This project is aimed toward the examination, composition and function of the flagellar transition region of Chlamydomonas reinhardtii. The combined genetic, molecular, and ultrastructural approach will focus on the presence of the calcium-binding protein centrin, which is thought to be in the stellate fibers of the transition region. Several centrin mutants have been characterized, including one where glu 101 has been converted to lys in one of the E-F-hands (a calcium binding site on the protein. Chlamydomonas mutants should also permit the enrichment of flagellar transition regions, where the phenotypic expression of supernumarary transition regions increases the likelihood of biochemical purification protocols. It is unlikely that the transition region can be studied in this fashion with any other organism. %%% All eukaryotic cilia and flagella possess a highly specialized transition region in the section of the axoneme that is immediately adjacent with the cell body. The transition region is not well understood functionally, though it has been characterized ultrastructurally in a number of organisms. In the unicellular alga Chlamydomonas reinhartii, the flagellar transition region can be studied by a combination of methods that include genetic manipulation, biochemical isolation and ultrastructural observation. This project combines these approaches in a novel way that should contribute important compositional and functional information about the flagellar transition region, not only in C. reinhardtii, but in other flagellated cells, as well.
