Synergistic action of GCN5 and CLAVATA1 in the regulation of gynoecium development in Arabidopsis thaliana.

In Arabidopsis thaliana the CLAVATA1 (CLV1) receptor and GENERAL CONTROL NON DEREPRESSIBLE 5 (GCN5) histone acetyltransferase both regulate inflorescence meristem size and affect the expression of the meristem-promoting transcription factor WUSCHEL (WUS). Single and multiple mutants of GCN5 and CLAVATA members, were analysed for their gynoecium development, using morphological, physiological, genetic and molecular approaches. The clv1-1gcn5-1 double mutants exhibited novel phenotypes including elongated gynoecia with reduced valves and enlarged stigma and style, indicating a synergistic action of CLAVATA signaling and GCN5 action in the development of the gynoecium. Reporter line and gene expression analysis showed that clv1-1gcn5-1 plants have altered auxin and cytokinin response, distribution and ectopic overexpression of WUS. WUS expression was found in the style of wild-type gynoecia stage 10-13, suggesting a possible novel role for WUS in the development of the style. CLV1 and GCN5 are regulators of apical-basal and mediolateral polarity of the Arabidopsis gynoecium. They affect gynoecium morphogenesis through the negative regulation of auxin biosynthesis and promotion of polar auxin transport. They also promote cytokinin signaling in the carpel margin meristem and negatively regulate it at the stigma. Finally, they synergistically suppress WUS at the centre of the gynoecium.