Plant TRAF Proteins Regulate NLR Immune Receptor Turnover

Area of Science:

• Plant immunity
• Molecular adaptors
• E3 ubiquitin ligase complexes

Background:

• Tumor necrosis factor receptor-associated factor (TRAF) proteins are key regulators of immunity and stress responses in animals.
• While plant TRAF-domain proteins show diversity, their functions remain largely unknown.
• Nucleotide-binding domain and leucine-rich repeat-containing (NLR) proteins are crucial plant immune receptors.

Purpose of the Study:

• To investigate the roles of plant TRAF proteins in regulating NLR immune receptors.
• To identify novel components involved in plant immune receptor turnover and homeostasis.

Main Methods:

• Gene identification and characterization of MUSE13 and MUSE14.
• Analysis of mutant phenotypes related to pathogen resistance and autoimmunity.
• Protein association studies using co-immunoprecipitation in planta.
• Investigating the impact of gene expression levels on NLR receptor abundance and activity.

Main Results:

• Identified two redundant TRAF proteins, MUSE13 and MUSE14, involved in NLR turnover.
• Loss of MUSE13 and MUSE14 results in increased pathogen resistance, NLR accumulation, and autoimmunity.
• MUSE13 overexpression leads to decreased NLR levels and activity.
• MUSE13 interacts with NLRs (SNC1, RPS2) and the E3 ubiquitin ligase SCF(CPR1).

Conclusions:

• MUSE13 and MUSE14 function redundantly to regulate NLR immune receptor stability.
• These TRAF proteins likely form a plant-specific complex (TRAFasome) with E3 ligases.
• This complex modulates NLR ubiquitination and degradation, maintaining immune receptor homeostasis.