The Cardinal Edge


Protein prenylation, a common lipid post-translational modification, is required for growth and development in eukaryotes. One type, , but its biological function is not well known. The moss Physcomitrella patens (P. patens) was used as a model organism due to its simple structure, limited cell types, sequenced genome, and its high gene targeting efficiency. P. patens has one copy of Rab-GGT α subunit (PpRGTA1) and two copies of β subunit (PpRGTB1 and PpRGTB2). It has been found that the knockout of either PpRGTB1 or PpRGTB2 results in no visible phenotype, which indicates that these genes must be functionally redundant. The knockout of both PpRGTB1 and PpRGTB2 genes has shown to be lethal, which means Rab-GGT is required for viability. To determine the function of Rab-GGT, we used the RNA interference approach to down-regulate the expression level of PpRGTB2 in the PpRGTB1 knockout background to observe these phenotypic changes. P. patens grows in long thread-like filaments made of cells, also called protonema. Protonema includes two different cell types, chloronema and caulonema. Each of these cell types has distinct features that can be observed and quantified. This study focuses on quantifying P. patens’ distinctive features in cell size, width, and the amount of protruding caulonema present in the wildtype vs PpRGTB2 knockdown lines. The observed defects indicate the RGTB2 gene plays a vital role in moss growth and development.