Arabidopsis thaliana methionine sulfoxide reductase B8 influences stress-induced cell death and effector-triggered immunity
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Reactive oxygen species (ROS) oxidize methionine to methionine sulfoxide (MetSO) and thereby inactivate proteins. Methionine sulfoxide reductase (MSR) enzyme converts MetSO back to the reduced form and thereby detoxifies the effect of ROS. Our results show that Arabidopsis thaliana MSR enzyme coding gene MSRB8 is required for effector-triggered immunity and containment of stress-induced cell death in Arabidopsis.
Plants activate pattern-triggered immunity (PTI), a basal defense, upon recognition of evolutionary conserved molecular patterns present in the pathogens. Pathogens release effector molecules to suppress PTI. Recognition of certain effector molecules activates a strong defense, known as effector-triggered immunity (ETI). ETI induces high-level accumulation of reactive oxygen species (ROS) and hypersensitive response (HR), a rapid programmed death of infected cells. ROS oxidize methionine to methionine sulfoxide (MetSO), rendering several proteins nonfunctional. The methionine sulfoxide reductase (MSR) enzyme converts MetSO back to the reduced form and thereby detoxifies the effect of ROS. Though a few plant MSR genes are known to provide tolerance against oxidative stress, their role in plant–pathogen interaction is not known. We report here that activation of cell death by avirulent pathogen or UV treatment induces expression of MSRB7 and MSRB8 genes. The T-DNA insertion mutant of MSRB8 exaggerates HR-associated and UV-induced cell death and accumulates a higher level of ROS than wild-type plants. The negative regulatory role of MSRB8 in HR is further supported by amiRNA and overexpression lines. Mutants and overexpression lines of MSRB8 are susceptible and resistant respectively, compared to the wild-type plants, against avirulent strains of Pseudomonas syringae pv. tomato DC3000 (Pst) carrying AvrRpt2, AvrB, or AvrPphB genes. However, the MSRB8 gene does not influence resistance against virulent Pst or P. syringae pv. maculicola (Psm) pathogens. Our results altogether suggest that MSRB8 function is required for ETI and containment of stress-induced cell death in Arabidopsis.
KeywordsArabidopsis Hypersensitive response Incompatible interaction MSRB7 MSRB8 Pseudomonas syringae
Cauliflower mosaic virus 35S
Hours post inoculation
Methionine sulfoxide reductase
Pseudomonas syringae pv. tomato
Pattern triggered immunity
Quantitative real-time PCR
RPM1 interacting protein 13
We thank Zeeshan Z. Banday for comments on the manuscript. We acknowledge Arabidopsis Biological Resource Center, Ohio State University, USA for the mutant seeds. This work is supported by financial assistance from DST projects (F. No.SERB/SR/SO/PS/150/2012). SR is a recipient of a Council for Scientific and Industrial Research (CSIR) fellowship.
SR performed the experiments, analyzed data, and wrote the manuscript. AKN conceptualized the project, designed the experiments, and wrote the manuscript.
Compliance with ethical standards
Conflict of interest
The authors have no conflict of interest to declare.
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