STEPN-UP · Stilbene and entomopathogenic nematodes: Unlocking the potential

Stilbene and entomopathogenic nematodes: Unlocking the potential

Bacteria frequently form intimate associations with a eukaryotic host where they may have critical roles in the development, behavior, and/or functions of their animal symbiont. While the underlying molecular mechanisms are poorly understood there is increasing evidence that the bacteria are sending signals to their host. The goal of this project was to understand the inter-kingdom signaling that occurs between a bacterium and its animal host using, as a model, the interaction between an entomopathogenic nematode (EPN) called Heterorhabditis and its symbiotic bacterium, Photorhabdus. The Heterorhabditis-Photorhabdus EPN complex has been exploited as a biological control agent for >20 years and various product formulations are currently available in the EU. Although the global biocontrol market (currently estimated at €200 million per annum) has seen significant market growth over the past 5-10 years the market for EPNs has been relatively flat . This stagnation is due in part to the relatively high costs associated with the production and storage of the product. The STEPN-UP project aimed to generate new knowledge on the Heterorhabditis-Photorhabdus EPN complex in order to enable future rationale-based approaches to improve EPN production for commercial exploitation to benefit the agri-food sector and the environment/society. EPNs are soil-dwelling organisms that utilize a bacterial symbiont to kill their insect targets . Photorhabdus plays a key role in the EPN life-cycle and is required to have 3 distinct functions during the life-cycle of the EPN complex: 1) Photorhbdus must kill the insect host; 2) Photorhabdus must convert the insect cadaver into a nutrient soup for nematode growth and development and 3) Photorhabdus must re-colonise a specialized free-living stage of the nematode (the infective juvenile) that emerges from the dead insect to find a new host . A key metabolite produced by the bacteria during this complex life-cycle is called ST and, importantly, ST is required for nematode growth and development. Therefore, the overall research objectives for STEPN-UP as listed in the application are: 1) to investigate the evolutionary history of ST synthesis proteins. 2) to determine the nematode response to ST. 3) to engineer the bacteria to produce increased levels of ST. Briefly this project showed that: 1) Proteins involved in the production of ST are unique in Photorhabdus. 2) The alarmone (p)ppGpp is essential for the full reproductive potential of the nematode. 3) The Cpx regulon in Photorhabdus is necessary to maintain its symbiotic relationship with Heterorhabditis.

Data: CORDIS, © European Union