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

Haijun Zhao,Melissa H Jia,Yinong Yang,Yeshi Wamishe,Guo-Liang Wang,Bastian Minkenberg,Jiangbo Fan,Xueyan Wang,Yulin Jia,Matthew Wheatley,Adam Famoso,Jeremy D Edwards,Barbara Valent

doi:10.1038/s41467-018-04369-4

Abstract

Plant resistance genes typically encode proteins with nucleotide binding site-leucine rich repeat (NLR) domains. Here we show that Ptr is an atypical resistance gene encoding a protein with four Armadillo repeats. Ptr is required for broad-spectrum blast resistance mediated by the NLR R gene Pi-ta and by the associated R gene Pi-ta2. Ptr is expressed constitutively and encodes two isoforms that are mainly localized in the cytoplasm. A two base pair deletion within the Ptr coding region in the fast neutron-generated mutant line M2354 creates a truncated protein, resulting in susceptibility to M. oryzae. Targeted mutation of Ptr in a resistant cultivar using CRISPR/Cas9 leads to blast susceptibility, further confirming its resistance function. The cloning of Ptr may aid in the development of broad spectrum blast resistant rice.

Highlights

Plant resistance genes typically encode proteins with nucleotide binding site-leucine rich repeat (NLR) domains
We find that a two base pair deletion within the Ptr protein coding region in the mutant line M2354 produces a truncated protein rendering susceptibility to M. oryzae
Five single nucleotide polymorphisms (SNPs) resulting in nonsynonymous mutations and one 12 bp deletion resulting in a four- amino acid deletion defines the functional region of Ptr in the fourth exon (Supplementary Table 1)

Summary

Introduction

Plant resistance genes typically encode proteins with nucleotide binding site-leucine rich repeat (NLR) domains. The second tier of plant defense is the effectortriggered immunity (ETI) mediated by plant resistance (R) genes, most of which encode cytoplasmic proteins with nucleotide binding site-leucine-rich repeat (NLR) domains[1]. In the United States, the tropical japonica cultivar Katy has been widely used in breeding programs as a source of the Pi-ta resistance complex which includes three R genes, Pi-ta, Pi-ta[2], and Ptr, in a region of suppressed recombination[6,7,8] This complex was introgressed from the variety Tetep and has been shown to be effective in preventing infections by a wide range of M. oryzae strains in the US over two decades[7,8]. Our genetic analysis suggests that Ptr, a non-NLR protein, functions in broad-spectrum blast resistance independent of Pi-ta, providing a strategy for developing blast resistance rice cultivars

Methods

Results

Conclusion