A Chlamydomonas outer arm dynein mutant missing the α heavy chain

Abstract

A novel Chlamydomonas flagellar mutant (oda-11) missing the a heavy chain of outer arm dynein but retaining the β and γ heavy chains was isolated. Restriction fragment length polymorphism analysis with an α heavy chain locus genomic probe indicated that the oda-11 mutation was genetically linked with the structural gene of the a heavy chain. In crosssection electron micrographs, the oda-11 axoneme lacked the outermost appendage of the outer arm, indicating that the α heavy chain should be located in this region in the wild-type outer arm. This mutant swam at 119 μm/s at 25°C, i.e., at an intermediate speed between those of wild type (194 μm/s) and of oda-1 (62 μm/s), a mutant missing the entire outer dynein arm. The flagellar beat frequency (∼50 Hz) was also between those of wild type (∼60 Hz) and oda-1 (∼26 Hz). These results indicate that the outer dynein arm of Chlamydomonas can be assembled without the a heavy chain, and that the outer arm missing the α heavy chain retains partial function.