ABSTRACT
Analyses of Chlamydomonas dynein-deficient mutants and in vitro motility assays on isolated dyneins indicate striking functional diversity among various axonemal dyneins. Studies with Chlamydomonas mutants suggest that outer-arm dynein is important for flagellar beating at high frequency, while inner-arm dyneins are important for beating with a proper waveform. The variety of dynein species and their functions have been most extensively studied using Chlamydomonas, the model organism for cilia/flagella research. Assignment of isolated dynein subunits with particular dynein arms was first made possible by the isolation of Chlamydomonas mutants lacking either of the arms. The variety and subunit composition of inner-arm dyneins have been extensively analyzed only in Chlamydomonas. Phylogenetic analyses of heavy chains in various organisms indicated that the axonemal dynein sequences can be classified into seven or eight types: two or three for outer-arm dynein, two for two-headed inner-arm dynein, and three for one-headed dynein.
