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.

The transcriptome of Spodoptera exigua larvae exposed to different types of microbes

“…Cecropins from B. mori have been characterized and 12 paralogous genes have been identified in its genome (Fig. 5A) (Ponnuvel et al, 2010). In order to estimate the minimum number of cecropins in S. exigua and to determine their evolutionary origin, a phylogenetic tree was reconstructed with B. mori and S. exigua cecropins (Fig.…”

Sequence diversity and evolution of antimicrobial peptides in invertebrates

“…The cecropin family is classified into five 391 sub-types (cecropin A-E) and the members of the cecropin multi-392 gene family varied among the species. Cecropin from B. mori was 393 comprised of 13 genes divided into members of four cecropin 394 sub-types (A, B, D and E but not C)(Ponnuvel et al, 2010). Recently, 395 transcriptomic analysis of pathogen-related genes in S. exigua iden-396 tified 10 different genes coding for cecropin that can be divided 397 into six subfamilies (A-F)(Pascual et al, 2012).…”

Cecropins from Plutella xylostella and Their Interaction with Metarhizium anisopliae

“…On the other hand, all functional genes were expressed, mainly in fat bodies after bacterial infection, although at different stages of development in D . melanogaster [ 23 ], but the expression of cecropins after fungal induction has not been reported in P . xylostella .…”

“…In Drosophila melanogaster , the cecropin multigenes family consists of both four functional genes (Cecropin A1, A2, B and C), two pseudo-genes (Cecropin 1 and 2) and the functional genes coding for cecropins [ 21 , 22 ]. On bacterial infection, all functional genes are expressed mainly in the fat bodies at different developmental stages [ 23 ]. Cecropin A1 and A2 are mainly expressed in larvae and adults, while, B and C are mostly expressed during the pupal stage [ 22 ].…”