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10.03.2021

+++ News Ticker Science #76 +++ Plant Defense +++

Exocyst subunit Exo70B2 is linked to immune signaling and autophagy.

During the immune response, plants synthesize various proteins including plasma membrane-localized receptors and molecules, which are secreted to the extracellular space. Therefore, activation of the secretory pathway is key for plant defense. As a part of this pathway, the exocyst protein complex tethers secretory vesicles to the inner side of the plasma membrane before membrane fusion and exocytosis take place. Scientists from the IPB together with colleagues from Freiburg, Bayreuth and Japan now succeeded in shedding more light on the molecular details of how the exocyst is regulated in coordination with the immune response.

First, the team of researchers could show that in Arabidopsis thaliana, Exo70B2 behaves as a bona fide exocyst subunit. Next, through treatment with a salicylic acid analog or immune response elicitor flg22, they could induce Exo70B2 recruitment into the vacuole. Transport into the vacuole was autophagy-dependent and likely mediated through interaction of Exo70B2 with AUTOPHAGY-RELATEDPROTEIN 8 (ATG8). Furthermore, Exo70B2 interacted with and was phosphorylated by the kinase MPK3. The results indicated that phosphorylation may control ATG8 interaction and increase vacuolar degradation of Exo70B2.

The researchers postulate a molecular mechanism by which phosphorylation diverts Exo70B2 from the secretory into the autophagy pathway for its degradation, to dampen secretory activity. Thus, Exo70B2 seems to act as a hub by coupling the secretory machinery with immune signaling and autophagy.

Original publication:
Carla Brillada, Ooi-Kock Teh, Franck Anicet Ditengou, Chil-Woo Lee, Till Klecker, Bushra Saeed, Giulia Furlan, Marco Zietz, Gerd Hause, Lennart Eschen-Lippold, Wolfgang Hoehenwarter, Justin Lee, Thomas Ott, Marco Trujillo. Exocyst subunit Exo70B2 is linked to immune signaling and autophagy, The Plant Cell, 2020; koaa022, doi.org/10.1093/plcell/koaa022

 

 

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