Phosphatase Regulation of Heterotrimeric G protein Signaling in Arabidopsis Thaliana

In the Arabidopsis thaliana heterotrimeric G protein signaling pathway, the phosphorylation of REGULATOR OF G PROTEIN SIGNALING (RGS1), leads to its internalization and subsequent activation of the G protein at the plasma membrane. A subset of kinases that phosphorylates this protein has been identified, so it is expected that an associated phosphatase(s) exists to act in the opposite direction. Phosphatases may reverse RGS1 phosphorylation and endocytosis, resulting in RGS1 returning to the membrane and regulating the G protein. Five candidate phosphatases have been identified in a G protein interactome as potential interactors with RGS1. After genotyping t-DNA insertion alleles of the phosphatases to identify homozygous knockouts, an etiolated hypocotyl assay was performed as a way to compare G protein signaling activation of phosphatase mutants to wild type and an RGS1 mutant, rgs1-2. Quantitative PCR was used to compare expression levels of phosphatase genes in mutants and wild type. The phosphatase mutants showed a similar elongated hypocotyl phenotype to rgs1-2 plants, indicating upregulated G protein signaling activity in both cases. These phosphatases likely function to downregulate the G protein signaling pathway possibly by removing phosphates from RGS1. These findings hold implications in understanding and manipulating hypocotyl elongation in Arabidopsis by giving insight into the molecular mechanisms that control phosphorylation of RGS1 and activation of G protein signaling.Bachelor of Scienc