Phytophthora Disrupts Plant Immunity by Manipulating Nitric Oxide Homeostasis Through GSNOR Inhibition.

Area of Science:

• Plant pathology
• Molecular plant-microbe interactions
• Redox signaling

Background:

• Nitric oxide (NO) is crucial for plant development and immunity, mediating responses via S-nitrosylation.
• Pathogen strategies to manipulate NO-dependent plant immunity are not fully understood.

Purpose of the Study:

• To investigate if Phytophthora capsici (P. capsici) hijacks NO-mediated signaling to subvert tomato immunity.
• To elucidate the role of S-nitrosoglutathione reductase (GSNOR) in plant defense against P. capsici.

Main Methods:

• Investigated GSNOR's role in tomato resistance to P. capsici.
• Analyzed the interaction between the P. capsici effector PcRD18 and GSNOR.
• Utilized structure analysis and site-directed mutagenesis to map interaction interfaces.
• Assessed the impact of GSNOR and PcRD18 mutations on NO homeostasis, ROS burst, and virulence.

Main Results:

• GSNOR positively regulates tomato resistance to P. capsici; mutations in GSNOR's active site impair its defense function.
• The P. capsici RxLR effector PcRD18 inhibits GSNOR activity and promotes its degradation, increasing cellular NO and S-nitrosylation.
• PcRD18 targets specific interfaces on GSNOR, and disrupting this interaction blocks PcRD18's virulence effects.
• Mutant GSNOR forms that resist PcRD18 binding enhance Phytophthora resistance.

Conclusions:

• P. capsici employs PcRD18 to hijack GSNOR, disrupting NO homeostasis and suppressing plant immunity.
• Targeting the PcRD18-GSNOR interaction interface offers a strategy for engineering enhanced crop disease resistance.