|ZHAO, HAIJUN - Orise Fellow|
|WANT, XUEYAN - University Of Arkansas|
|LIU, YAN - University Of Arkansas|
Submitted to: American Phytopathological Society Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 7/1/2020
Publication Date: 8/3/2020
Citation: Jia, Y., Zhao, H., Want, X., Jia, M.H., Liu, Y., Box, H.N. 2020. Structural and functional characterization of an atypical rice blast resistance gene Ptr. American Phytopathological Society Annual Meeting.
Technical Abstract: Rice blast disease caused by the fungus, Magnaporthe oryzae, is one of the most damaging rice diseases worldwide. Effective resistance (R) genes and fungicides have been used to manage blast with limited success due to frequent genetic changes of the fungus. In the present study, we characterized a new type of disease resistance genes, Ptr, in rice. The Ptr gene, from a blast resistant tropical japonica rice variety Katy, was map-based cloned with the help of fast neutron mutagenesis and CRISPR-CAS9. The rice variety with Ptr is resistant to all known blast races in the US except for the races, IE1k and IB33. The Ptr gene has 4 exons and 3 introns encoding two predicted protein isoforms with 864 and 905 amino acids each carrying 4 armadillo repeats, but lacking a U box implying that the Ptr protein is an atypical E3 ligase. The absence of polyubiquitination signals at the Ptr protein in vitro suggests that Ptr does not have E3 ligase activity. Black hull weedy red rice, RR20, is resistant to IB33 and the R gene was mapped at the Ptr locus. There were two amino acid alterations of the Ptr protein in RR20 when compared with that of the susceptible mapping parent, Dee-Gee-Woo-Gen, and one of the two is also different when compared with that of Katy. These findings suggest that a single amino acid change of the Ptr protein in RR20 may determine pathogen signal recognition specificity. Ptr in rice varieties was found to be induced by blast pathogen and abiotic stresses including chilling, heat, drought and salt. Enhanced blast resistance of three rice germplasm lines carrying Ptr, SC272, SC324, SC353, after chilling was observed under greenhouse conditions. Progress on investigating the roles of Ptr in stress tolerance of selected rice germplasm will be presented.