Identification of Peritrophins and Antiviral Effect of Bm01504 against BmNPV in the Silkworm, Bombyx mori.

Xu-Le Zha,Yi-Hong Shen,Xin-Bo Yu,Xian-Zhi Huang,Hong-Yan Zhang,Cheng Lu,Han Wang

doi:10.3390/ijms21217973

Xu-Le Zha, Yi-Hong Shen + Show 5 more

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https://doi.org/10.3390/ijms21217973

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Abstract

The insect midgut secretes a semi-permeable, acellular peritrophic membrane (PM) that maintains intestinal structure, promotes digestion, and protects the midgut from food particles and pathogenic microorganisms. Peritrophin is an important PM protein (PMP) in the PM. Here, we identified 11 peritrophins with 1–16 chitin binding domains (CBDs) comprising 50–56 amino acid residues. Multiple CBDs in the same peritrophin clustered together, rather than by species. The CBD contained six highly conserved cysteine residues, with the key feature of amino acids between them being CX11-15CX5CX9-14CX11-12CX6-7C. Peritrophins with 2 and 4 CBDs (Bm09641 and Bm01504, respectively), and with 1, 8, and 16 CBDs (Bm11851, Bm00185, and Bm01491, respectively) were mainly expressed in the anterior midgut, and throughout the midgut, respectively. Survival rates of transgenic silkworms with Bm01504 overexpression (Bm01504-OE) and knockout (Bm01504-KO) infected with B. mori nucleopolyhedrovirus (BmNPV) were significantly higher and lower, whereas expression of the key viral gene, p10, were lower and higher, respectively, compared with wild type (WT). Therefore, Bm01504-OE and Bm01504-KO transgenic silkworms were more and less resistant, respectively, to BmNPV. Bm01504 plays important roles in resisting BmNPV invasion. We provide a new perspective for studying PM function, and reveal how the silkworm midgut resists invasive exogenous pathogenic microorganisms.

Highlights

Insect midgut secretes a semi-permeable peritrophic membrane (PM) that protects midgut epithelial cells from damage by food particles, toxic compounds and invasive pathogenic microorganisms [1,2,3,4,5,6]
A total of 40 proteins containing the peritrophin-A domain were identified in the silkworm genome database based on the Hidden Markov Model (HMM) of the CBM_14 family (Table S1)
According to the type of conserved domain and evolutionary characteristics of the chitin binding domains (CBDs), these genes were divided into CHTs (n = 3), mucins (MUC; n = 4), chitin deacetylases (CDAs) (n = 3), CPAP1 (n = 13), CPAP3 (n = 6), and peritrophins (n = 11) (Table 1)

Summary

Introduction

Insect midgut secretes a semi-permeable peritrophic membrane (PM) that protects midgut epithelial cells from damage by food particles, toxic compounds and invasive pathogenic microorganisms [1,2,3,4,5,6]. Biological or chemical methods have been successfully used to destroy the PM structure as a means of pest control [7,8,9,10,11,12]. Shi et al (2004) proposed a structural model of PM, in which chitin microfibrils consisting of 20–400 chitin chains assemble into chitin bundles to form the backbone of the PM network, and PM protein (PMP) adheres to chitin via non-covalent bonding or chitin binding domains (CBD) [15]. According to the degree of binding with PM, PMPs can be categorized into four classes. PMPs of class I–III can be removed from the PM by physiological buffers, mild detergents, such as Triton X-100, and strong detergents, such as urea, respectively; class IV proteins cannot be removed by these three methods. Class III is named peritrophins that contains at least one CBD [16]

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