Protein Prenylation CaaX Processing in Plants

Plants have evolutionarily conserved prenyl transferases and CaaX processing enzymes. Their study has illuminated important evolutionary and mechanistic aspects relevant to the study of protein prenylation and CaaX processing. In the model plant species, Arabidopsis thaliana (Arabidopsis) mutants in the farnesyltransferase (FT), geranylgeranyltransferase-I (GGT-I) α and β subunits, and Rab geranylgeranyltransferase (RGGT) β subunit have been identified and characterized. A mutant, RNAi-silenced plants and overexpressing plant of isoprenyl carboxy methyl transferases (ICMTs) have been created and characterized. Characterization of these mutant prenyltransferases and ICMT plants has shown the important role of protein prenylation and CaaX processing during plant development and in responses to the environment, in particular to abiotic stress and light signaling. The phenotypes of the Arabidopsis prenyltransferases and ICMT mutants have prompted studies directed for their utilization for biotechnological purposes of producing agronomically superior plant species. The identification and characterization of FT and GGT-I substrates have shown that plants posses both conserved and unique prenylation substrates. More recent genome analyses have revealed that some of these protein substrates only exist in certain plant family/ies. Importantly, plants produce isoprenoids via two pathways: the cytoplasmic mevalonate (MVA) pathway and the plastidial methyl-D-erythritol-4-phosphate (MEP) pathway. This fact may have important implications to the regulatory function of protein prenylation in coordinating signaling and metabolic pathways. In the present chapter, I will cover these topics with the hope that it would be both a useful source for experts in the field of protein prenylation and for drawing more research to this understudied area of protein lipidation.