Phosphorylation-dependent control of an RNA granule-localized protein that fine-tunes defence gene expression at a post-transcriptional level.

Naheed Tabassum,Dierk Scheel,Benedikt Athmer,Wolfgang Hoehenwarter,Manaswita Baruah,Lennart Eschen‐Lippold,Luis D Maldonado‐Bonilla,Martina Brode,Justin Lee,Gerd Hause

doi:10.1111/tpj.14573

Naheed Tabassum, Dierk Scheel + Show 8 more

Open Access

PDF Available

https://doi.org/10.1111/tpj.14573

Copy DOI

Export

Save

Cite

Abstract
Highlights/Summary
Full-Text PDF
Similar Papers

Abstract

Listen

Mitogen-activated protein kinase (MAPK) cascades are key signalling modules of plant defence responses to pathogen-associated molecular patterns [PAMPs; e.g. the bacterial peptide flagellin (flg22)]. Tandem zinc finger protein 9 (TZF9) is a RNA-binding protein that is phosphorylated by two PAMP-responsive MAPKs, MPK3 and MPK6. We mapped the major phosphosites in TZF9 and showed their importance for controlling in vitro RNA-binding activity, in vivo flg22-induced rapid disappearance of TZF9-labelled processing body-like structures and TZF9 protein turnover. Microarray analysis showed a strong discordance between transcriptome (total mRNA) and translatome (polysome-associated mRNA) in the tzf9 mutant, with more mRNAs associated with ribosomes in the absence of TZF9. This suggests that TZF9 may sequester and inhibit the translation of subsets of mRNAs. Fittingly, TZF9 physically interacts with poly(A)-binding protein 2 (PAB2), a hallmark constituent of stress granules - sites for stress-induced translational stalling/arrest. TZF9 even promotes the assembly of stress granules in the absence of stress. Hence, MAPKs may control defence gene expression post-transcriptionally through release from translation arrest within TZF9-PAB2-containing RNA granules or by perturbing the function of PAB2 in translation control (e.g. in the mRNA closed-loop model of translation).

Highlights

Plants are sessile organisms and are constantly exposed to a variety of potential pathogens in their environment
We showed that the Arabidopsis tandem zinc finger 9 (TZF9) is a putative RNA-binding protein localised to processing bodies (PB) and is a phosphotarget of MPK3 and MPK6
We identified the major phosphorylated sites in Tandem zinc finger protein 9 (TZF9) and showed that flg22-induced protein destabilisation, reduction of TZF9-labelled PB structures and RNA-binding properties are dependent on the phosphosites

Summary

Introduction

Plants are sessile organisms and are constantly exposed to a variety of potential pathogens in their environment. To combat these invaders, plants have developed both preformed and inducible defence systems. The first-tier of inducible defence, known as pathogen-associated molecular pattern (PAMP)-triggered immunity (PTI), is activated through recognition of conserved microbial features called PAMPs via membrane-localised receptors. One of the central components of PTI includes phosphorylation-dependent activation of three-tiered mitogen-activated protein kinase (MAPK) cascades (Colcombet and Hirt, 2008). The MAPKKKs are serine or threonine kinases that phosphorylate downstream MKKs at conserved S/T-X3-5-S/T motifs. MKKs in turn phosphorylate MAPKs at threonine or tyrosine residues in their activation loop (Suarez-Rodriguez et al, 2010).

Results

Discussion

Conclusion