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Research Project: Using Genetic Approaches to Reduce Crop Losses in Rice Due to Biotic and Abiotic Stress

Location: Dale Bumpers National Rice Research Center

Title: The rice blast resistance gene Ptr encodes an atypical protein required for broad spectrum disease resistance

Author
item ZHAO, HAIJUN - Orise Fellow
item WANG, XUEYAN - University Of Arkansas
item Jia, Yulin
item MINKENBERG, BASTIAN - Pennsylvania State University
item WHEATLEY, MATTHEW - Pennsylvania State University
item FAN, JIANGBO - The Ohio State University
item Jia, Melissa
item FAMOSO, ADAM - Louisiana State University
item Edwards, Jeremy
item WAMISHE, YESHI - University Of Arkansas
item VALENT, BARBARA - Kansas State University
item WANG, GUO-LIANG - The Ohio State University
item YANG, YINONG - Pennsylvania State University

Submitted to: Nature Communications
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/16/2018
Publication Date: 5/23/2018
Citation: Zhao, H., Wang, X., Jia, Y., Minkenberg, B., Wheatley, M., Fan, J., Jia, M.H., Famoso, A., Edwards, J., Wamishe, Y., Valent, B., Wang, G., Yang, Y. 2018. The rice blast resistance gene Ptr encodes an atypical protein required for broad spectrum disease resistance. Nature Communications. https://doi.org:10.1038/s41467-018-04369-4.
DOI: https://doi.org/10.1038/s41467-018-04369-4

Interpretive Summary: Blast disease of rice caused by the fungus Magnaporthe oryzae is the most damaging rice disease worldwide. Major resistance (R) genes are effective in controlling this disease. Most of the cloned blast R genes are predicted to encode proteins with nucleotide binding site- leucine rich repeats (NLR), and the molecular bases of disease resistance mediated by R genes are still largely unclear. In the present study, we identified a novel R gene, Ptr, encoding a protein with an Armadillo repeat that is physically close to another effectively deployed NLR blast R gene, Pi-ta. Ptr was delimited within 63 kilobases with two DNA markers, W195 and Z14, and predicted to produce two proteins with 864 and 905 amino acids, respectively. The Ptr protein was localized in the cytoplasm of plant cells. Deletion of two base pairs in the protein coding region with Ptr by fast neutrons in a mutant of rice cultivar, M2354, created a truncated protein resulting in blast susceptibility. CRISPR-Cas9 was used to further validate the resistant function of Ptr at Pennsylvania State University. Rice germplasm with Ptr and Pi-ta confer resistance to a wide range of US races/isolates of rice blast fungus. The cloning of Ptr will help to elucidate the complex molecular mechanism of blast resistance. Linked DNA markers are useful for monitoring the introgression of Ptr for improving blast resistance via a marker assisted breeding strategy.

Technical Abstract: Plant resistance (R) genes typically encode proteins with nucleotide binding site-leucine rich repeat (NLR) domains. We identified a novel, broad-spectrum rice blast R gene, Ptr, encoding a non-NLR protein with four Armadillo repeats. Ptr was originally identified by fast neutron mutagenesis as a gene required for function of both NLR gene Pi-ta and the associated, uncharacterized R gene Pi-ta2. Ptr is expressed constitutively and encodes two predicted proteins that are mainly localized in the cytoplasm. A two base pair deletion within the Ptr protein coding region in the fast neutron-generated mutant line M2354 created a truncated protein, resulting in susceptibility to the blast pathogen M. oryzae. Targeted mutation of Ptr in a resistant cultivar using CRISPR/Cas9 led to blast susceptibility, further confirming its resistance function. The cloning of Ptr reveals an entirely new class of plant R genes and provides new insights into the complexity of plant immunity.