Abstract

Pathogen Resistance in Plants

Full Description

A basic pattern of resistance to pathogens in plants involves a "gene for gene" response where gene products are expressed by a plant in response to the binding of a particular protein ligand secreted by a pathogenic organism. These ligands, encoded by the pathogen's avirulence (avr) genes, are thought to bind to the plant's receptor-like kinases (RLKs) present on the surface of plant cells. This binding event triggers the transduction of a signaling cascade pathway within the plant cell, and the resulting cascade leads to the expression of resistance genes whose peptide products target the specific pathogen, and possibly induce a secondary broad-spectrum resistance mechanism known as systemic acquired resistance (SAR).

While numerous RLKs and SAR-associated genes have been characterized, only one RLK, called Xa21, confers disease resistance to rice. Specifically, the rice Xa21 gene confers resistance against avirulent strains of Xanthomonas oryzae (Xoo), the organism that is responsible for bacterial leaf blight.

A University of California, Davis researcher and her associates have made a number of potentially significant inventions that relate to the Xa21 signaling mechanism and to SAR in rice, including:

• the identification and characterization of three rice proteins that bind to the Xa21 kinase domain, six Xoo genes that are required for avr-Xa21 activity, and a number of rice and maize RLKs that are homologous to Xa21;
• the engineering of chimeric receptors, including elements of the Xa21 kinase, to provide novel methods for inducing and regulating RLK function;
• the identification and characterization of rice SAR proteins, including rice homologues of NPR1 (a SAR regulatory protein from Arabidopsis), rice transcription factors that bind NPR1, and a rice proline-rich NPR1-interactor that negatively regulates the resistance response; and
• the genetic manipulation of NPR1 and the rice homolog NH1 (using the Xa21 system) to enhance the SAR response.

Suggested uses

Because of the economic importance of rice and the magnitude of disease-related losses, Xa21 is potentially important for the engineering of broad-spectrum resistance into rice and other important crop plants. Specifically, these applications may include the following:

• the use of avr genes to trigger the RLK-mediated downstream response for enhancing resistance to diverse pathogens and to achieve better understanding of downstream signaling events;
• the use of engineered chimeric receptors to screen for avr ligands, to assay downstream functions regulated by RLK, or to create transgenic plants resistant to normally virulent pathogens;
• the use of RLK genes to provide novel mechanisms for controlling disease resistance in rice, maize, and possibly other crops; and
• the use of rice SAR genes to engineer broad-spectrum disease resistance in rice and possibly in other economically-significant monocots.

Patent Status

Inventors

• Chern, Maw Shenq
• Ronald, Pamela C.

Other Information

Contact

Randi L. Jenkins / rljenkins@ucdavis.edu / tel: View Phone Number. Please reference Tech ID #11201.

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