The peculiar distribution of class I and class II aldolases in diatoms and in red algae |
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Authors: | Peter G Kroth Yvonne Schroers Oliver Kilian |
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Institution: | 1. Fachbereich Biologie, Universit?t Konstanz, Postfach M611, Konstanz, Germany 2. Lorettostr. 33, 40219, Düsseldorf, Germany 3. Department of Plant Biology, Carnegie Institution of Washington, 260 Panama Street, Stanford, CA, 94305, USA
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Abstract: | Diatom plastids probably evolved by secondary endocytobiosis from a red alga that was up by a eukaryotic host cell. Apparently,
this process increased the complexity of the intracellular distribution of metabolic enzymes. We identified genes encoding
fructose-bisphosphate aldolases (FBA) in two centric (Odontella sinensis, Thalassiosira pseudonana) and one pennate (Phaeodactylum tricornutum) diatoms and found that four different aldolases are present in both groups: two plastid targeted class II enzymes (FBAC1
and FBAC2), one cytosolic class II (FBA3) and one cytosolic class I (FBA4) enzyme. The pennate Phaeodactylum possesses an additional plastidic class I enzyme (FBAC5). We verified the classification of the different aldolases in the
diatoms by enzymatic characterization of isolated plastids and whole cell extracts. Interestingly, our results imply that
in plastids of centric and pennate diatoms mainly either class I or class II aldolases are active. We also identified genes
for both class I and class II aldolases in red algal EST databases, thus presenting a fascinating example of the reutilization
and recompartmentalization of different aldolase isoenzymes during secondary endocytobiosis but as well demonstrating the
limited use of metabolic enzymes as markers for the interpretation of phylogenetic histories in algae.
The nucleotide sequences have been deposited at Genbank under the accession numbers AY116588, AY191866 and AY212505 |
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Keywords: | Aldolase Diatom Intron Plastid Targeting |
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