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Fluoride tolerance is an economically important trait of silkworm. Near-isogenic lines (NILs) of the dominant endurance to fluoride ( Def ) gene in Bombyx mori has been constructed before. Here, we analyzed the gene expression profiles of midgut of fluoride-sensitive and fluoride-endurable individuals of Def NILs by using high-throughput Illumina sequencing technology and bioinformatics tools, and identified differentially expressed genes between these individuals. A total of 3,612,399 and 3,567,631 clean tags for the libraries of fluoride-endurable and fluoride-sensitive individuals were obtained, which corresponded to 32,933 and 43,976 distinct clean tags, respectively. Analysis of differentially expressed genes indicates that 241 genes are differentially expressed between the two libraries. Among the 241 genes, 30 are up-regulated and 211 are down-regulated in fluoride-endurable individuals. Pathway enrichment analysis demonstrates that genes related to ribosomes, pancreatic secretion, steroid biosynthesis, glutathione metabolism, steroid biosynthesis, and glycerolipid metabolism are down-regulated in fluoride-endurable individuals. qRT-PCR was conducted to confirm the results of the DGE. The present study analyzed differential expression of related genes and tried to find out whether the crucial genes were related to fluoride detoxification which might elucidate fluoride effect and provide a new way in the fluorosis research. [ABSTRACT FROM AUTHOR]

Abstract: A novel ganglioside-induced differentiation-associated protein 1 gene (BmGDAP1) was first cloned and sequenced from silkworm, Bombyx mori using rapid amplification of cDNA ends (RACE). The full-length cDNA of BmGDAP1 was 1514bp, consisting of a 91bp 5′ untranslated region (UTR), a 424bp 3′-UTR and a 999bp open reading frame (ORF). The ORF encoded a polypeptide of 332 amino acids, which possessed a thioredoxin (TRX)-like domain, a glutathione S-transferase-C (GST-C) family domain and a transmembrane segment. Furthermore, quantitative real-time PCR analysis revealed that BmGDAP1 transcripts were mainly presented in the tissues of hemocytes and midgut of silkworm, and its expression level was down-regulated in the hemocytes, while up-regulated in the midgut. Therefore, it could be concluded that BmGDAP1 plays an important role in the recognition and immune response of silkworm to BmCPV infection. [Copyright &y& Elsevier]

MicroRNAs (miRNAs) are small non-coding RNAs that function as novel gene expression regulators at the post-transcriptional level. Not with standing that the biogenesis and function of miRNAs are well-understood in eukaryotes, little is known about RNA virus-encoded miRNAs. Bombyx mori cypovirus (BmCPV) is a double-stranded RNA virus with a segmented genome that causes cytoplasmic polyhedrosis disease in silkworm larvae. To date, the interaction between BmCPV and silkworm remains largely unclear. 22 candidate BmCPV-encoded miRNAs were identified in this study through small RNA sequencing, stem-loop RT-PCR and qRT-PCR. Then, generation and function analyses were conducted on one of the candidate miRNAs, BmCPV-miR-1, in the BmN cells and the silkworm larvae by RNA interference, quantitative PCR, dual-luciferase assay. Our results revealed that BmCPV-miR-1 was encoded by BmCPV genome RNA rather than the degraded fragments of the viral genome. Its generation depended on Dicer-1 and might also be correlated with Dicer-2, Argonaute-1 and Argonaute-2. Moreover, BmCPV-miR-1 could suppress the expression of the target gene, B. mori inhibitor of nuclear factor kappa-B kinase subunit beta (BmIKKβ), via binding to the target mRNA 3′-untranslated region, which fine-tuned the host NF-κB signaling pathway and consequently enhanced viral replication. Our results provide new evidence supporting the hypothesis that RNA viruses could generate miRNAs to modulate antiviral host defense. [Display omitted] • At least 22 candidate BmCPV-encoded miRNAs were identified. • BmCPV-miR-1 was encoded by BmCPV and its biogenesis depended on Dicer-1. • BmCPV-miR-1 suppressed the target gene BmIKKβ by binding to its mRNA 3′-UTR. • BmCPV-miR-1 enhanced BmCPV proliferation through suppressing target gene BmIKKβ. • Results support the hypothesis that RNA viruses could generate functional miRNAs. [ABSTRACT FROM AUTHOR]

Abstract: MucK is a member of the major facilitator super family (MFS) and is within a subgroup involved in the uptake of organic acids. Here, we provide the first evidence that mucK is required for normal body color pattern in insect larvae. In the cts mutant strain of Bombyx mori (Linnaeus), the larval anal plates, prothoracic tergum, and the head are reddish brown, as opposed to the white color found in the wild type. Positional cloning of the cts gene was carried out and it was mapped within 90kb on the 16th chromosome. Two molecular markers, 182A4 and 242GA, were found co-segregated with the cts phenotype. Only one candidate gene in the region, BGIBMGA013242, which codes for a major facilitator super family protein named BmMucK, located between the two loci. Sequence analysis revealed that a ∼3kb deletion in the genome resulting in a 126bp deletion in the open reading frame (ORF) of BmmucK in the cts mutant. Fluorescence in situ hybridization (FISH) and quantitative reverse transcription PCR showed that BmmucK expression coincided with reddish brown pigmented regions in the cts mutant strain. BmmucK expression in the head and anal plates were markedly elevated at the molting stages. We performed RNA interference of the mucK homolog in Tribolium castaneum and observed brown coloration accompanied by lethality in ∼1/3 of the insects. The results suggest that MucK plays an important role in the pigmentation process of insect larvae. [Copyright &y& Elsevier]