CA2-DEPENDENT WAVE-FORM CONVERSION IN THE FLAGELLAR AXONEME OF CHLAMYDOMONAS MUTANTS LACKING THE CENTRAL-PAIR RADIAL SPOKE SYSTEM()

Chlamydomonas flagella undergo a striking waveform conversion from an asymmetrical ciliary type to a symmetrical flagellar type when the cel l is stimulated by intense light and the Ca2+ concentration within the flagellum is increased above similar to 10(-6) M. To see whether the central-pair/radial spoke system is needed for this conversion as sugg ested by previous studies, we examined the effect of Ca2+ on the react ivated axonemes of the mutants lacking the central pair (pf18) or the radial spokes (pf14). Although the flagella of these mutants are paral yzed in vivo, demembranated axonemes can be reactivated to beat under certain nucleotide conditions such as in the presence of low concentra tions (<100 mu M) of ATP. We examined the waveform of the axonemes rea ctivated at 20 mu M ATP in the presence of 10(-8)-10(-4) M Ca2+ and fo und that these axonemes, as well as the wild-type axonemes, undergo a waveform conversion over a Ca2+ concentration range of 10(-7)-10(-5) M : a highly asymmetrical waveform at <10(-6) M Ca2+ and a symmetrical w aveform at >=10(-5) M Ca2+. Although the waveform is different between the mutants and the wild type, the Ca2+ concentration at which the wa veform conversion occurred was similar. These results indicate that th e central pair/radial spoke system is not essential for the waveform c onversion. (C) 1997 Wiley-Liss, Inc.