CLV1 interacts with UFO in modulation of gynoecium development in Arabidopsis thaliana

The gynoecium is the female reproductive structure in flowering plants. It has been known that the CLAVATA1 (CLV1) gene regulates the floral meristem maintenance and floral organ number in Arabidopsis thaliana. However, whether CLV1 plays roles in gynoecium development remains uncharacterized. In this study, we showed that CLV1 genetically interacts with Unusual Floral Organs (UFO) to regulate the development of Arabidopsis gynoecium. Through forward genetic screen, we identified a clv1 allele, clv1-9, showing abnormal gynoecium development. Some epidermal cells on the growing inner surfaces of the clv1-9 gynoecium failed to fuse after contacting with each other, suggesting that CLV1 is essential for proper postgenital fusion. Furthermore, the ufo clv1-9 double mutant exhibited an expanded upper gynoecium, narrowed lower part of the ovary, altered vascular patterning and abaxial outward proliferation of the transmitting tract tissues. The transcription level of the ETT gene, which is required for gynoecium structure and pattern formation, was down-regulated in the ufo clv1-9 double mutant genoecia. Taken together, our results indicate that CLV1 functions together with UFO to regulate gynoecium development likely through modulating the expression of ETT.