9604681 Yang Protein farnesyltransferase (FTase)-mediated attachment of a lipid (i.e., farnesyl) moiety to proteins facilitates translocation to the plasma membrane and thus activation of signaling proteins such as p21ras. As a result, FTase plays an important role in many signaling pathways. Recent studies suggest that FTase plays a critical role in abscisic acid signaling and cell cycle control in plants. However, farnesylated proteins involved in these plant signaling events have not been identified. In our preliminary studies, an Arabidopsis Ras-like small GTP-binding protein (RLP1) was shown to be farnesylated in vitro, and its full-length cDNA was sequenced. This represents the first plant signaling protein known to be farnesylated and provides a strong candidate for a farnesylated protein in ABA signaling or cell cycle control. In this revised objective, we will investigate the function of this G-protein in plants. Two specific experiments will be conducted. 1) RLP1 will be fused to the jellyfish green fluorescence protein and expressed in tobacco BY-2 cells to demonstrate in vivo farnesylation of RLP1 and to determine its subcellular localization. 2) Dominant negative and constitutively active mutant forms of RLP1 will be created by site-directed mutagenesis and expressed in BY-2 cells to directly assess its role in plant signaling pathways such as ABA or mitogenic signaling. This work will provide significant new insight into the role of farnesylation and farnesylated proteins in signal transduction. This project will examine the a signal processes that are involved in regulating cell division in plant cells. Understanding how plant cell division is regulated is an important fundamental process with implications in biotechnology and agriculture. Dr. Yang has discovered that one protein that may be involved in signaling during cell division is modified with the attachment of a lipid. The attachment and removal of the lipid may be one of the essential steps in the signali ng process. This project will provide detailed information on the correlation between lipid modification of the protein and the regulation of plant cell division.
