NANOMETER-SCALE VIBRATION IN MUTANT AXONEMES OF CHLAMYDOMONAS

Flagellar axonemes of sea urchin sperm display high frequency (200-400 Hz) vibration with nanometer scale amplitudes in the presence of ATP [Kamimura and Kamiya, 1992: J. Cell Biol. 116:1443 -1454]. To investig ate how various axonemal components affect the vibration, we examined vibration in wild-type and mutant axonemes of Chlamydomonas. At 1 mM A TP, wild-type axonemes underwent vibration at 100-650 Hz with amplitud es of 4-40 nm. This vibration was similar to, but less regular than, t hat in sea urchin sperm. Axonemes of the mutants ida1 and ida4 lacking part of the inner arm dynein underwent vibrations indistinguishable f rom that of wild-type. The mutant oda 1 lacking the entire outer arm u nderwent vibration at about half the wild-type frequency. Unexpectedly , the paralyzed mutants pf18 lacking the central pair and pf14 lacking the radial spokes displayed vibration with significantly higher frequ encies and smaller amplitudes than those in the wild-type vibration. T hese results indicate that the high-frequency vibration is common to m any kinds of mutant axonemes that lack various axonemal substructures, but that its manner is sensitive to the presence of outer arm dynein and the central pair/radial spoke system. Simultaneous measurements of amplitude and frequency in wild-type and mutant axonemes suggest that the velocity of microtubule sliding in vibrating axonemes is lower th an the velocity of sliding under load-free conditions. The velocity is particularly low in pf18. A possible mechanism is proposed to explain the lower sliding velocity and vibration amplitude in the pf18 axonem e, based on an assumption that central pair/radial spoke system may wo rk to regulate the switching of two antagonizing forces within the axo neme. (C) 1994 Wiley-Liss, Inc.