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Structural similarities between psbA genes from red and brown algae
T Winhauer1, S Jäger, K Valentin
1Justus Liebig Universität, Institut für Pflanzenphysiologie, Giessen, Federal Republic of Germany.
Current Genetics
|July 1, 1991
Summary
The psbA genes of red and brown algae share a unique 21 bp insertion, suggesting a close evolutionary relationship between their plastids. This finding supports the polyphyletic origin of plastids, with implications for algal evolution.
Area of Science:
- * Molecular biology
- * Phycology
- * Evolutionary biology
Background:
- * The evolutionary origins of plastids, the sites of photosynthesis in eukaryotic algae and plants, remain a subject of intense research.
- * Previous studies suggest a polyphyletic origin, with different algal lineages acquiring plastids through independent endosymbiotic events.
- * The psbA gene, encoding a key protein in photosystem II, is a useful marker for studying plastid evolution.
Purpose of the Study:
- * To investigate the evolutionary relationship between red and brown algae by analyzing their psbA genes.
- * To compare the psbA gene sequences of Antithamnion spec. (red alga) and Ectocarpus siliculosus (brown alga) with those of other photosynthetic organisms.
- * To assess the implications of these findings for the hypothesis of a polyphyletic origin of plastids.
Main Methods:
- * Cloning and sequencing of single-copy psbA genes from Antithamnion spec. and Ectocarpus siliculosus.
- * Detection of monocistronic transcripts for the psbA genes.
- * Comparative sequence analysis of psbA genes, including identification of insertions and deletions.
Main Results:
- * The psbA genes from both Antithamnion spec. and Ectocarpus siliculosus were successfully cloned and sequenced.
- * A conserved 21 bp insertion was identified at the 3' end of both algal psbA genes, a feature also present in cyanobacteria.
- * This insertion was absent in the chloroplast psbA genes of Prochlorothrix hollandica, a chlorophyll b-containing organism.
Conclusions:
- * The presence of the 21 bp insertion in the psbA genes of red and brown algae suggests a close evolutionary relationship between their plastids.
- * These findings provide molecular evidence supporting the hypothesis that plastids originated from multiple endosymbiotic events (polyphyletic origin).
- * The data indicate that the plastids of red and brown algae are more closely related to each other than to those of other algal groups examined.