| Budget Amount *help |
¥3,900,000 (Direct Cost: ¥3,600,000、Indirect Cost: ¥300,000)
Fiscal Year 2007: ¥1,300,000 (Direct Cost: ¥1,000,000、Indirect Cost: ¥300,000)
Fiscal Year 2006: ¥2,600,000 (Direct Cost: ¥2,600,000)
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| Research Abstract |
The Chromist hypothesis assumes the host lineages of stramenopiles, cryptomonads, and haptophytes are monophyletic, and a common ancestor of the three "chromist" groups had captured plastids containing chlorophyll a plus c through an endosymbiosis of a red alga. So far, molecular phylogenetic analyses based on nucleus-encoded genes have not recovered the Chromist monophyly as a whole, except a robust sister relationship between cryptomonad and haptophyte host lineages.
A small taxonomic group of heterotrophic unicellular eukaryotes (protists), katablepharids, has been considered as an evolutionary relatives of cryptomonads, whereas the sequence data of this protist lineage has not much accumulated to date. We currently purchased two culture strains of katablepharids, such as Leucocyrptos marina and Katablepharids japonica, and are culturing these cells in our laboratory to determine marker genes for phylogeny from the two katablepharids. In the initial research project, we planned to ma
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ke a cDNA library for these cells, and conduct expressed sequence tags (EST) sequencing on the libraries. Unfortunately, no library is available so far, since it is difficult to eliminate the nucleic acid sample of prey (haptophyte) cells from the cDNA extracted from katablepharids cells. However, we successfully isolated translation elongation factor 2 (EF2) and elongation factor-like genes from L. marina. Interestingly, the robust, clade of haptophytes, cryptomonads, and katablepharids was reconstructed in a preliminary EF2 phylogeny, and this clade further showed affinity to ted algae and green plants. This tree topology obtained from the EF2 analysis suggests that haptophytes, cryptomonads, and katablepharids indeed share a common ancestry to the exclusion of other eukaryotes, and the EF2 gene was laterally transferred from a lineage belong to the Plantae to the ancestral cells of haptophytes, cryptomonads, and katablepharids. On the other hand, phylogenetic of EFL genes reject the monophyly of haptophytes, cryptomonads, and katablepharids, indicating that the three lineages independently acquired EFL genes from three distinctive sources. Less
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