Molecular evolution of the Cecropin multigene family in Drosophila: functional genes vs. pseudogenes

• Published in: Genetics (Austin) Vol. 150; no. 1; pp. 157 - 171
• Main Authors: Ramos-Onsins, S. (Universitat de Barcelona, Spain.), Aguade, M
• Format: Journal Article
• Language: English
• Published: United States Genetics Soc America 01.09.1998; Genetics Society of America
• Subjects: Amino Acid Sequence; AMINO ACID SEQUENCES; Animals; ANTIBACTERIAL PEPTIDES; Base Sequence; CHEMICAL COMPOSITION; DELETIONS; DNA; DROSOPHILA; Drosophila - genetics; DROSOPHILA MAURITIANA; DROSOPHILA MELANOGASTER; DROSOPHILA SECHELLIA; DROSOPHILA SIMULANS; Evolution; Evolution, Molecular; GENBANK/Y16852; GENBANK/Y16853; GENBANK/Y16854; GENBANK/Y16855; GENBANK/Y16856; GENBANK/Y16857; GENBANK/Y16858; GENBANK/Y16859; GENBANK/Y16860; GENBANK/Y16861; GENBANK/Y16862; GENBANK/Y16863; GENE EXPRESSION; GENES; GENETIC POLYMORPHISM; Genetics; Insect Proteins - genetics; Insects; MOLECULAR SEQUENCE DATA; MULTIGENE FAMILIES; Multigene Family; NUCLEOTIDE SEQUENCE; PEPTIDES; Polymorphism, Genetic; PROMOTERS; PSEUDOGENES; Sequence Homology, Amino Acid; Sequence Homology, Nucleic Acid; Species Specificity; STRUCTURAL GENES; TRANSCRIPTION
• ISSN: 0016-6731; 1943-2631; 1943-2631
• DOI: 10.1093/genetics/150.1.157

Approximately 4 kb of the Cecropin cluster region have been sequenced in nine lines of Drosophila melanogaster and one line of the sibling species D. simulans, D. mauritiana, and D. sechellia. This region includes three functional genes (CecA1, CecA2, and CecB), which are involved in the insect immune response, and two pseudogenes (CecPsi1 and CecPsi2). The level of silent polymorphism in the three Cec genes is rather high (0.028), and there is no excess of nonsynonymous polymorphism. There is no evidence of gene conversion in the history of these genes. The interspecific comparison has revealed that in the three species of the simulans cluster the CecA2 gene is partially deleted and has therefore lost its function and become a pseudogene; in each of the species, subsequent deletions have accumulated. Divergence estimates indicate that the CecPsi1 and CecPsi2 pseudogenes are highly diverged, both between themselves and relative to the other three Cec genes. However, both CecPsi1 and CecPsi2 have conserved transcriptional signals and splice sites, and they present an open reading frame; also, correctly spliced transcripts have been detected for both CecPsi1 and CecPsi2. The data support that these genes are either active genes with some null alleles or young pseudogenes.