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Two separate genes encode the catalytic 70 kDa V-ATPase subunit in Psilotum and Equisetum
T Starke1, T P Linkkila, J P Gogarten
1Department of Molecular and Cell Biology, University of Connecticut, Storrs 06269.
Summary
Two genes for the vacuolar-type proton ATPase (V-ATPase) catalytic subunit were discovered in two plant species. This finding suggests gene duplication and subsequent evolutionary pressures on V-ATPase genes in plants.
Area of Science:
- Plant molecular biology
- Cellular and subcellular biology
- Evolutionary genetics
Background:
- Vacuolar-type proton ATPases (V-ATPases) are essential proton pumps found on various endomembranes in eukaryotic cells.
- Despite their crucial roles in diverse cellular compartments, typically only one gene per V-ATPase subunit is found per genome.
- The evolutionary history and gene duplication events of V-ATPase subunits in plants remain largely unexplored.
Purpose of the Study:
- To investigate the presence and evolutionary dynamics of genes encoding the catalytic subunit of V-ATPase in primitive plant species.
- To determine if gene duplication events have occurred for the V-ATPase catalytic subunit in selected plant lineages.
- To analyze the selective pressures and evolutionary mechanisms acting on duplicated V-ATPase genes.
Main Methods:
- Polymerase Chain Reaction (PCR) across intron-exon boundaries was employed to identify V-ATPase genes.
- Sequence analysis was performed to compare gene similarities within and between species.
- Substitution rates at codon positions and analysis of intervening sequences were used to infer evolutionary pressures and mechanisms.
Main Results:
- Two distinct genes encoding the V-ATPase catalytic subunit were identified in *Psilotum nudum* and *Equisetum arvense*.
- In *Psilotum nudum*, both genes are transcribed and under selection pressure, indicating functional relevance.
- Evidence suggests gene conversion mechanisms played a role in maintaining similarity between duplicated genes, with notable conservation in intervening sequences.
Conclusions:
- Gene duplication of the V-ATPase catalytic subunit has occurred in *Psilotum* and *Equisetum*.
- The duplicated genes in *Psilotum* are under evolutionary selection, suggesting functional divergence or specialization.
- Unexpected conservation of intervening sequences warrants further investigation into potential regulatory roles or structural constraints.