Contrasting evolutionary histories of chloroplast thioredoxins f and m |
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Authors: | Hartman H; Syvanen M; Buchanan BB |
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Institution: | Department of Plant Biology, University of California, Berkeley 94708. |
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Abstract: | Fourteen thioredoxin sequences were used to construct a minimal
phylogenetic tree by using parsimony. The bacterial thioredoxins clustered
into three groups: one containing the photosynthetic purple bacteria,
Escherichia and Corynebacterium; a second containing the photosynthetic
green bacterium, Chlorobium; and a third containing cyanobacteria. These
groupings are similar to those generated from earlier 16s RNA analyses.
Animal thioredoxins formed a fourth group. The two thioredoxins of
chloroplasts (f and m) showed contrasting phylogenetic patterns. As
predicted from prior studies, spinach chloroplast thioredoxin m grouped
with its counterparts from cyanobacteria and eukaryotic algae, but,
unexpectedly, thioredoxin f grouped with the animal thioredoxins. The
results indicate that, during evolution, thioredoxin m of contemporary
photosynthetic eukaryotic cells was derived from a prokaryotic symbiont,
whereas thioredoxin f descended from an ancestral eukaryote common to
plants and animals. The findings illustrate the potential of thioredoxin as
a phylogenetic marker and suggest a relationship between the animal and
f-type thioredoxins.
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Keywords: | |
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