The long-term goals of my research are to understand the cellular and molecular properties of cilia/flagella that underlie their functions. In addition to being used for motility, these organelles are widely employed as sensors to communicate environmental and physiological cues to the cell. My laboratory uses the biflagellated green alga Chlamydomonas reinhardtii as a model system to study flagella. We are investigating two sensory/signaling pathways focused on these microtubule-filled organelles. One pathway, the regulated flagellar disassembly pathway, brings about flagellar disassembly when cells sense environmental conditions inappropriate for the presence of flagella. The second, the flagellar adhesion induced signaling pathway, activates gametes when they sense (by flagellar adhesion) the presence of a gamete of the opposite sex. We have discovered that a Chlamydomonas member of the aurora protein kinase family, CALK, is an essential effector in the flagellar disassembly pathway. We propose experiments to learn more about the role of CALK in regulated flagellar disassembly, including testing the idea that CALK directly or indirectly regulates intraflagellar transport. In the flagellar adhesion-induced signaling pathway we determined that a protein tyrosine kinase in flagella is activated by flagellar adhesion and that its substrate is a cGMP-dependent protein kinase. Moreover, we found that activation and functioning of the flagellar adhesion-induced pathway are critically dependent on intraflagellar transport. We propose experiments to learn more about the early steps in flagellar adhesion-induced signaling and the role of intraflagellar transport in the pathway. ? ?
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