Acetyltransferase GCN5 Regulates Floral Stem Cell Activity In Arabidopsis

Histone acetyltransferases can acetylate histones and play important roles in many regulatory pathways.GCN5 encodes an important acetyltransferase in Arabidopsis thaliana.We found that GCN5 may be involved in the regulation of WUS/AG pathway,as indicated by the reduced number of floral organs and the loss of carpels in the gcn5-7 flowers.In the WUS/AG pathway,WUS,stem cell identity gene,regulates flower development by inducing the expression of AG,which specifies carpel identity.AG participates in PcG-mediated H3K27me3 removal on KNU locus,thus triggers KNU expression.KNU encodes a C2H2 zinc finger repressor and in turn represses WUS and enables the differentiation of carpels.We first verified that GCN5 can be widely expressed in flower tissues and functions in the nucleus.We also found that in gcn5-7 the acetylation level in the key regulatory region of AG decreased significantly and the expression of AG decreased in late florescence and mainly concentrated in the basal part of flower.It is suggested that GCN5 may bind to the promoter region of AG to regulate it's expression at critical timing.However,GCN5 itself does not directly bind to DNA.By screening a yeast two hybrid transcription factor library,we have identified a transcription factor PAN(AT1G68640)that may recruit GCN5 protein complex and binds to the AG promoter region.In addition,we have also checked the phenotypes of double mutants of gcn5 ag-1,gcn5 knu-2 and gcn5 wus-1.The results showed that the phenotype of knu-2 gcn5 double mutant resembles the weak phenotype of gcn5.There was no ectopic carpels in the pistil of gcn5 knu-2,which indicates that the prolonged stem cell activity in knu-2 requires the function of GCN5.