Prenylation in the Moss Physcomitrella patens

Protein prenylation is a post-translational modification that involves the addition of lipid groups to the end of a target protein and is necessary for protein activity. Prenylation has important roles in the cell: targeting and localizing proteins to subcellular compartments and promoting protein-protein interactions. Recently, we have found Protein Prenyltransferase Alpha Subunit-like (PPAL), which shares structural similarities to known prenylation enzymes. However, the biochemical function of PPAL is still unknown. PPAL is present in a single copy in other plants examined to date but is present in two copies in moss. Knockouts in our lab of either PpPAL1 or PpPAL2 in moss P. patens has proven to be lethal, suggesting that PPAL1 and PPAL2 are essential for survival. Our past study using plant Arabidopsis revealed that PPAL is required for sugar metabolism and development. This study was designed to expand our preliminary study across plants and explore the role that PPAL1 and PPAL2 play in growth, development, and sugar metabolism in moss P. patens. Gene knock-down approaches was used to reduce the function of PpPPAL1 and PpPPAL2 for in-depth phenotypic studies. By synthesizing an inducible artificial microRNA and growing the PpPPAL1 and PpPPAL2 amiRNA moss transformant in DMSO/BETA-estradiol medium, we reduced the expression levels of PpPPAL1 and PpPPAL2. Phenotypic changes were examined under the microscope and the results showed that PpPPAL1 and PpPPAL2 knockdowns had fewer gametophores and fewer caulonema, structures that are required for reproduction and polar cell elongation respectively. Ultimately, our data reveals PpPPAL1 and PpPPAL2 knockdowns exhibit reduced growth and propagation, although knockdown lines are still viable, suggesting that further exploration of metabolic processes is needed. Studying PPAL1 and PPAL2 can provide us more information as to conserved prenylation mechanisms and their function, which in turn has applications to biofuels and developmental diseases