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Breakthrough in research on interaction between Bacillus thuringiensis and nematode from Microbial Pesticide Team


  (By Chen Ling) A paper entitled “Small RNA-mediated cry toxin silencing allows Bacillus thuringiensis to evade Caenorhabditis elegans avoidance behavioral defenses”, which revealed a novel strategy of sRNA-mediated regulation to aid pathogens in combating host avoidance behavioral defenses by using Caenorhabditis elegans and its bacterial pathogen Bacillus thuringiensis as a model, was published on Nucleic Acids Research,On October 23, 2017. The work was achieved by the microbial pesticide team of State Key Laboratory of Agricultural Microbiology in HZAU. A/Prof. Peng Donghai is the first author and Prof. Sun Ming is the corresponding author.

   Pathogen avoidance behavior protects animal hosts against microbial pathogens. Pathogens have evolved specific strategies during coevolution in response to such hosts’ defenses. However, the molecule mechanism of these strategies for combatting host avoidance behavioral defenses remain poorly understood. During the research process of Prof. Sun’s team, they noticed the B. thuringiensis strain YBT-1518, which encodes three nematicidal cry genes, is highly toxic to C. elegans. However, the most potent toxin, Cry5Ba, is silenced in this strain when YBT-1518 lives outside the host. With deeply studying, they found Cry5Ba silencing is due to the sRNA BtsR1, which binds to the RBS site of the cry5Ba gene via direct base pairing and inhibited Cry5Ba expression. Upon ingestion by C. elegans, Cry5Ba is expressed in vivo by strain YBT-1518. Cry5Ba silencing may allow B. thuringiensis to avoid nematode behavioral defenses and then express toxins once ingested to kill the host and gain a survival advantage. This study is the first article to report sRNA involved in the pathogenic adaptation to host avoidance behavioral defenses.

   This research is funded by the National Key R&D Program of China, the National Natural Science Foundation of China, the China 948 Program of Ministry of Agriculture, the Fundamental Research Funds for the Central Universities, and the Funding for open access charge: The National Key R&D Program of China.

   Actually, this is one of the outstanding work from the Sun’ s lab on interaction between B. thuringiensis and nematodes in past 2 years. Other work included presenting the viewpoint that nematode is the more important host of B. thuringiensis than insects and can be the disseminator and source of saprophytic nutrition (Trends Microbiol, 2015), discovering a B. thuringiensis two-domain protein Nel that can induce both PTI response in plant and necrosis in nematode (Environ Microbiol, 2015), revealing B. thuringiensis collagenase ColB can destroy the physical barrier of host and facilitate B. thuringiensis colonization in host (Environ Microbiol, 2016), illustrating a novel B. thuringiensis nematicidal protein Cry6Aa can target to C. elegans aspartic protease ASP-1 and induces cell necrosis of nematodes (PLoS Pathog, 2016 ), identifying the structure and biosynthetic gene cluster of a nematicidal small molecule substance TAA of B. thuringiensis (J Biol Chem, 2017), demonstrating the B. thuringiensis evolutionary strategy to adapt multi-host by comparing 130 B. thuringiensis genomes (mBio, 2017) and so on. These researches not only give new understandings to study the pesticidal mechanism of B. thuringiensis, but also supply a new strategy and gene resources for producing more efficient B. thuringiensis pesticide and cultivating novel pest-resistant trans-gene crop.

   Reviewed by Sunming


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