Flagellar coordination in Chlamydomonas cells held on micropipettes

The two flagella of Chlamydomonas are known to beat synchronously: During b reaststroke beating they are generally coordinated in a bilateral way while in shock responses during undulatory beating coordination is mostly parall el [Ruffer and Nultsch, 1995: Botanica Acta 108:169-276]. Analysis of a gre at number of shock responses revealed that in undulatory beats also periods of bilateral coordination are found and that the coordination type may cha nge several times during a shock response, without concomitant changes of t he beat envelope and the beat period. In normal wt cells no coordination ch anges are found during breaststroke beating, but only short temporary async hronies: During 2 or 3 normal beats of the cis flagellum, the trans flagell um performs 3 or 4 flat beats with a reduced beat envelope and a smaller be at period, resulting in one additional trans beat. Long periods with flat b eats of the same shape and beat period are found in both flagella of the no n-phototactic mutant ptx1 and in defective wt 622E cells. During these peri ods, the coordination is parallel, the two flagella beat alternately. A cor relation between normal asynchronous trans beats and the parallel-coordinat ed beats in the presumably cis defective cells and also the undulatory beat s is discussed. In the cis defective cells, a perpetual spontaneous change between parallel beats with small beat periods (higher beat frequency) and bilateral beats with greater beat periods (lower beat frequency) are observ ed and render questionable the existence of two different intrinsic beat fr equencies of the two flagella cis and trans. Asynchronies occur spontaneous ly but may also be induced by light changes, either step-up or step-down, b ut not by both stimuli in turn as breaststroke flagellar photoresponses (BF PRs). Asynchronies are not involved in phototaxis. They are independent of the BFPRs, which are supposed to be the basis of phototaxis. Both types of coordination must be assumed to be regulated internally, involving calcium- sensitive basal-body associated fibrous structures. (C) 1998 Wiley-Liss, In c.