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Selective pressure on the allantoicase gene during vertebrate evolution.
Davide Vigetti1, Giorgio Binelli, Claudio Monetti
1Dipartimento di Biologia Strutturale e Funzionale, Università degli Studi dell'Insubria, Via J.H. Dunant 3, 21100 Varese, Italy.
Journal of Molecular Evolution
|January 28, 2004
Summary
Mammalian genomes retain allantoicase gene sequences, despite lost enzyme activity. Purifying selection suggests this seemingly unnecessary gene is preserved through evolution, with implications for higher vertebrates.
Area of Science:
- Biochemistry
- Evolutionary Biology
- Genomics
Background:
- Vertebrate evolution involves modifications to the uric acid degradation pathway, leading to varied purine catabolism end products.
- Allantoicase, an enzyme in the uricolytic pathway, is active in some fish and amphibians but lost in amniotes.
- Mammalian genomes contain allantoicase mRNA, despite the absence of enzyme activity, prompting investigation into gene preservation.
Purpose of the Study:
- To investigate the reasons behind the continued presence and transcription of allantoicase gene sequences in mammals.
- To analyze the evolutionary conservation of allantoicase sequences across diverse species.
Main Methods:
- Cloning and comparative analysis of allantoicase cDNA sequences from ascidians to mammals.
- Analysis of nonsynonymous-synonymous substitution rates in exons 3-8 of the coding region using maximum likelihood estimation.
Main Results:
- Comparative cDNA analysis revealed conserved allantoicase sequences from ascidians to mammals.
- Purifying selection was detected acting on the allantoicase coding region (exons 3-8), indicating functional constraint.
Conclusions:
- The mammalian genome preserves allantoicase gene sequences and transcription despite the loss of enzyme activity.
- Evidence suggests purifying selection maintains these sequences, implying potential undiscovered functions or regulatory roles in higher vertebrates.