Open Access Research article

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

Ping Zhao1, Gen-Hong Wang12, Zhao-Ming Dong1, Jun Duan12, Ping-Zhen Xu1, Ting-Cai Cheng12, Zhong-Huai Xiang1 and Qing-You Xia12*

Author Affiliations

1 The Key Sericultural Laboratory of Agricultural Ministry, Southwest University, Chongqing 400715, PR China

2 The Institute of Agricultural and Life Sciences, Chongqing University, Chongqing 400044, PR China

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BMC Genomics 2010, 11:405  doi:10.1186/1471-2164-11-405

Published: 24 June 2010



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. Genome-wide identification and expression analysis of serine proteases and their homologs in the silkworm might provide valuable information about their biological functions.


In 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.


Silkworm 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.