Guo Z: Expression of CycD3 is transiently increased by pollination and N-(2-chloro-4-pyridyl)-N '-phenylurea in ovaries of Lagenaria leucantha

Lagenaria leucantha is an important vegetable crop and a potential model for the study of fruit develop-ment. To study the function of D cyclins in fruit development, full-length cDNA clones for two D cyclin genes were isolated from young ovaries of Lagenaria leucantha. They were classi®ed as D3 cyclins by sequence similarities and phylogenetic analysis, and nominated LlCycD3;1 and LlCycD3;2, respectively. The deduced amino acid sequence of both LlCycD3 genes contained a retinoblastoma-binding motif and a PEST-destruction motif. Unpollinated ovaries failed to develop and eventually aborted. N-(2-chloro-4-pyri-dyl)-N¢-phenylurea (CPPU) induced parthenocarpic fruit signi®cantly larger than pollinated ones. In unpollinated ovaries, the expression of both LlCycD3 genes was abundant at anthesis and then suddenly decreased, concomitant with the cessation of cell division. Pollination/fertilization induced an activation of the cell cycle accompanied by a large increase in the transcript levels of LlCycD3;1 and LlCycD3;2 in young fruits. Treating ovaries with CPPU also reacti-vated cell division and transcription of CycD3 genes and the effect was more rapid and pronounced than after pollination/fertilization