Abstract
Microsporidia are obligate intracellular, eukaryotic, spore-forming parasites. The environmentally resistant spores, which harbor a rigid cell wall, are critical for their survival outside their host cells and host-to-host transmission. The spore wall comprises two major layers: the exospore and the endospore. In Nosema bombycis, five spore wall proteins have been identified which contain two endosporal proteins (SWP25 and SWP30) and three exosporal proteins (NbSWP5, SWP26 and SWP32). In the current study, we identiï¬ed a novel endosporal protein NbSWP12 with calculated molecular mass of 25.56 kDa and pI of 6.69 using SDS-PAGE and MALDI-TOF MS technique. Followed by gene cloning and protein expression, polyclonal antibody production, indirect immunofluorescence antibody test, and immunoelectron microscopy analysis, the results indicate that this protein is localized to the endospore and has no obvious enhancement on adherence to host cells. The characterization of this novel spore wall protein from N. bombycis may facilitate our further investigation of the relationship between N. bombycis and its host, Bombyx mori. Key words: Microsporidia, Nosema bombycis, Spore wall protein, NbSWP12.
Highlights
Microsporidia, which are unicellular eukaryotes and obligate intracellular parasites, have long been recognized as pathogenic agents in sericulture, apiculture, and mammals (Wittner, 1999)
Microsporidia were previously divided into primitive eukaryotes, more and more molecular evidences based on the recent phylogenetic analyses of rDNA sequences, conserved proteins and the complete genome sequences of microsporidia Encephalitozoon cuniculi have demonstrated that these organisms are phylogenetically related to the fungi with remnant mitochondrial organelles (Hirt et al, 1999; Keeling et al, 2000; Fabienne et al, 2004; James et al, 2006; Goldberg et al, 2008; Lee et al, 2008)
The band for protein NbSWP12 with calculated molecular mass of 25.56 kDa and pI of 6.69 was excised and analyzed by MALDI-TOF-MS. It matched a 228-amino acid protein (Table 1) which was correspondent with that previously named as NbSWP12 under GenBank
Summary
Microsporidia, which are unicellular eukaryotes and obligate intracellular parasites, have long been recognized as pathogenic agents in sericulture, apiculture, and mammals (Wittner, 1999). The identified microsporidia have approximately 160 genera and 1300 described species (Corradi et al, 2008). At least 13 species are reported to infect humans (Dider et al, 2008), and five microsporidian genera have been found to infect the silkworm Bombyx mori (Bhat et al, 2009). As the causative agent of silkworm pebrine (Naegli, 1857), ravaged the silkworm industry of Europe, especially in Italy and France during the mid-19th century.
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