Related Experiment Video
Updated: Jun 20, 2025
Identification of Post-translational Modifications of Plant Protein Complexes
Published on: February 22, 2014
Comparative analysis on natural variants of fire blight resistance protein FB_MR5 indicates distinct effector
Haseong Kim1, Jieun Kim2, Minseon Kim3
1Plant Immunity Research Center, Seoul National University, Seoul 08826, Republic of Korea.
Abstract:
FB_MR5 is a nucleotide-binding domain and leucine-rich repeat protein identified from wild apple species Malus × robusta 5 conferring disease resistance to bacterial fire blight. FB_MR5 (hereafter MrMR5) recognizes the cysteine protease effector EaAvrRpt2 secreted from the causal agent of bacterial fire blight, Erwinia amylovora. We previously reported that MrMR5 is activated by the C-terminal cleavage product (ACP3) of Malus domestica RIN4 (MdRIN4) produced by EaAvrRpt2-directed proteolysis. We show that MbMR5 from a wild apple species Malus baccata shares 99.4% amino acid sequence identity with MrMR5. Surprisingly, transient expression of MbMR5 in Nicotiana benthamiana showed autoactivity in contrast to MrMR5. Domain swap and mutational analyses revealed that 1 amino acid polymorphism in the MbMR5 CC domain is critical in enhancing autoactivity. We further demonstrated that MrMR5 carrying 7 amino acid polymorphisms present in MbMR5 is not activated by MdRIN4 ACP3 but recognizes AvrRpt2 without MdRIN4 in N. benthamiana. Our findings indicate that naturally occurring polymorphisms of MR5 natural variants can confer its cell death-inducing activity and the effector recognition mechanism likely due to altered compatibility with RIN4.
Insights
Polymorphisms in the apple disease resistance protein FB_MR5 (MrMR5) alter its activity and effector recognition. Variations in MrMR5 influence its interaction with RIN4, impacting bacterial fire blight resistance.
Area of Science:
- Plant pathology
- Molecular biology
- Genetics
Background:
- Bacterial fire blight, caused by Erwinia amylovora, is a devastating disease in apple orchards.
- Nucleotide-binding domain and leucine-rich repeat (NLR) proteins confer disease resistance in plants.
- FB_MR5 (MrMR5) from Malus × robusta 5 recognizes the Erwinia amylovora effector EaAvrRpt2 and is activated by MdRIN4 cleavage products.
Purpose of the Study:
- To investigate the functional impact of polymorphisms in naturally occurring FB_MR5 variants.
- To elucidate the molecular basis for altered autoactivity and effector recognition in FB_MR5.
Main Methods:
- Comparative analysis of FB_MR5 (MrMR5) and MbMR5 from Malus baccata.
- Transient expression in Nicotiana benthamiana.
- Domain swap and mutational analyses.
- Investigating effector recognition with and without MdRIN4.
Main Results:
- MbMR5 exhibits autoactivity, unlike MrMR5, due to a single amino acid polymorphism in the CC domain.
- MrMR5 with MbMR5 polymorphisms recognizes AvrRpt2 independently of MdRIN4.
- Polymorphisms alter the interaction with RIN4, affecting cell death-inducing activity and effector recognition.
Conclusions:
- Naturally occurring polymorphisms in MR5 variants significantly influence its disease resistance function.
- Altered compatibility with RIN4 is a key mechanism underlying variations in MR5 activity and effector recognition.
- These findings provide insights into the evolution of NLR-mediated plant immunity.
More Related Videos
11:50Bacterial Leaf Infiltration Assay for Fine Characterization of Plant Defense Responses using the Arabidopsis thaliana-Pseudomonas syringae Pathosystem
Published on: October 1, 2015
08:57Native Polyacrylamide Gel Electrophoresis Immunoblot Analysis of Endogenous IRF5 Dimerization
Published on: October 6, 2019
