Intellectual merit: Phytobilins are pigments that perform significant light harvesting roles in oxygenic photosynthetic organisms from unicellular algae to green plants. When attached to proteins (biliproteins), phytobilins harvest light energy to drive photosynthesis in blue-green, red and brown algae, and trigger adaptive signaling pathways vital to survival in a constantly fluctuating light environment. This project focuses on ferredoxin-dependent bilin reductases (FDBRs), a family of metal-free radical enzymes that are responsible for the synthesis of phytobilin pigment precursors of both classes of light sensor proteins. Using a variety of biochemical and biophysical techniques, this research seeks to elucidate FDBR function at the molecular level via a combination of x-ray crystallography, molecular biology and biochemical analysis. Such knowledge is needed for development of activators/inhibitors of FDBRs that can be used to enhance light perception, growth and development of oxygen-evolving photosynthetic organisms upon which all life on earth depends. These studies also seek to understand the biological role of a unique FDBR gene in the green alga Chlamydomonas reinhardtii, an oxygenic photosynthetic organism that lacks all known light sensing biliproteins. Using genetic, genomic and phenotypic analyses of this organism, several hypotheses for the function of this gene will be assessed. It is anticipated that such studies will lead to insight into new functions of bilin metabolism hitherto unrecognized. Since Chlamydomonas retains features common to plants and animals, this research is expected not only to yield new avenues to improve crop productivity, but could reveal novel bilin-dependent regulatory pathways of relevance to human/animal physiology and disease.
The broader impact of this research project will integrate research and education by training scientists at all levels (postdocs, graduate, undergraduate and high school students) in the methods of molecular biology, enzymology, protein chemistry, structural biology, computational biology and reverse genetics. Undergraduates (including an underrepresented minority student) will conduct a number of aspects of this research. Additionally, to broaden participation of underrepresented groups and pto romote teaching, the labs participate in a number of development and minority-training programs, including: MURPPS (Minority Undergraduate Research Participation in the Physical Sciences), SURPRISE (Summer Undergraduate Research Program In Science and Engineering), BUSP (Biology Undergraduate Scholars Program), and in high school programs including Young Scholar Program, SEED (Success in Engineering through Excellence and Diversity Program), and Davis high school advanced biotechnology class.
This project is being supported by the Biomolecular Systems cluster in MCB and the Inorganic, Bioinorganic, and Organometallic Chemistry program in CHE.
Life on our planet depends on the success of plants, algae and phytoplanckton in the oceans to convert light energy into chemical energy. Light energy that comes from the sun fluctuates on a daily basis due to the rotation of the earth. The duration of sunlight also depends upon the earth's tilt that leads to seasonal changes in the daylength. Thus, all photosynthetic species must maximize light capture at dawn and at twilight when light is limiting, and must avoid absorbing too much light when light is bright at midday. The pigments responsible for 'sensing' the light energy and daylight are linear tetrapyrroles, blue-colored natural products that come from heme, the red-colored oxygen carrier in our blood. Our research addresses how these pigments are made, and how the enzymes responsible for their production are regulated in plants and algae. Our studies involve taking x-ray snapshots of these catalysts that are too small to see with the naked eye. By making changes to individual amino acids within these protein catalysts and taking x-ray images, we seek to understand how these nano-machines work at the molecular level. Our studies have identified key components of these machines that control their efficiency and the structure of their pigment products. Companion studies focus on the role of these catalysts in green algae, which have lost the capacity to sense the light since they are missing the pigment-binding proteins needed to support their vision. Through these studies, we have discovered a new role for these pigments as signaling molecules that function to protect alga from damage at dawn when the sun rises. While not yet understood, this sensing system is likely to function in many species that live and eat photosynthetic organisms in their environment, providing an adaptive advantage to entrain their metabolism and behavior to the daily light cycle. Other impacts of this research project include education and training of future scientists. This grant was able to support either directly or indirectly the training of Postdoctoral scholars, graduate students, undergraduate students (including under representative minorities), and high school students. All of the trained researchers have advanced to the next level of their scientific career in part from this grant.
