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Sequence analysis and evolutionary aspects of piscine alpha-1-microglobulin/bikunin mRNA transcripts
S Hanley1, J O McInerney, R Powell
1Department of Microbiology, University College Galway, Ireland.
Abstract:
Studies on mammalian alpha-1-microglobulin/bikunin (AMBP) protein sequences suggest the ancestral AMBP gene arose between 270 and 80 million years ago. Here we report a similar study including recently reported piscine AMBP messenger RNA sequences. The analysis implies a far earlier data for the assembly of the ancestral AMBP gene, more than 450 million years ago. Similarly, a revised date for the origin of the ancestral Kunitz-type protein is estimated at approximately 875 million years ago. Evolutionary conservation is apparent among all the AMBP amino acid sequences. This implies a common functional significance in both teleosts and mammals. However, an unusually rapid rate of evolution is observed for domain II of the piscine bikunin sequences, suggesting that this domain is no longer truly orthologous in fish.
Insights
The ancestral alpha-1-microglobulin/bikunin (AMBP) gene is now estimated to be over 450 million years old, originating much earlier than previously thought. This suggests a conserved function across mammals and fish, though some fish protein domains show rapid evolution.
Area of Science:
- Evolutionary biology
- Genomics
- Biochemistry
Background:
- The alpha-1-microglobulin/bikunin (AMBP) protein is found in mammals and plays various roles.
- Previous studies estimated the origin of the ancestral AMBP gene to be between 270 and 80 million years ago.
Purpose of the Study:
- To investigate the evolutionary history of the AMBP gene by including piscine (fish) sequences.
- To refine the estimated origin date of the ancestral AMBP gene and related protein domains.
Main Methods:
- Comparative sequence analysis of mammalian and piscine AMBP messenger RNA (mRNA) and protein sequences.
- Phylogenetic analysis to estimate divergence times.
Main Results:
- The analysis of piscine AMBP mRNA sequences suggests the ancestral AMBP gene originated over 450 million years ago, significantly earlier than prior estimates.
- The origin of the ancestral Kunitz-type protein domain was revised to approximately 875 million years ago.
- Evolutionary conservation of AMBP sequences indicates a common functional significance in teleosts (fish) and mammals.
- Domain II of piscine bikunin sequences exhibits an unusually rapid rate of evolution, suggesting a loss of strict orthology in fish.
Conclusions:
- The ancestral AMBP gene is considerably older than previously determined, with origins predating the diversification of many vertebrate groups.
- While core AMBP functions appear conserved, rapid evolution in specific domains like piscine bikunin domain II highlights adaptive changes and potential functional divergence in fish.
- This study provides new insights into the deep evolutionary history and functional diversification of the AMBP gene family across vertebrates.