Pathogen derived effectors and their use in enhancing plant resistance to pathogens, insect pests and freezing stress

Method for producing transgenic plants that are resistant to at least one pathogen and one insect pest are provided. Plants expressing a pathogen-derived effector that are resistant to at least one pathogen, at least one insect pest, and freezing stress are provided. Genes and gene sequences comprising pathogen-derived effectors chosen as to not trigger the hypersensitive response and to be capable of enhancing gene silencing on a given plant are also provided, as well as plants, plant parts, plant cells, seeds, and non-human host cells expressing such genes.

The Invention discloses the finding that certain phytobacterial type III effector proteins with silencing enhancer activity, which may provide protection against biotic and/or abiotic plant stresses. Also provided are sequences, constructs and methodology for obtaining plants comprising a phytobacterial type III effector protein, which may have resistance to at least one insect and at least one type of plant stress.

Type III effectors (T3SE) are virulence proteins of many gram negative bacteria
that are injected into plant host cells by the Type III injectisome, a mutliprotein channel generally found in pathogenic bacteria . In plant-bacterium pathosystems, T3SEs suppress innate plant immunity and may induce effector-triggered immunity if they are recognized by protein receptors such as those coded by plant resistance genes (R genes). Many T3SEs are multifunctional proteins, with distinct cellular functions associated with different structural domains. Aside from triggering resistance in plant genotypes that have functionally complementary receptors, the Inventors discovered that the silencing-enhancing effectors engage the RNA-mediated gene silencing mechanism even in plants where effector-receptor gene recognition is not operative.
More specifically, the Inventors discovered that some T3SEs from Pseudomonas syringae enhance the sense-posttranscriptional gene silencing (s-PGTS) mechanisms in plants in which HR is not elicited following effector gene delivery via the Agrobacterium transient expression system. In so doing, Applicant determined that a small subset of the effectors tested from various pathovars of Pseudomonas syringae have such activity, while the majority do not appear to do so.
Truncation and mutation studies verified that the plant receptor recognition domains of are not involved in enhancing silencing. Furthermore, the Inventors demonstrates that one such effector gene can provide effective protection against infestation by certain insects in transgenic lines of the model plant Nicotiana benthamiana. Taken together, the inventors determined that this or other bacterial effector proteins with silencing enhancer activity may find utility in crop protection. In particular, this protection is very effective against phloem-feeding insects such as whiteflies. Phloem-feeding insects transmit many harmful viruses to crop plants. Therefore, and contrasted with known methods of breeding plant resistance to pathogens and insects, the invention utilizes new proteins, endowed with unique functions. Protection against other types of insect pests is currently under investigation. Additionally, the inventors discovered that the particular effector gene also provides effective protection against the crown gall disease caused by Agrobacterium tumefaciens, and may enhance the ability of plants to recover after exposure to subfreezing temperatures. The Patent describes some 25 homologues of this particular effector protein that are found in fully or partially sequenced phytobacterial genomes.

Attached files:
Reduced colonization of N benthamiana by WHITEFLIES.pdf

US 201,206,799 issued 2012-06-28
US 2,011,060,567 issued 2012-05-16

Type of Offer: Sale or Licensing

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