Characterization and genomic organization of esterase gene in silkworm, Bombyx mori L.

Abstract

N-terminal amino acid sequence of esterase gene was blast searched with Bombyx mori EST (expressed sequence tag) database. EST clone fbpv0006 showed 95% homology with N-terminal sequence of esterase protein. Further, the genomic organization of exons and introns were identified using the EST clone sequence. The results on genomic organization of esterase gene indicated that the blood esterase gene possesses two exons with varying length of 192 and 524 bp, and a long intron of 2124 bp length present between these two exons. The primers were designed to the intron and exon regions and the fragments were PCR amplified using genomic DNA from silk moth as template. The amplicon showed a mol wt 799 bp in the intron region and 547 bp covering the exon regions. When the esterase genes from two multivoltine (Pure Mysore & PMX) and bivoltine (NB4D2 & CSR-19) races, possessing contrasting characters to thermal tolerance, were PCR amplified and products were sequenced. The two sequences showed 97% homology with 3% mismatch through pair blast analysis. Furthermore, per cent identity per exon, number of gaps per exon, overall per cent identity, per cent coverage of the mRNA, number of splice donor sites, presence or absence of splice donor and acceptor sites for each exon were inferred through spidey programme. Also, the phylogenetic relationship of B. mori esterase gene sequence was compared with other organisms through Clustal W analysis and a dendogram was projected. The projection showed that majority of insect esterases formed a major separate cluster, while B. mori esterase clustered with aphid insect esterases.