The pathogenicity of different concentrations of Bombyx mori nuclear polyhedrosis virus- Zhenjiang strain (BmNPV ZJ) and Yunnan strain (BmNPV YN) was assessed in Baiyu larvae. The structures of the two viral strains were observed by negative-staining electron microscopy, and their proliferation was examined by quantitative polymerase chain reaction (qPCR). The genomic sequences of these two viruses were obtained to investigate the differences in their pathogenicity. The lethal concentration 50 (LC₅₀) of BmNPV ZJ against Baiyu larvae was higher than that of BmNPV YN, indicating a relatively more robust pathogenicity in BmNPV YN. Electron microscopic images showed that the edges of BmNPV YN were clearer than those of BmNPV ZJ. The qPCR analysis demonstrated significantly higher relative expressions of immediately early 1 gene (ie-1), p143, vp39, and polyhedrin genes (polh) in BmNPV ZJ than in BmNPV YN at 12–96 h. The complete genomes of BmNPV ZJ and BmNPV YN were, respectively, 135,895 bp and 143,180 bp long, with 141 and 145 coding sequences and 40.93% and 39.71% GC content. Considering the BmNPV ZJ genome as a reference, 893 SNP loci and 132 InDel mutations were observed in the BmNPV YN genome, resulting in 106 differential gene sequences. Among these differential genes, 76 (including 22 hub genes and 35 non-hub genes) possessed amino acid mutations. Thirty genes may have been related to viral genome replication and transcription and five genes may have been associated with the viral oral infection. These results can help in understanding the mechanisms of pathogenicity of different strains of BmNPV in silkworms.

Background/Objectives: The body color and patterns of insects play important roles in foraging, evading predators, mating, thermoregulation, and environmental adaptation. During the rearing of the QiufengN silkworm strain, a mutant with black pupal cuticle (QiufengNBP) was discovered. Preliminary map-based cloning and sequence analysis indicated that the ebony gene might significantly influence the formation of the black pupa mutant and the expression of 30K proteins. This study aims to determine the function of the ebony gene and its effect on the expression of the 30K protein during the pupal stage; Methods and Results: We employed CRISPR/Cas9 gene-editing technology to knock out the ebony gene in the Nistari strain, resulting in individuals with black pupae, named Nistari Black Pupa (NisBP). This confirmed that the ebony gene plays a crucial role in black pupa formation. Two-dimensional electrophoresis (2-DE) analysis of the pupal cuticle of NisBP and its wild-type Nistari found that the ebony gene has a significant impact on the expression of 30K proteins, which are vital for embryonic development and serve as key storage proteins; Conclusions: This study is the first to demonstrate that the ebony gene affects the expression of 30K proteins, laying the foundation for further research on their functions and providing insights into the developmental mechanisms of silkworms.

Metabolic syndrome is a global health crisis. However, there are no effective therapeutic strategies for metabolic syndrome. Therefore, this study was conducted to find out a novel silkworm-based metabolic syndrome model that bridges microbial ecology and metabolic dysregulation by integrating hemolymph lipids and midgut microbiota. Our results showed that the levels of HDL-C in the hemolymph of the lean silkworm strain were significantly higher than that in the obese silkworm strain. Furthermore, correlation analysis revealed that Lactococcus and Oceanobacillus were positively related to HDL-C levels, while SM1A02 and Pseudonocardia were negatively associated with HDL-C levels. These relationships between the identified bacteria in the midgut and HDL-C, known as the “good” lipid, in the hemolymph could help guide the development of new treatments for obesity and metabolic problems like high cholesterol in humans. Overall, our results not only established a framework for understanding microbiota-driven lipid dysregulation in silkworms but also offered potential probiotic targets and a bacterial biomarker for obesity and metabolic dysfunction intervention in humans.

Diet plays a critical role in shaping the composition of gut microbiota in insects. Samia ricini, an economically important Lepidoptera insect, is a polyphagous herbivore that offers a useful model for studying dietary effects on the animal gut microbiome. Here, we fed S. ricini larvae with different food plants, Ricinus communis, Ailanthus altissima, and Manihot esculenta leaves to investigate how host plant species influence growth performance, digestive enzyme activities, and the gut microbial community. Our results showed that the Ricinus group exhibited better growth performance. Regarding digestive enzymes, the midgut lipase activity was significantly higher in the Ricinus group than in the Ailanthus group, while no significant differences were observed in α-amylase, cellulase, or trypsin activities among the three groups. Compared to the Manihot group, the Ricinus group showed increased bacterial richness, while the Ailanthus group showed increased bacterial diversity. β-diversity analysis further revealed distinct microbial community structures among all three dietary groups. Specifically, Acinetobacter, Mammaliicoccus, Roseateles, Methylobacterium, Agrobacterium, Faecalibacterium, and Segatella were the dominant bacterial genera. Functional prediction revealed that gut microbes enriched in the Ricinus group were associated with terpenoid/polyketide metabolism, xenobiotics biodegradation, and glycan biosynthesis, whereas those involved in carbohydrate metabolism and biosynthesis of other secondary metabolites were higher in the Manihot group. Spearman correlation analysis indicated that Methylobacterium, Methylorubrum, and Agrobacterium were significantly positively correlated with larval weight, while Staphylococcus and Cyanothece_PCC-7424 exhibited negative correlations. Collectively, these findings suggest a potential association between different plant-derived diets, gut microbiota composition, and host growth performance, highlighting the pivotal role of diet in shaping insect gut microbial communities.

Flavonoids have been implicated in the formation of sex-discriminating fluorescent silkworm cocoons. However, their specific composition in these cocoons remain unexplored. In this study, flavonoid-targeted metabolomics was employed to profile the flavonoid composition of a sex-dependent fluorescent silkworm cocoon strain. Our results revealed comparable total flavonoid content between the violet and yellow fluorescent cocoons, but markedly different flavonoid composition, particularly in a subclass of flavonols. Moreover, four differential flavonoids, baimaside, luteolin-3′,7-di-O-glucoside, quercetin 3,7-diglucoside, and spiraeoside, were identified, among which quercetin 3,7-diglucoside, the most abundant, with levels exceeding the others by an order of magnitude, emerged as the most promising biomarker for the sex-dependent fluorescent phenotypes. These findings pave the way for future investigations into the molecular basis of sex-dependent fluorescent cocoon formation and support the breeding of sex-discriminating fluorescent cocoons for high-quality silk production.