THE CHLAMYDOMONAS-REINHARDTII ODA3 GENE ENCODES A PROTEIN OF THE OUTER DYNEIN ARM DOCKING COMPLEX

We have used an insertional mutagenesis/gene tagging technique to gene rate new Chlamydomonas reinhardtii mutants that are defective in assem bly of the outer dynein arm. Among 39 insertional oda mutants characte rized, two are alleles of the previously uncloned ODA3 gene, one is an allele of the uncloned ODA10 gene, and one represents a novel ODA gen e (termed ODA12). ODA3 is of particular interest because it is essenti al for assembly of both the outer dynein arm and the outer dynein arm docking complex (ODA-DC) onto flagellar doublet microtubules (Takada, S., and R. Kamiya. 1994. J. Cell Biol. 126:737-745). Beginning with th e inserted DNA as a tag, the ODA3 gene and a full-length cDNA were clo ned. The cloned gene rescues the phenotype of oda3 mutants. The cDNA s equence predicts a novel 83.4-kD protein with extensive coiled-coil do mains. The ODA-DC contains three polypeptides; direct amino acid seque ncing indicates that the largest of these polypeptides corresponds to ODA3. This protein is likely to have an important role in the precise positioning of the outer dynein arms on the flagellar axoneme.