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Abstract: Peroxiredoxins (Prxs) are believed to play an important role in insects for protection against the toxicity of reactive oxygen species (ROS). A gene encoding a novel 1-Cys Prx was firstly identified and characterized from an expressed sequence tag database (EST) in the lepidopteran insect, Bombyx mori. The 1-Cys Prx of B. mori (BmPrx) cDNA contained an open reading frame of 672 bp encoding a protein of 223 amino acid residues with calculated molecular mass of 25 kDa and included conserved cysteine residues signature motifs (PVCT) in the N-terminus amino acid. Sequence comparison showed that BmPrx shared 53 to 64% identity with other species 1-Cys proteins. RT-PCR revealed that the BmPrx transcripts were present in all tissues and developmental stages. The coding sequence was cloned and expressed as a 30-kDa protein in Escherichia coli. The purified enzyme acted as a catalyst in ferrithiocyanate system and protected supercoiled form of plasmid DNA from damage in metal-catalyzed oxidation (MCO) system in vitro. In addition, real-time PCR analysis indicated that significant rise of the transcripts level of BmPrx was induced by temperature stress including low and high temperature stimuli. [Copyright &y& Elsevier]

Dietary restriction (DR) leads to extended lifespan in many species ranging from yeasts to mammal, and it can also affect the immune system to some extent. Herein, we investigated whether DR can enhance the immunity of Bombyx mori suffering from acute pathogenic microorganism infection. The results showed that DR could accelerate the melanisation reaction, delay the early death in silkworms, meanwhile Staphylococcus aureus (SA) load was lower in the early stage of infection. Moreover, more immune-related genes were identified to be down-regulated in the DR group infected with SA compared with the ad libitum – fed (AL) group infected with SA through mRNA deep sequencing (RNAseq) and quantitation PCR. We speculate that rapid melanization may beneficial to the lower SA load and delay the time point of the early death, and the lower SA load may lead to many immune-related DEGs were down-regulated. These results may help us to understand the mechanisms by which DR affects the immune system in insects and other animals. [ABSTRACT FROM AUTHOR]

Abstract: A gene encoding Bombyx mori arginine kinase (BmAK) has been indentified differentially expressed in the midguts of Bombyx mori strain NB which is resistant to nucleopolyhedrovirus (BmNPV), strain 306 which is susceptible to NPV and a near isogenic line BC8 with similar genetic background to 306 but resistant to NPV by two-dimensional gel electrophoresis (2-DE). In this study, we characterized the expression profiles of BmAK using RT-PCR and real-time quantitative PCR. The expression level of BmAK fluctuated in various developing stage and various tissue. Remarkably, the expression level of BmAK increased more than 10-fold 24 hours post inoculation (h p.i.) of NPV in strain NB and BC8, while such increment was abraded in strain 306 although the basal expression level of BmAK in strain 306 was higher than that of strain NB and BC8. Western blotting analysis using polyclonal antibody against BmAK verified such observation, and immunofluoresence analysis indicated for the first time that BmAK was mainly located to the cytoplasm or some structures in cytoplasm. These findings suggest that arginine kinase is involved in the antiviral process of Bombyx mori larvae against NPV infection. [Copyright &y& Elsevier]