Abstract
Entomopathogenic bacteria Serratia marcescens is widely used as an environmentally friendly biocontrol agent against various pests, including Spodoptera exigua. Understanding the immune defense mechanism of S. exigua through comparative proteomic analysis can identify the key proteins expressed in response to the microbial infection. Here, we employed the as isobaric tags for relative and absolute quantification (iTRAQ) technique to investigate the effects of S. marcescens on the proteomic expression of S. exigua. Based on the molecular functional analysis, the differentially expressed proteins (DEPs) were mainly involved in the binding process and catalytic activities. Further bioinformatics analysis revealed important DEPs that played a crucial role in innate immunity of S. exigua with recognition (C-type lectin), melanization (propanol oxidase 3, serine protease, Serine-type carboxypeptidase activity, clip domain serine protease 4), antimicrobial activity (lysozyme, lysozyme-like, gloverin, cecropin B), detoxification (acetyl-CoA C-acetyltransferase, 3-dehydroecdysone 3-alpha-reductase, glucuronosyltransferase, glutathione S-transferase) and others. The Quantitative real-time PCR (qRT-PCR) results further indicated the significant upregulation of the immune-related genes in Spodoptera exigua following S. marcescens infection. To the best of our knowledge, this is the first iTRAQ based study to characterize S. marcescens mediated proteomic changes in S. exigua and identified important immune-related DEPs. The results of this study will provide an essential resource for understanding the host-pathogen interactions and the development of novel microbial biopesticides against various pests.
Highlights
Friendly entomopathogenic microbes used as an alternative to chemicals for controlling different pests
The experimental larvae were inoculated with a different bacterial concentration to characterize the interaction between S. exigua and S. marcescens
The present study identified the upregulation of propanol oxidase (PPO), an essential immune protein associated with melanization, and intermediates formed during this process might allow the host to kill the pathogen
Summary
Friendly entomopathogenic microbes used as an alternative to chemicals for controlling different pests. There has been a sustained research activity in different entomopathogenic microbes and their roles for agricultural pest controls S. marcescens is a gramnegative entomopathogenic bacterium, belongs to the family Enterobacteriaceae and is commonly found in different insects (Pineda-Castellanos et al, 2015; Bidari et al, 2018). The effectiveness and stabilities of microbial insecticides were hindered due to the development of resistance by the insects (Cory and Franklin, 2012). Understanding the host defense mechanisms is essential to the development of effective entomopathogen-based biopesticides to manage pests in different environments
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