| Budget Amount *help |
¥3,600,000 (Direct Cost: ¥3,600,000)
Fiscal Year 2003: ¥1,700,000 (Direct Cost: ¥1,700,000)
Fiscal Year 2002: ¥1,900,000 (Direct Cost: ¥1,900,000)
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| Research Abstract |
One of the most important problem remaining in the phylogeny of green plants is which is the earliest land plant. We have determined the complete structure of the chloroplast genome from hornwort which had been expected as the earliest land plant. ML tree, based on 10,854 amino acid sites from 51 protein genes which are commonly found in the known chloroplast genomes, revealed that bryophytes are monophyletic with high statistical confidence and form the earliest branch, which diverged from all the other main lineages of land plants. The tree shows that the hornwort is basal in bryophytes.
Another important problem, which is the direct ancestor of land plants, is in progress by analyzing the complete chloroplast structure from a charales which is expected as the direct ancestor of land plants.
Much more RNA editing sites have been found in the hornwort chloroplast than those in the other chloroplasts. They contained 436 sites of U to C conversion which is not observed any seed plants. These editing converts more than half the genes functional, and creates the anticodon of a tRNA and the sequence required for splicing. Almost all the RNA editing complementing the mutation in the genes would be required in early land plants, because RNA editing is not seen in the algae but seen in almost all land plants.
The sequence, named distant cis-recognition element (DGRE), complementary to the edited sequence has been observed within the same RNA. The premature transcript could form double stranded structure where there is a mismatch in base pairing. The mismatch could be recognized, and corrected by editing enzyme. This hypothetical mechanism for RNA editing will be proven in vitro.
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