Genome-wide identification and expression analysis of serine proteases and homologs in the silkworm Bombyx mori

Ping Zhao,Gen-Hong Wang,Ting-Cai Cheng,Ping-Zhen Xu,Zhong-Huai Xiang,Zhao-Ming Dong,Jun Duan,Qing-You Xia

doi:10.1186/1471-2164-11-405

Ping Zhao, Gen-Hong Wang + Show 6 more

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https://doi.org/10.1186/1471-2164-11-405

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Abstract

BackgroundSerine proteases (SPs) and serine proteases homologs (SPHs) are a large group of proteolytic enzymes, with important roles in a variety of physiological processes, such as cell signalling, defense and development. Genome-wide identification and expression analysis of serine proteases and their homologs in the silkworm might provide valuable information about their biological functions.ResultsIn this study, 51 SP genes and 92 SPH genes were systematically identified in the genome of the silkworm Bombyx mori. Phylogenetic analysis indicated that six gene families have been amplified species-specifically in the silkworm, and the members of them showed chromosomal distribution of tandem repeats. Microarray analysis suggests that many silkworm-specific genes, such as members of SP_fam12, 13, 14 and 15, show expression patterns that are specific to tissues or developmental stages. The roles of SPs and SPHs in resisting pathogens were investigated in silkworms when they were infected by Escherichia coli, Bacillus bombysepticus, Batrytis bassiana and B. mori nucleopolyhedrovirus, respectively. Microarray experiment and real-time quantitative RT-PCR showed that 18 SP or SPH genes were significantly up-regulated after pathogen induction, suggesting that SP and SPH genes might participate in pathogenic microorganism resistance in B. mori.ConclusionSilkworm SP and SPH genes were identified. Comparative genomics showed that SP and SPH genes belong to a large family, whose members are generated mainly by tandem repeat evolution. We found that silkworm has species-specific SP and SPH genes. Phylogenetic and microarray analyses provide an overview of the silkworm SP and SPHs, and facilitate future functional studies on these enzymes.

Highlights

Serine proteases (SPs) and serine proteases homologs (SPHs) are a large group of proteolytic enzymes, with important roles in a variety of physiological processes, such as cell signalling, defense and development
The genes were named BmSP(H)1-BmSP(H)143 (Additional file 1), 20 of which had previously been submitted to GenBank, including ovarian serine protease (GenBank Accession No AAL62027), cocoonase (GenBank Accession No ABR14241), vitellin-degrading protease precursor (GenBank Accession No BAA03758), and alkaliphilic serine protease P-Iic (GenBank Accession No AAB26023) (Additional file 3), which function in digestion, ovary and embryo development, and formation of fibroin
When we compared the magnitude in induction of gene expression between antibacterial proteins BmcecropinB and silkworm SP or SPH genes, we found that BmcecropinB was remarkably upregulated on infection by these four pathogens at all time points except for B. mori nucleopolyhedrovirus (BmNPV) infection at 24 h (Figure 6)

Summary

Introduction

Serine proteases (SPs) and serine proteases homologs (SPHs) are a large group of proteolytic enzymes, with important roles in a variety of physiological processes, such as cell signalling, defense and development. Genomewide identification and expression analysis of serine proteases and their homologs in the silkworm might provide valuable information about their biological functions. Serine proteases (SPs) in the S1 family are involved in physiological processes including digestion, development and defense [1,2,3]. X-ray crystallography studies show that the active center of bovine chymotrypsin is Ser195, His, and Asp102 [4,5]. SPs are divided into several types, including the trypsin, chymotrypsin and elastase, based on the target scissile bond. SP zymogens are sequentially activated in a cascade pathway, with a classic example

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