melon fruit shape

Shapes of vegetables and fruits are the result of adaptive evolution and human selection. Cellular modules controlling cell shape has been identified. However, little is known on signals coordinating organ development and shape. Here we describe the characterization of a melon mutation rf1, leading to round fruit. Using positional cloning, we identified the causal gene as the monoecy sex determination gene CmACS7, and survey of melon germplasms showed strong association between fruit shape and sexual types. We show that CmACS7-mediated ethylene production in carpel primordia enhances cell expansion and represses cell division, leading to elongated fruit. Spatio-temporal gene expression analysis revealed the role of ethylene in the recruitment of two regulatory modules. The first implicates E2F-DP transcription factors, controlling cell elongation versus cell division. The second implicates OVATE and TRM5-related proteins, controlling cell division patterns. Altogether, we reveal dual role of ethylene in sex determination and ovary and fruit shape.