Peptidoglycan Recognition Protein S2 From Silkworm Integument: Characterization, Microbe-Induced Expression, and Involvement in the Immune-Deficiency Pathway

Abstract

Peptidoglycan recognition protein (PGRP) binds specifically to peptidoglycan and plays an important role as a pattern recognition receptor in the innate immunity of insects. The cDNA of a short-type PGRP, an open reading frame of 588 bp encoding a polypeptide of 196 amino acids, was cloned from Bombyx mori. A phylogenetic tree was constructed, and the results showed that BmPGRP-S2 was most similar to Drosophila melanogaster PGRP (DmPGRP-SA). The induced expression profile of BmPGRP-S2 in healthy Escherichia coli- and Bacillus subtilis-challenged B. mori was measured using semiquantitative reverse transcriptase polymerase chain reaction analysis. The expression of BmPGRP-S2 was upregulated at 24 h by E. coli and Ba. subtilis challenge. In addition, in the integument of B. mori, RNAi knockdown of BmPGRP-S2 caused an obvious reduction in the transcription expression of the transcription factor Relish and in antibacterial effector genes Attacin, Gloverin, and Moricin. The results indicated that BmPGRP-S2 participates in the signal transduction pathway of B. mori.

Comparison of gloverin gene expression patterns between domesticated and wild silkworms

“…B. mandarina have been domesticated for at least 5,000 years to increase and improve cocoon yield (Cheng et al, 2015). Recently, genomewide transcriptional analysis of silkworm larvae have found that identified significant upregulation or downregulation of several immune genes (Huang et al, 2009;Yang et al, 2015). This technique has also been used as an efficient method to study adaptation to high-elevation environments or domestication (Cheng et al, 2015).…”

“…This peptide revealed antibacterial activity exclusively against Gram-negative bacteria, showing in many respects activity similar to attacin . In B. mori, four gloverin genes (Bmglv1-4) have been identified (GeneBank accession numbers AB190863, AB190864, Ab190865, and AB190866), and Bmglv2-4 are derived from duplicating Bmglv1 Kawaoka et al, 2008;Mrinal and Nagaraju, 2008;Yang et al, 2015).…”

“…A characteristic of insect immunity is the rapid and transient activation of immune genes to produce effectors in response to microbial infection (Yang et al, 2015). Antimicrobial peptides (AMPs) are an important factor in insect immune response, to combat invading pathogens such as bacteria, fungi, and viruses (Hoffman et al, 1999;Hoffman, 2003;Hultmark, 2003;Kurata et al, 2006;Lemaitre, 2004).…”

“…Hoffman, 2003;Hultmark, 2003;Kurata et al, 2006;Lemaitre, 2004). Insect AMPs are synthesized and regulated by the Toll and immune deficiency (IMD) pathways in the fat body, hemocytes, and other tissues (Bulet et al, 1999;Lemaitre and Hoffmann, 2007;Yang et al, 2015). Several AMPs, cecropin, moricin, attacin and lebocin, which have a broad spectrum of antimicrobial activities, have been identified from the silkworm, B. mori (Hara and Yamakawa, 1995a;Hara and Yamakawa, 1995b;.…”

Molecular cloning and characterization of a short peptidoglycan recognition protein from silkworm Bombyx mori

“…BmPGRP-S1 was the first identified PGRP (Yoshida et al, 1996). BmPGRP-S2 participates in IMD signalling (Yang et al, 2015). BmPGRP-S3 may play an important role in the immune response of the silkworm to B. mori cytoplasmic polyhedrosis virus (BmCPV) infection (Gao et al, 2014).…”