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Changes in PUB22 Ubiquitination Modes Triggered by MITOGEN-ACTIVATED PROTEIN KINASE3 Dampen the Immune Response

Giulia Furlan1,2, Hirofumi Nakagami3,4, Lennart Eschen-Lippold5

  • 1Independent Junior Research Group-Ubiquitination in Immunity, Leibniz Institute of Plant Biochemistry, Halle (Saale) 06120, Germany.

The Plant Cell
|March 11, 2017
PubMed

Insights

MITOGEN-ACTIVATED PROTEIN KINASE3 (MPK3) phosphorylates the E3 ubiquitin ligase PUB22, stabilizing it and dampening the plant immune response. This reveals a negative feedback loop regulating cellular signaling and homeostasis.

Area of Science:

  • Plant immunity
  • Molecular signaling
  • Posttranslational modifications

Background:

  • Posttranslational modifications like ubiquitination and phosphorylation are crucial for regulating cellular signaling.
  • Understanding negative feedback loops in cellular signaling is essential for maintaining homeostasis.
  • The role of MITOGEN-ACTIVATED PROTEIN KINASE3 (MPK3) in signaling activation is well-established, but its regulatory roles are less understood.

Purpose of the Study:

  • To elucidate the molecular mechanisms of negative feedback loops in plant immunity.
  • To investigate the role of MPK3 in regulating the E3 ubiquitin ligase PUB22.
  • To uncover how posttranslational modifications control immune response duration and intensity.

Main Methods:

  • Investigated the interaction between MPK3 and PUB22 in *Arabidopsis thaliana*.
  • Analyzed the effect of MPK3-mediated phosphorylation on PUB22 stability and oligomerization.
  • Studied the impact of PUB22 autoubiquitination on immune signaling.

Main Results:

  • MPK3 phosphorylates PUB22 at residues near its E2 docking domain.
  • Phosphorylation inhibits PUB22 oligomerization and subsequent autoubiquitination, leading to PUB22 stabilization.
  • Stabilized PUB22 effectively dampens the plant immune response, establishing a negative feedback loop.

Conclusions:

  • MPK3-mediated phosphorylation of PUB22 is a key regulatory mechanism that dampens plant immune responses.
  • Autoubiquitination of E3 ligases can serve as an in vivo self-regulatory mechanism.
  • This pathway highlights the intricate crosstalk between phosphorylation and ubiquitination in controlling signaling.

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