Proteins related to green algal striated fiber assemblin are present in stramenopiles and alveolates

In green algae, striated fiber assemblin (SFA) is the major protein of the striated microtubule-associated fibers that are structural elements in the flagellar basal apparatus. Using Basic Local Alignment Search Tool (BLAST) searches of recently established databases, SFA-like sequences were detected in the genomes not only of green algal species but also of a range of other protists. These included species in two alveolate subgroups, the ciliates (Tetrahymena thermophila, Paramecium tetraurelia) and the dinoflagellates (Perkinsus marinus), and two stramenopile subgroups, the oomycetes (Phytophthora sojae, Phytophthora ramorum, Phytophthora infestans) and the diatoms (Thalassiosira pseudonana, Phaeodactylum tricornutum). Together with earlier identification of SFA-like sequences in the apicomplexans, these results indicate that homologs of SFA are present across the alveolates and stramenopiles. Antibodies raised against SFA from the green alga, Spermatozopsis similis, react in immunofluorescence assays with the two basal bodies and an anteriorly directed striated fiber in the flagellar apparatus of biflagellate Phytophthora zoospores.