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Molecular evolution of the cecropin multigene family in silkworm Bombyx mori.

ABSTRACT: Cecropins constitute one of the largest and most potent immune protein families found in insect species with diversified numbers and features. In view of the large number of cecropin proteins existing with much sequence variations among them, an overview of the multigene cecropin family in silkworm Bombyx mori was attempted in this study. Cecropin encodes an inducible 64 residue anti-bacterial peptide and was clustered into two groups; first group viz. A and second group including B, D, E and Enbocin. Cecropin A consisted of two sub-groups located on chromosome number 6 of B.mori genome. Cecropin B consisted of six sub-groups, cecropin D and E of one each and Enbocin of two. The second sub-group formed in tandem array of multigene family locus over a length of 78.62 kb on chromosome number 26 in B.mori genome and was organized in positive as well as opposite orientation. The results indicated that cecropin B genes were organized in a close cluster with the intergenic sequence ranging from 1366 bp to 23526 bp. Interestingly a distantly related cecropin E was also located within the cecropin B multigene locus. Similarly distant members like cecropin D and Enbocin were also located in the 3' region of cecropin B locus. The maximum intergenic region of 23526 bp observed between Cecropin D and Enbocin indicates that the two genes were distantly evolved. The phylogenetic analysis clearly indicates a positive correlation between the clusters and physical location on the chromosome, as the length of the intergenic region plays a major role to create newer cecropin families. EST database analysis suggests that most of the cecropin A members were expressed in the microbial fat body while, the cecropin B was equally expressed in fat body and other target tissues. The signal peptides were conserved in all the twelve paralogous gene sequences.

SUBMITTER: Ponnuvel KM

PROVIDER: S-EPMC3040484 | biostudies-literature | 2010 Sep

REPOSITORIES: biostudies-literature

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Molecular evolution of the cecropin multigene family in silkworm Bombyx mori.

Ponnuvel Kangayam M KM Subhasri Natarajan N Sirigineedi Sasibhushan S Murthy Geetha N GN Vijayaprakash Nanjappa B NB

Bioinformation 20100920 3

Cecropins constitute one of the largest and most potent immune protein families found in insect species with diversified numbers and features. In view of the large number of cecropin proteins existing with much sequence variations among them, an overview of the multigene cecropin family in silkworm Bombyx mori was attempted in this study. Cecropin encodes an inducible 64 residue anti-bacterial peptide and was clustered into two groups; first group viz. A and second group including B, D, E and En ...[more]

PMID: 21364788

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Project description:BackgroundNicotinic acetylcholine receptors (nAChRs) mediate fast synaptic cholinergic transmission in the insect central nervous system. The insect nAChR is the molecular target of a class of insecticides, neonicotinoids. Like mammalian nAChRs, insect nAChRs are considered to be made up of five subunits, coded by homologous genes belonging to the same family. The nAChR subunit genes of Drosophila melanogaster, Apis mellifera and Anopheles gambiae have been cloned previously based on their genome sequences. The silkworm Bombyx mori is a model insect of Lepidoptera, among which are many agricultural pests. Identification and characterization of B. mori nAChR genes could provide valuable basic information for this important family of receptor genes and for the study of the molecular mechanisms of neonicotinoid action and resistance.ResultsWe searched the genome sequence database of B. mori with the fruit fly and honeybee nAChRs by tBlastn and cloned all putative silkworm nAChR cDNAs by reverse transcriptase-polymerase chain reaction (RT-PCR) and rapid amplification of cDNA ends (RACE) methods. B. mori appears to have the largest known insect nAChR gene family to date, including nine alpha-type subunits and three beta-type subunits. The silkworm possesses three genes having low identity with others, including one alpha and two beta subunits, alpha 9, beta2 and beta 3. Like the fruit fly and honeybee counterparts, silkworm nAChR gene alpha 6 has RNA-editing sites, and alpha 4, alpha 6 and alpha 8 undergo alternative splicing. In particular, alternative exon 7 of Bm alpha 8 may have arisen from a recent duplication event. Truncated transcripts were found for Bm alpha 4 and Bm alpha 5.ConclusionB. mori possesses a largest known insect nAChR gene family characterized to date, including nine alpha-type subunits and three beta-type subunits. RNA-editing, alternative splicing and truncated transcripts were found in several subunit genes, which might enhance the diversity of the gene family.

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Molecular evolution of the cecropin multigene family in silkworm Bombyx mori.

Publications

Molecular evolution of the cecropin multigene family in silkworm Bombyx mori.

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