Phylogenetic analysis of chromophyte-related colorless flagellates

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The chromophytes or hetrokoint algae is a huge assemblage of autotrophic eukaryotes and as big as the green plants. It comprises various classes of chlorophyll c containing algae such as the Chrysophyceae, Bacillariophyceae, Xanthophyceae, Raphidophyceae and Phaeophyceae. In the lineage of the chromophytes, heterotrophic taxa are also included. These are oomycete fungi (pseudofungi), hyphochytrids, labyrhintulids (net slime molds), which were traditionally classified as fungi, and protozoan flagellates bisocoecids. The taxon including both autotrophic chromophytes and heterotrophic fungi and flagellates is called the stramenopiles, and the chromophytes is believed to have arisen from heterotrophic members through acquisition of the chloroplast by secondary endosymbiosis of red-algae related eukaryote.General ultrastructure and the flagellar apparatus of Cafeteria, a member of the bicosoecids, was examined and compared with chromophyte algae. It was revealed that Cafeteria had homologou … More s flagella/basal bodies and flagellar rootlets. The R3 was especially important, because it was responsible for feeding food particles and food uptake took place in the area between two split bundles of microtubules of the R3 just as in Ochromonas and allied genera (Ochromonadales) in the Chrysophyceae. This result suggested that the phagocytotic ability known in the Chrysophyceae was a symplesiomorphy which appeared in early evolution of the stramenopiles.Developayella sp. nov. (taxon incertae sedis) was also examined. It also had the R3 similar to Cafeteria and food uptake took place at the same portion of the cell, suggesting the R3-mediated feeding is widely distributed in heterotrophic flagellates of the stramenopiles. In Developayella double helix, a structure similar to that of the oomycete fungi, is present. Phylogenetic analysis suggested that Developayella was a close relative of the oomycete fungi. Based on ultrastructural comparison and 18SrDNA analyses, early evolution of the stramenopiles was discussed. Less