Post-translational phosphorylation dynamics in Arabidopsis and Physcomitrella

Abstract

Phosphorylation is the most abundant post-translational modification that involves the chemical addition of a phosphate group onto serine, threonine, or tyrosine residues of substrate proteins. Phosphorylation is utilized to regulate protein activity, stability, or localization to respond to cellular needs. This dissertation starts in Chapter Two by discussing the phospho-regulation of the Arabidopsis plant cellulose synthase complex and cellulose synthase-like proteins. Chapter Three discusses protein-protein complex dynamics in the model moss plant Physcomitrella patens. This chapter demonstrates that Physcomitrella convergently evolved to contain hetero-oligomeric cellulose synthase complexes similar to land plants like Arabidopsis. Chapter Four investigates how the loss-of-function of a secretory pathway protein can suppress the near-sterile phenotype of a calcium-dependent protein kinase in Arabidopsis pollen, providing the first genetic connection between a calcium kinase and the secretory pathway. Lastly, Chapter Five utilizes quantitative phospho-proteomics to identify two proteins with heat-stress-dependent phosphorylation sites with implications on pollen fitness. To conclude, this dissertation describes a phosphorylation-dependent link between the topics covered in each chapter and a concluding perspective on how this work could contribute to the future of plant phosphorylation research