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Abstract: The silkworm Bombyx mori is of great economic value. The B. mori nuclear polyhedrosis virus (BmNPV) is one of the most common and severe pathogens for silkworm. Although certain immune mechanisms exist in silkworms, most silkworms are still susceptible to BmNPV infection. Interestingly, BmNPV infection resistance in some silkworm strains is varied and naturally existing. We have previously established a silkworm strain NB by genetic cross, which is highly resistant to BmNPV invasion. To investigate the molecular mechanism of silkworm resistance to BmNPV infection, we employed proteomic approach and genetic cross to globally identify proteins differentially expressed in parental silkworms NB and 306, a BmNPV-susceptible strain, and their F1 hybrids. In all, 53 different proteins were found in direct cross group (NB♀, 306♂, F1 hybrid) and 21 in reciprocal cross group (306♀, NB♂, F1 hybrid). Gene ontology and KEGG pathway analyses showed that most of these different proteins are located in cytoplasm and are involved in many important metabolisms. Caspase-1 and serine protease expressed only in BmNPV-resistant silkworms, but not in BmNPV-susceptible silkworms, which was further confirmed by Western blot. Taken together, our data suggests that both caspase-1 and serine protease play a critical role in silkworm resistance against BmNPV infection. [Copyright &y& Elsevier]

The application of silkworm hybrids have promoted the innovation and development of agricultural technology, but the mechanism of heterosis in silkworm has not been explained clearly. In this study, the heterosis of silkworm in the aspects of body weight, silk gland and cocoon weight was investigated by means of silkworm hybridization and multi-omics approaches, including transcriptome and proteome. The results showed that heterosis of silkworm body weight, silk gland and cocoon weight was overdominant, but only part of genes and proteins were overdominant, and most of genes and proteins were non-additive. Combined analysis obtained six up-regulated genes and four down-regulated genes that were consistent both in transcriptome and proteome. Gene functional enrichment analysis indicated that most up-regulated genes and proteins were mostly related to metabolism, which led to accelerated metabolism and protein synthesis and contributing to improved heterosis. The up-regulation of 6-phosphate glucose dehydrogenase (G6PDH), phosphatidylethanolamine-binding protein (PEBP) and sHSP20.4, which are involved in metabolism, might be related to silk gland heterosis. A combination of transcriptomic and proteomic analysis was used to understand the molecular mechanism of silkworm heterosis. We found that the phenotypic traits of silkworm are overdominant, while the analysis of transcriptome and proteome showed that only part of genes and proteins were overdominant, and most of genes and proteins were non-additive. Some of the genes had unique expression in F1, which was speculated that genes under heterozygous condition may result in rearrangement and cause metabolic changes in the hybrids. Those both up-regulated in transcriptomic and proteomic analysis were found to be involved in various metabolic processes, so as to accelerate metabolism and protein synthesis, thus exhibiting heterosis. Unlabelled Image • The phenotypic traits of hybrid silkworms showed heterosis. • Most of the genes and proteins in the silk gland of hybrid silkworms were lower than parents. • Accelerated metabolism and protein synthesis in hybrid silkworms contributes to heterosis. • Heterosis may be related to the decreased expression of intracellular transport proteins. [ABSTRACT FROM AUTHOR]

The biological functions of protein glycosylation have been increasingly recognized but not yet been very well understood, especially in lower organisms. Silkworm as a model lepidopteran insect and important economic insect, has been widely studied in life science, however, the current knowledge on the glycosylation status of its proteome is not satisfactory, and little is known about how pathogenic infections could affect the glycosylation status. This study performed large scale glycosite mapping for the silkworm Bombyx mori P50 strain, and quantitatively compared with that infected with the Bombyx mori cytoplasmic polyhedrosis virus (BmCPV). Some 400 glycoproteins were mapped in the silkworm, including N- and O-glycoproteins. Upon virus infection, the glycosylation levels of 41 N-glycopeptides were significantly changed, some of them belonging to transmembrane glycoproteins. The O-glycosylation profiles were also affected. In addition, 4 BmCPV-encoded viral proteins were found to be glycosylated for the first time, including polyhedrin, P101, VP3, and the NS protein. This study drafted a silkworm protein glycosylation map and underlined the potential impact of virus infection on glycosylation. This study reveals the characteristics of the glycoproteome in the silkworm strain P50, and quantitatively compared to that infected by the virus BmCPV, which underlines the impact of virus infection on the alteration of protein glycosylation in invertebrate species. Our findings add to the knowledge of the post translational modifications of this model organism, and also uncovered for the first time the glycosylation status of the viral proteins expressed by BmCPV. Unlabelled Image • Total N- and O-glycoproteins in silkworm strain P50 were revealed. • Alterations in glycosylation profiles were noted after BmCPV virus infection. • The glycosylation status of the BmCPV-encoded proteins was uncovered. [ABSTRACT FROM AUTHOR]