XVI International Botanical Congess

Protein prynylation involves the covalent attachment of either teh 15 or 20-carbon isoprenes farnesylpyrophosphate (FPP) or geranylgeranylpyrophosphate (GGPP), respectively, to conserved cysteine residues located near or at the carboxy terminal end of several proteins. Prenylation is believed to promote membrane attachment and regulation of protein-protein interactions. To gain more insight into the function of protein prenylation in plants we searched the protein data base for plant protein, which are potentially prenylated and characterized the role of prenylation in their function. Two of the proteins we identified are the Arabidopsis floral transcription factor APETALA1 (AAP1), which is preferentially farnesylated, and CaM53, a Ca2+ Calomodulin from Petunia, which is preferentially geranylgeranylated. The subcellular localization of both AP1 and CaM53 is dependent upon their prenylation status. Both prenylated and non-prenylated forms of AP1 are localized in th enucleus but the non-prenylated mutant form accumulates in the nucleolus whereas the wild type protein remains dispersed through the nuclear matrix. The prenylated CaM53 is localized in the plasma membrane and the non-prenylated mutant accumulates in the nucleus. Moreover, inhibition of mevalonate (the precursor molecule for FPP and GGPP) biosynthesis resulted in the accumulation of AAP1 in the nucleolus and CaM53 in the nucleus. Experiments with transgenic plants show that enhanced nuclear localization of CaM53 can be coupled to changes in the metabolic status of the cells. These results suggest that protein prenylation had evolved as a mechanism, which coordinates between the metabolic and signaling pathways.