Natural genetic diversity in the potato resistance gene RB confers suppression avoidance from Phytophthora effector IPI-O4

Authors: Karki, Hari; ABDULLAH, SIDRAT - University Of Wisconsin; CHEN, YU - University Of Wisconsin; Halterman, Dennis

Submitted to: Molecular Plant-Microbe Interactions
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/6/2021
Publication Date: 5/10/2021
Citation: Karki, H.S., Abdullah, S., Chen, Y., Halterman, D.A. 2021. Natural genetic diversity in the potato resistance gene RB confers suppression avoidance from Phytophthora effector IPI-O4. Molecular Plant-Microbe Interactions. https://doi.org/10.1094/MPMI-11-20-0313-R.
DOI: https://doi.org/10.1094/MPMI-11-20-0313-R

Interpretive Summary: Microorganisms that cause plant diseases present a substantial burden to agriculture through yield losses due to plant stress, costs associated with disease control, and efforts to detect infections and limit disease epidemics. Plant breeders are interested in the identification and incorporation of simply inherited genes that confer robust resistance to diseases. These resistance (R) genes typically encode proteins that recognize the presence of very specific pathogen molecules, termed effectors, resulting in the activation of defense responses. However, certain effectors can directly suppress R proteins to allow the pathogen to elude recognition and cause disease. Using the potato late blight pathosystem, we previously identified a Phytophthora infestans effector that can suppress RB activity through direct interaction with the resistance protein. By mining natural genetic variation of RB from wild potato relatives, we identified specific amino acids within the coiled-coil region of the R protein that allow it to avoid suppression and maintain its ability to activate defense responses in both transient and stable transgenic expression systems.

Technical Abstract: RB is a potato gene that provides resistance to a broad spectrum of genotypes of the late blight pathogen Phytophthora infestans. RB belongs to the CC-NB-LRR (coiled-coil, nucleotide-binding, leucine-rich repeat) class of resistance (R) genes, a major component of the plant immune system. It directly interacts with Class I and II IPI-O effectors from P. infestans to initiate a hypersensitive resistance response, but this activity is suppressed in the presence of the Class III effector IPI-O4. Using natural genetic variation of RB within potato wild relatives, we identified two amino acids in the CC domain that alter interactions needed for suppression of resistance by IPI-O4. We have found that separate modification of these amino acids in RB can diminish or enhance the resistance capability of this protein against P. infestans in both Nicotiana benthamiana and potato. Our results demonstrate that increased knowledge of the molecular mechanisms that determine resistance activation and R protein suppression by effectors can be utilized to tailor-engineer genes with the potential to provide increased durability.