Exploiting breakdown in nonhost effector-target interactions to boost host disease resistance.

Area of Science:

• Plant Pathology
• Molecular Plant-Microbe Interactions
• Plant Immunity

Background:

• Nonhost resistance (NHR) provides broad-spectrum immunity against most microbes but its molecular basis is unclear.
• Pathogen effectors are virulence factors that manipulate host plants, and their failure to do so in nonhosts may underlie NHR.

Purpose of the Study:

• To investigate if the failure of pathogen effectors to manipulate nonhost plants contributes to NHR.
• To identify conserved effector-target interactions between host and nonhost plants.

Main Methods:

• Yeast two-hybrid (Y2H) screens were used to identify putative target proteins for Phytophthora infestans RxLR effectors in potato.
• Candidate orthologues (cAtOrths) in Arabidopsis were identified and screened for interaction with RxLR effectors from P. infestans and Hyaloperonospora arabidopsidis.
• The Arabidopsis orthologue AtPUB33 was expressed in potato and Nicotiana benthamiana to assess its effect on P. infestans colonization.

Main Results:

• Few P. infestans effector-target interactions were conserved between potato and Arabidopsis orthologues.
• An enrichment of H. arabidopsidis effectors interacting with Arabidopsis orthologues was observed.
• Expression of AtPUB33 significantly reduced P. infestans colonization in both potato and N. benthamiana.

Conclusions:

• The failure of pathogen effectors to interact with and manipulate target proteins in distantly related nonhost plants contributes to NHR.
• Transferring nonhost effector target orthologues to host plants represents a potential strategy for enhancing disease resistance.