D3279: Utility of plant elicitor peptides and rhizobacterial treatments to activate host plant defenses

Plant elicitor peptides are endogenous signals generated in response to mechanical damage, pathogen infection, and insect attack that activate a broad array of defensive pathways in plants. Treating soybean (Glycine max) seeds with a plant elicitor peptide from this species (GmPep3) can induce defense gene expression and reduce infection by root knot nematodes (Meloidogyne incognita) and soybean cyst nematodes (Heterodera glycines), suggesting that exogenous peptide treatments can to some extent immunize plants against herbivory. Here, we explore the utility of a common rhizobacterium, Bacillus subtilis, as a vector for delivery of peptides to plant roots. We have engineered B. subtilis to express GmPEP3 and applied it as a seed treatment, and are assessing the persistence of this rhizobacteria on roots and the outcomes of this treatment on subsequent nematode infection. Because certain strains of B. subtilis have plant growth-promoting effects, we are also assessing the impacts of rhizobacterial treatments with and without peptide expression on root and shoot growth. Because the impacts of both plant elicitor peptides and rhizobacteria are systemic and involve broad-spectrum defenses, our results may have relevance to other herbivores as well as plant-parasitic nematodes.