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

Abstract

Summary 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).

BcMF30a and BcMF30c, Two Novel Non-Tandem CCCH Zinc-Finger Proteins, Function in Pollen Development and Pollen Germination in Brassica campestris ssp. chinensis

“…Furthermore, the overexpression of these genes usually can enhance abiotic stress tolerance [ 17 , 23 , 27 , 28 ]. AtTZF9 is the only known RR-TZF gene that regulates immunity in Arabidopsis [ 29 , 30 ].…”

Dynamics and Functions of Stress Granules and Processing Bodies in Plants

“…In response to flagellin (flg22) treatment, MPK3/MPK6 phosphorylated another p-body component, tandem zinc finger protein 9 (TZF9), and led to a decrease of TZF9-associated p-bodies in Arabidopsis protoplasts [ 43 ] ( Figure 2 d). A comparison of the transcriptome and translatome between the wild type and tzf9 mutant revealed that TZF9 can regulate flg22-dependent gene expression at the translation level [ 43 ]. Together with data from Yu et al [ 42 ], the treatment of flg22 induced the disassembly of p-bodies in both cases.…”

“…( c ) Yu et al (2019) demonstrated that the treatment of flg22 triggered the disassembly of DCP1-associated p-bodies and differential mRNA decay in Arabidopsis protoplasts [ 42 ]. ( d ) The treatment of flg22 led to the decrease of TZF9-containing granules and the release of translation repression in Arabidopsis protoplasts [ 43 ]. The spherical dark-shade clusters in the background of the upper panel of (d) are chloroplasts (Ch).…”

Reshaping of theArabidopsis thalianaproteome landscape and co-regulation of proteins in development and immunity

“…Several post-transcriptional/translational mechanisms controlling protein abundance have just recently been uncovered in plant immunity (Meteignier et al, 2017;Xu et al, 2017;Tabassum et al, 2019). Therefore we investigated reshaping of the proteome in the steady state shift from growth to pattern triggered immunity (PTI).…”