SWATH-based quantitative proteomics reveals the mechanism of enhanced Bombyx mori nucleopolyhedrovirus-resistance in silkworm reared on UV-B treated mulberry leaves

Bombyx mori nucleopolyhedrovirus (BmNPV) is one of the most acute infectious diseases in silkworm, which has caused great economic loss in sericulture. Previous study showed that the content of components in mulberry leaves, particularly for moracin N, was increased after UV-B irradiation. In this study, the BmNPV resistance of silkworms reared on UV-B treated and moracin N spreaded mulberry leaves was improved. To uncover the mechanism of enhanced BmNPV resistance, silkworm midguts from UV-B treated mulberry leaves (BUM) and moracin N (BNM) groups were analyzed by SWATH-based proteomic technique. Of note, the abundance of ribosomal proteins in BUM and BNM groups was significantly changed to maintain the synthesis of total protein levels and cell survival. While, cytochrome c oxidase subunit II, calcium ATPase and programmed cell death 4 involved in apoptotic process were up-regulated in BNM group. Expressions of lipase-1, serine protease precursor, Rab1 protein, and histone genes were increased significantly in BNM group. These results suggest that moracin N might be the main active components in UV-B treated mulberry leaves to affect the BmNPV-resistance of silkworm, which could promote apoptotic cell death, enhance the organism immunity, and regulate the intercellular environment of cells in silkworm. It also presents an innovative process to reduce the mortality rate of silkworm infected with BmNPV.

家蚕核型多角体病毒（Bombyx mori nucleopolyhedrovirus, BmNPV）是家蚕最具危害性的急性传染病之一，曾给蚕桑产业造成巨额经济损失。既往研究表明，经紫外-B（UV-B）辐照后的桑叶中多种成分含量显著提升，其中尤以桑辛素N（moracin N）的变化最为突出。本研究针对饲喂经UV-B辐照桑叶及经桑辛素N处理桑叶的家蚕，发现其抗BmNPV能力均得到有效增强。为揭示抗BmNPV能力增强的潜在机制，本研究采用基于SWATH的蛋白质组学技术，对饲喂UV-B辐照桑叶组（BUM组）与饲喂桑辛素N处理桑叶组（BNM组）的家蚕中肠组织开展了蛋白组分析。结果显示，BUM组与BNM组家蚕中肠内的核糖体蛋白丰度均发生显著改变，以维持机体总蛋白质合成水平与细胞存活稳态。在BNM组中，参与细胞凋亡过程的细胞色素c氧化酶亚基II、钙ATP酶及程序性细胞死亡蛋白4的表达量均显著上调；同时，脂肪酶-1、丝氨酸蛋白酶前体、Rab1蛋白及组蛋白基因的表达水平亦明显升高。上述研究结果提示，桑辛素N或是UV-B辐照桑叶中赋予家蚕抗BmNPV能力的核心活性成分，其可通过促进细胞凋亡、增强机体免疫及调控家蚕细胞间微环境来发挥抗病原作用。本研究同时为降低BmNPV感染家蚕的死亡率提供了一种创新性的技术方案。