Abstract
The Toll pathway is one of the most important signaling pathways regulating insect innate immunity. Spatzle is a key protein that functions as a Toll receptor ligand to trigger Toll-dependent expression of immunity-related genes. In this study, a novel spatzle gene (ApSPZ) from the Chinese oak silkworm Antheraea pernyi was identified. The ApSPZ cDNA is 1065 nucleotides with an open reading frame (ORF) of 777 bp encoding a protein of 258 amino acids. The protein has an estimated molecular weight of 29.71 kDa and an isoelectric point (PI) of 8.53. ApSPZ is a nuclear and secretory protein with no conserved domains or membrane helices and shares 40% amino acid identity with SPZ from Manduca sexta. Phylogenetic analysis indicated that ApSPZ might be a new member of the Spatzle type 1 family, which belongs to the Spatzle superfamily. The expression patterns of several genes involved in the Toll pathway were examined at different developmental stages and various tissues in 5th instar larvae. The examined targets included A. pernyi spatzle, GNBP, MyD88, Tolloid, cactus and dorsalA. The RT-PCR results showed that these genes were predominantly expressed in immune-responsive fat body tissue, indicating that the genes play a crucial role in A. pernyi innate immunity. Moreover, A. pernyi infection with the fungus Nosema pernyi and the gram-positive bacterium Enterococcus pernyi, but not the gram-negative bacterium Escherichia coli, activated the Toll signaling pathway. These results represent the first study of the Toll pathway in A. pernyi, which provides insight into the A. pernyi innate immune system.
MeSH terms
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Amino Acid Sequence
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Animals
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Base Sequence
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Carrier Proteins / genetics
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Carrier Proteins / immunology
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Cloning, Molecular
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DNA, Complementary / genetics
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DNA, Complementary / immunology
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Enterococcus / pathogenicity
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Enterococcus / physiology
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Fat Body / immunology
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Fat Body / microbiology
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Gene Expression Regulation, Developmental
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Immunity, Innate
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Insect Proteins / genetics*
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Insect Proteins / immunology
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Isoelectric Point
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Larva / genetics*
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Larva / immunology
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Larva / microbiology
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Manduca / genetics
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Manduca / immunology
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Manduca / microbiology
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Molecular Weight
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Moths / genetics*
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Moths / immunology
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Moths / microbiology
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Myeloid Differentiation Factor 88 / genetics
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Myeloid Differentiation Factor 88 / immunology
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Nosema / pathogenicity
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Nosema / physiology
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Nuclear Proteins / genetics*
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Nuclear Proteins / immunology
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Open Reading Frames / immunology*
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Phosphoproteins / genetics
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Phosphoproteins / immunology
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Sequence Alignment
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Signal Transduction / genetics
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Signal Transduction / immunology*
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Toll-Like Receptors / genetics
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Toll-Like Receptors / immunology
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Tolloid-Like Metalloproteinases / genetics
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Tolloid-Like Metalloproteinases / immunology
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Transcription Factors / genetics
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Transcription Factors / immunology
Substances
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Carrier Proteins
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DNA, Complementary
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Insect Proteins
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Myeloid Differentiation Factor 88
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Nuclear Proteins
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Phosphoproteins
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Toll-Like Receptors
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Transcription Factors
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Tolloid-Like Metalloproteinases
Grants and funding
This work was partially supported by the National Modern Agriculture Industry Technology System Construction Project (Silkworm and Mulberry) and the Magnitude Science and Technology Projects of Liaoning Province to LQ; the Cultivation Plan for Youth Agricultural Science and Technology Innovative Talents of Liaoning Province (2014040) and the Scientific Research Project for the Education Department of Liaoning Province (L2014255) to YJ; and the Scientific Research Project for Education Department of Liaoning Province (L2015488) to YW. The funders had no role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript.