Chemotaxis in the Green Flagellate Alga Chlamydomonas

Behavior of the green flagellate alga Chlamydomonas changes in response to a number of chemical stimuli. Specific sensitivity of the cells to different substances might appear only at certain stages of the life cycle. The heterogamous species C. allensworthii demonstrates chemotaxis of male gametes towards pheromones excreted by female gametes. In C. reinhardtii chemotaxis towards tryptone occurs only in gametes, whereas chemotaxis towards ammonium, on the contrary, only in vegetative cells. Chemotaxis to different chemical stimuli might involve different mechanisms of reception and signal transduction, elucidation of which has only recently begun. Indirect evidences show that the cells likely respond to tryptone with changes in the membrane electrical conductance. The recently completed project of sequencing the whole nuclear genome of C. reinhardtii provides the basis for future identification of molecular elements of the chemosensory cascade in this alga.