Calendar Name: seminars Scheduled for: Monday, September 6 2010, 11:00 - 12:30 Event text: Prof Maria Helena S. Goldman Department of Biology, FFCLRP, University of S�o Paulo BRAZIL Details: "SCI1, A TISSUE-SPECIFIC CELL CYCLE REGULATOR THAT CONTROLS STIGMA/STYLE DEVELOPMENT" ABSTRACT The success of plant reproduction depends on the appropriate development of the reproductive organs, which involves general and specific regulatory networks. We have characterized a gene, SCI1 (stigma/style cell cycle inhibitor 1), encoding a nuclear small lysine-rich protein that exerts an inhibitory action on cell cycle. qRT-PCR and in situ hybridization experiments showed that SCI1 is stigma/style-specific and developmentally regulated. SCI1 RNAi knockdown and overexpression transgenic plants exhibited stigmas/styles with remarkably enlarged and reduced areas, respectively, due to differences in cell numbers. Alterations on SCI1 expression affected cell divisions on the stigmatic secretory zone (SSZ) and the differentiation timing of the papillar cells. Taken together, our results reveal that SCI1 is a novel tissue-specific negative cell cycle regulator that couples stigma cell division and differentiation. Additionally, two-hybrid and BiFC experiments showed that SCI1 interacts with A-type cyclins. We conclude that SCI1 represents a novel developmentally regulated tissue-specific gene that controls cell proliferation/differentiation, probably as a component of a signaling pathway involved in upper pistil development.