Brooke Rodwell graduated in 2014 from the University of Michigan-Dearborn with her Bachelor of Science Degree in Biology. That same year she joined the Biological Sciences Department at Wayne State University as a Ph.D. Student and Graduate Teaching Assistant. After one semester she joined the lab of Dr. Penelope Higgs and began working on her own research project. Brooke’s project involves understanding how eukaryotic-like protein kinases control core processes necessary for the multicellular life cycle of the bacterium Myxococcus xanthus. Upon completion of her degree, Brooke plans to obtain a career in industry.
Two eukaryotic-like protein kinases, Pkn8 and Pkn14,
control sporulation in the bacterium, Myxococcus xanthus
Myxococcus xanthus is an excellent model system for multicellular behavior in bacteria. Under nutrient limitation, the cells enter a developmental program in which cells segregate into at least three distinct fates: fruiting bodies filled with spores, programmed cell death, or formation of a persister-like state. Our group uses M. xanthus as a model system to understand how signaling systems have evolved to coordinate multicellular behavior and cell fate segregation. Cell fate segregation involves the transcriptional regulator, MrpC, which is a member of the Crp/Fnr transcriptional regulator family. No ligand for this protein has been identified; instead MrpC appears to be regulated by phosphorylation via two eukaryotic-like protein kinases, Pkn8 and Pkn14. To understand how phosphorylation regulates MrpC, we are characterizing the role of these kinases using a combination of genetic and biochemical analyses. We have demonstrated Pkn14, but not a kinase-inactive mutant (Pkn14K48N), autophosphorylates in vitro and phosphorylates MrpC. Phosphorylation is not observed if a putative TTSS phosphorylation motif in MrpC is mutated to AAAA. This MrpC mutant also fails to sporulate, suggesting that phosphorylation is necessary to direct MrpC to induce the sporulation pathway. While strains producing kinase inactive Pkn8 (Pkn8K116N) or Pkn14 (Pkn14K48N) form wild type levels of spores, pkn8K116N pkn14K48N double mutants produce 35% of wild type spores. These results suggest that Pkn8 and Pkn14 act redundantly to phosphorylate MrpC. We are currently investigating whether Pkn8 also phosphorylates MrpC directly, and are examining which of these residues in the TTSS motif are phosphorylated by Pkn8 and/or Pkn14.