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Mol Plant. 2018 Nov 30. pii: S1674-2052(18)30365-4. doi: 10.1016/j.molp.2018.11.011. [Epub ahead of print]

A Plant Immune Receptor Degraded by Selective Autophagy.

Author information

1
Department of Plant Pathology, University of Nebraska, Lincoln, NE 68588-0722, USA; Center for Plant Science Innovation, University of Nebraska, Lincoln, NE 68588-0660, USA.
2
Center for Plant Science Innovation, University of Nebraska, Lincoln, NE 68588-0660, USA; Department of Biochemistry, University of Nebraska, Lincoln, NE 68588-0664, USA.
3
Center for Biotechnology, University of Nebraska, Lincoln, NE 68588-0665, USA.
4
Center for Plant Science Innovation, University of Nebraska, Lincoln, NE 68588-0660, USA.
5
Center for Plant Science Innovation, University of Nebraska, Lincoln, NE 68588-0660, USA; Department of Biochemistry, University of Nebraska, Lincoln, NE 68588-0664, USA. Electronic address: jalfano2@unl.edu.
6
Department of Plant Pathology, University of Nebraska, Lincoln, NE 68588-0722, USA; Center for Plant Science Innovation, University of Nebraska, Lincoln, NE 68588-0660, USA. Electronic address: jalfano2@unl.edu.

Abstract

Plants recycle non-activated immune receptors to maintain a functional immune system. The Arabidopsis immune receptor kinase FLAGELLIN-SENSING 2 (FLS2) recognizes bacterial flagellin. Arabidopsis orosomucoid (ORM) proteins are negative regulators of sphingolipid biosynthesis, but the mechanism by which they do this is not well understood. Here, we provide evidence that ORM proteins act as selective autophagy receptors to degrade FLS2. Arabidopsis plants over-expressing ORM1 or ORM2 lack or have greatly diminished FLS2 levels, lack FLS2 signaling, and are more susceptible to the bacterial pathogen Pseudomonas syringae. On the other hand, Arabidopsis ORM1/2 RNA-silenced plants and CRISPR orm1 or orm2 mutants have enhanced FLS2 levels and enhanced FLS2 signaling and are more resistant to P. syringae. ORM proteins interact with FLS2 and the autophagy-related protein ATG8. FLS2 abundance returns to wild type levels in plants over-expressing ORM1/2 and defective in autophagy. Moreover, ORM1/2 derivatives that do not interact with ATG8 restore FLS2 to wild type levels in Arabidopsis plants over-expressing ORM1 or ORM2. These findings implicate selective autophagy in the maintenance of a plant immune receptor and suggest a broader role for ORM proteins beyond sphingolipid metabolic regulation.

PMID:
30508598
DOI:
10.1016/j.molp.2018.11.011

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