93-kDa twin-domain serine protease inhibitor (Serpin) has a regulatory function on the beetle Toll proteolytic signaling cascade.
ABSTRACT Serpins are protease inhibitors that play essential roles in the down-regulation of extracellular proteolytic cascades. The core serpin domain is highly conserved, and typical serpins are encoded with a molecular size of 35-50 kDa. Here, we describe a novel 93-kDa protein that contains two complete, tandemly arrayed serpin domains. This twin serpin, SPN93, was isolated from the larval hemolymph of the large beetle Tenebrio molitor. The N-terminal serpin domain of SPN93 forms a covalent complex with the Spätzle-processing enzyme, a terminal serine protease of the Toll signaling cascade, whereas the C-terminal serpin domain of SPN93 forms complexes with a modular serine protease and the Spätzle-processing enzyme-activating enzyme, which are two different enzymes of the cascade. Consequently, SPN93 inhibited β-1,3-glucan-mediated Toll proteolytic cascade activation in an in vitro system. Site-specific proteolysis of SPN93 at the N-terminal serpin domain was observed after activation of the Toll proteolytic cascade in vivo, and down-regulation of SPN93 by RNAi sensitized β-1,3-glucan-mediated larval death. Therefore, SPN93 is the first serpin that contains twin tandemly arrayed and functionally active serpin domains that have a regulatory role in the larval Toll proteolytic signaling cascade.
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ABSTRACT: Insects with complex life-cycles should optimize age and size at maturity during larval development. When inhabiting seasonal environments, organisms have limited reproductive periods and face fundamental decisions: individuals that reach maturity late in season have to either reproduce at a small size or increase their growth rates. Increasing growth rates is costly in insects because of higher juvenile mortality, decreased adult survival or increased susceptibility to parasitism by bacteria and viruses via compromised immune function. Environmental changes such as seasonality can also alter the quantitative genetic architecture. Here, we explore the quantitative genetics of life history and immunity traits under two experimentally induced seasonal environments in the cricket Gryllus bimaculatus. Seasonality affected the life history but not the immune phenotypes. Individuals under decreasing day length developed slower and grew to a bigger size. We found ample additive genetic variance and heritability for components of immunity (haemocyte densities, proPhenoloxidase activity, resistance against Serratia marcescens), and for the life history traits, age and size at maturity. Despite genetic covariance among traits, the structure of G was inconsistent with genetically based trade-off between life history and immune traits (for example, a strong positive genetic correlation between growth rate and haemocyte density was estimated). However, conditional evolvabilities support the idea that genetic covariance structure limits the capacity of individual traits to evolve independently. We found no evidence for G × E interactions arising from the experimentally induced seasonality.Heredity 12/2011; 108(5):569-76. DOI:10.1038/hdy.2011.125 · 3.80 Impact Factor
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ABSTRACT: Understanding the evolutionary ecology of immune responses to persistent infection could provide fundamental insight into temporal dynamics or interactive mechanisms that could be co-opted for antibiotic treatment regimes. Additionally, identification of novel molecules involved in these processes could provide novel compounds for biotechnological development. The beetle Tenebrio molitor displays a high level of induced antimicrobial activity coincident with persistent immuno-resistant Staphylococcus aureus, and is the first invertebrate model for persistent infection. Here we present expressed sequence tags (ESTs) detected by suppression-subtraction hybridization of Tenebrio larvae after infection with S. aureus. Amongst others, we identified mRNAs coding for various oxidative enzymes and two antimicrobial peptides. These ESTs provide a foundation for mechanistic study of Tenebrio's immune system.Journal of insect physiology 10/2012; 58(12). DOI:10.1016/j.jinsphys.2012.09.009 · 2.50 Impact Factor
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ABSTRACT: Tenebrio molitor has been seriously investigated as a model insect in elucidating Toll signaling pathway and related regulators of innate immunity. However, little is known with regards to the genomic information in T. molitor. In an attempt towards exploiting the rich transcriptomics data that would offer further insights into the study on insect immunity through potential screening of immune-related genes in the model insect, we constructed a cDNA library (library titer = 5.0 × 105pfu/ml) of T. molitor larvae and analyzed expressed sequence tag (EST) sequences from 1056 clones. The base calling and quality check of obtained chromatogram files were performed by using the Phred program (trim_alt 0.05 (P-score > 20). After removal of vector and 100 bp and less sequences, 1023 sequences were generated having an average insert size of 792 bp, including 160 clusters, 164 contigs and 387 singletons through clustering and assembling process using the TGI Clustering Tools (TGICL) package. The unique EST sequences were searched against the NCBI nr database by local BLAST (blastx, E < e−5) with 940 sequences showing significant hits. Subsequently, KOG (clusters of orthologous groups for eukaryotic complete genomes) analysis was conducted (blastx, E < e−10) towards prediction of transcriptomal functions, leading to the categorization of 638 genes. The majority of genes belonged to Z category (cytoskeleton-related genes), R category (general function prediction), and C category (energy production and conversion related genes). These basic EST datasets and their bioinformatics analysis will be helpful in investigating the biological mechanism and molecular pathway related genes involved in innate immunity mechanisms of T. molitor.Entomological Research 01/2013; 43(3):162-170. DOI:10.1111/1748-5967.12019 · 0.33 Impact Factor