A Novel Digestive Proteinase Lipase Member H-A in Bombyx mori Contributes to Digestive Juice Antiviral Activity Against B. mori Nucleopolyhedrovirus.

Shang-Zhi Zhang,Lin-Bao Zhu,Xue Kong,Ling-Ling You,Jie Wang,Yu-Ling Wang,Shahzad Toufeeq,Ying-Xue Liu,Hui-Hua Cao,Jia-Ping Xu

doi:10.3390/insects11030154

Abstract

Previous studies have revealed that some proteins in Bombyx mori larvae digestive juice show antiviral activity. Here, based on the label-free proteomics data, BmLipase member H-A (BmLHA) was identified as being involved in the response to BmNPV infection in B. mori larvae digestive juice. In the present study, a gene encoding the BmLHA protein in B. mori was characterized. The protein has an open reading fragment of 999 bp, encoding a predicted 332 amino acid residue-protein with a molecular weight of approximately 35.9 kDa. The phylogenetic analysis revealed that BmLHA shares a close genetic distance with Papilio xuthus Lipase member H-A. BmLHA was highly expressed in the middle part of the B. mori gut, and the expression level increased with instar rising in larvae. There was higher expression of BmLHA in A35 than in P50 strains, and it was upregulated in both A35 and P50 strains, following BmNPV infection. The expression level of VP39 decreased significantly in appropriate recombinant-BmLHA-treated groups compared with the PBS-treated group in B. mori larvae and BmN cells. Meanwhile, overexpression of BmLHA significantly reduced the infectivity of BmNPV in BmN cells. These results indicated that BmLHA did not have digestive function but had anti-BmNPV activity. Taken together, our work provides valuable data for the clarification of the molecular characterization BmLHA and supplements research on proteins of anti-BmNPV activity in B. mori.

Highlights

The silkworm Bombyx mori L. (Lepidoptera: Bombycidae) has been domesticated for more than 5000 years and still plays an important role in many developing countries
In our previous study, based on the label-free proteomics data of B. mori larvae digestive juice, we found that the Lipase member H-A(BmLHA) showed upregulation in midgut digestive juice of the resistant strain (A35) compared to the susceptible strain (P50) [32]
The results showed that BmLipase member H-A (BmLHA) and its homologs from seven other insects were clustered into the Lepidoptera group (Figure 2C), and it shares a close genetic distance with Papilio xuthus

Summary

Introduction

The silkworm Bombyx mori L. (Lepidoptera: Bombycidae) has been domesticated for more than 5000 years and still plays an important role in many developing countries. (Lepidoptera: Bombycidae) has been domesticated for more than 5000 years and still plays an important role in many developing countries. B. mori is a good model organism for the study of insect genetics and immunology [1,2]. B. mori nucleopolyhedrovirus (BmNPV), is a major cause of silkworm death and leads to the largest sericulture industry losses annually. BmNPV is a major viral pathogen and still remains a significant challenge to the sericulture industry due to a lack of effective prevention methods. BmNPV belongs to the Baculoviridae family and is characterized by a rod-shaped, enveloped virion containing a closed, circular, double-stranded DNA genome of ~130 kilobase-pairs (kb) in length [3,4].

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