This research uses the model organism Chlamydomonas reinhardtii to understand how complex molecular structures are assembled at specific locations within a cell. Chlamydomonas is a single-celled, photosynthetic alga found in freshwater habitats throughout the world. Chlamydomonas cells optimize photosynthesis by swimming toward or away from light using two flagella (the mother flagellum and the daughter flagellum) at the anterior end of the cell. Light intensity and direction are sensed by the eyespot, a complex structure that is always found at the outer edge of the cell, half way between the anterior and posterior ends of the cell, on the same side of the cell as the daughter flagellum. The eyespot contains photoreceptor proteins that are similar to the rhodopsins in mammalian eyes, and a variety of other proteins that are located in the cell membrane layers or lipid granules that are unique to the eyespot. This research will test the hypothesis that the photoreceptor proteins are required for the assembly and/or placement of the eyespot, and will identify and characterize other proteins involved in eyespot formation. A molecular model of eyespot assembly resulting from this research will be applicable to studies of a wide variety of other sub-cellular structures in other biological systems.
BROADER IMPACTS Chlamydomonas has long been a model organism for the study of photosynthesis and flagellar assembly, so the conditions for growth, genetic manipulation, and molecular characterization of this photosynthetic alga are well established. Studying the Chlamydomonas eyespot is, therefore, an excellent model system for training the diverse group of young scientists pursuing degrees at the University of Arizona. A number of undergraduate and graduate students have completed their senior, honor, or Ph. D. theses studying eyespot assembly, and University of Arizona students continue to pursue eyespot-related research. Additionally, established relationships with two small college professors and their students will continue. Because the grass-green Chlamydomonas cell with its bright orange eyespot and long flagella is easily viewed through the light microscope, visiting the laboratory has also been popular with grade school students. In response, the researchers have developed Chlamydomonas-based biology lessons that will be presented to K-12 students in their classrooms. Chlamydomonas is only one of a very large number of photosynthetic microorganisms that respond to light. Student interest in Chlamydomonas is increasing as these microorganisms become the focus of efforts to produce food and fuel using energy from the sun.
