Plants need to respond to their surroundings and changes in their environment. As part of those responses, plants use various hormones, which are chemically unrelated to those found in animals, to alter their growth and change metabolism. Two major types of plant hormones are the jasmonates and auxins. The presence or absence of these molecules is sensed by receptors, which if bound to the hormone trigger a pattern of biological changes in the plant. This project focuses on proteins of GH3 enzyme family that chemically modify the hormones to either promote or prevent the receptor from recognizing these molecules. The GH3 proteins attach different amino acids to the hormone, which can lead to production of an active molecule, as occurs with jasmonates, or an inactive molecule, as with the auxins. Through their biochemical activity, the GH3 proteins can control if the receptor is on or off and act as pre-receptor modulators of hormone responses in plants. Although the GH3 proteins are widespread across the plant kingdom, little is known about their biochemical function. This project aims to understand the molecular structure of the GH3 proteins by using x-ray crystallography, to investigate how the GH3 proteins catalyze their reactions on chemically diverse plant hormones, and to provide insight on the physiological roles of each GH3 protein in plant hormone responses.
Broader Impact Exploring the molecular foundations for control of plant hormone action will provide new insight on the biochemical networks involved in allocating resources for plant growth, pest defenses, and crop sustainability. For example, jasmonates are critical in altering metabolism of various compounds related to environmental changes, pest/pathogen defenses, and production of compounds useful for biofuels and industrial feedstocks. The project also focuses on training the next generation of multidisciplinary scientists. The research methods and questions used in this project cross the boundaries between biology, chemistry, and physics by integrating x-ray crystallography, biochemistry, and plant biology in both the lab and in teaching. In addition, to training graduate students a large portion of the broader impact efforts focus on undergraduate education. The PI actively recruits undergraduate students through undergraduate thesis work (Bio200, Bio500, and Chem490), the Washington U. HHMI-SURF, CD-BioRAP (an NSF-REU program), and the pre-freshman Summer Scholars in Biology and Biomedical Research program, and mentors high school students through the Pfizer-Solutia Summer Students and Teachers as Research Scientists (STARS) program. The PI is course-master for Bio4522: Protein Biochemistry Lab and has a record of developing research-oriented projects in undergraduate teaching lab courses (Jez et al., 2007 Biochem. Mol. Biol. Educ. and Arkus & Jez, 2008 Biochem. Mol. Biol. Educ.). Bio4522 is a research-oriented lab designed to have students progress through different stages of research to examine a scientific question and to work as a team. The success of the Spring 2010 & 2011 classes in generating some of the preliminary data on the Arabidopsis GH3 proteins for this proposal highlights the value of this approach for undergraduate education. During the timeframe of this proposal, each semester of the course will focus on investigating the development of GH3 protein function across evolution by examining these enzymes from different organisms in the Tree of Life.
