are of central importance as they specify the male and female reproductive organs. Inappropriate induction of the class B gene APETALA3 (AP3) and the class C gene AGAMOUS (AG) causes reduced reproductive fitness and is prevented by polycomb repression. At the onset of flower patterning, polycomb repression needs to be overcome to allow induction of AP3 and AG and formation of the reproductive organs. We show that the SWI2/SNF2 chromatin-remodeling ATPases SPLAYED (SYD) and BRAHMA (BRM) are redundantly required for flower patterning and for the activation of AP3 and AG. The SWI2/SNF2 ATPases are recruited to the regulatory regions of AP3 and AG during flower development and physically interact with two direct transcriptional activators of class B and class C gene expression, LEAFY (LFY) and SEPALLATA3 (SEP3). SYD and LFY association with the AP3 and AG regulatory loci peaks at the same time during flower patterning, and SYD binding to these loci is compromised in lfy and lfy sep3 mutants. This suggests a mechanism for SWI2/SNF2 ATPase recruitment to these loci at the right stage and in the correct cells. SYD and BRM act as trithorax proteins, and the requirement for SYD and BRM in flower patterning can be overcome by partial loss of polycomb activity in curly leaf (clf) mutants, implicating the SWI2/SNF2 chromatin remodelers in reversal of polycomb repression.

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Keywords

AG regulatory loci peaks
 
central importance
 
class C gene AGAMOUS
 
correct cells
 
curly leaf
 
direct transcriptional activators
 
female reproductive organs
 
floral organs
 
Inappropriate induction
 
LFY association
 
lfy sep3 mutants
 
partial loss
 
polycomb repression
 
reproductive fitness
 
reproductive organs
 
SWI2/SNF2 ATPase recruitment
 
SWI2/SNF2 ATPases
 
SWI2/SNF2 chromatin remodelers
 
SWI2/SNF2 chromatin-remodeling ATPases SPLAYED
 
SYD binding