# Exploring the Role of the Processing Body in Plant Abiotic Stress Response
## 4 P-Body and Plant Stress Responses
### Response of P-Body to Drought and Salt Stress  
In plants, the P-Body responds to drought or salt stress through modulating 5\({}^{\prime}\)\(\rightarrow\)3\({}^{\prime}\) mRNA degradation. Under drought or salt stress, transcripts undergo a deadenylation reaction catalyzed by poly(A)-specific ribonuclease (PARN) in _Arabidopsis_[10]. In P-Bodies, the deadenylated transcripts are decapped by the decapping complex consisting of DCP1, DCP2, DCP5, VCS, etc. [10, 22, 23]. When the _Arabidopsis_ seed was dehydrated for 15 min, MPK6 is activated and phosphorylates the Ser237 of the DCP1 protein. Phospho-DCP1 protein is preferentially associated with the RGG domain of DCP5 protein and promotes the interaction of the FDF domain of DCP5 with DCP2 protein to form the P-Body. And then the mRNA decapping was facilitated in the P-Body [23, 55]. Moreover, the VCS protein acts as a scaffold protein to facilitate the aggregation of the P-Body. This occurs by binding the components of the P-Body proteins together, such as interacting with the DCP1 protein through the N-terminal region and with the DCP2 protein through the C-terminal region in _Arabidopsis_[10, 15]. The decapped mRNA produced by the decapping complex is subsequently degraded by 5\({}^{\prime}\)\(\rightarrow\)3\({}^{\prime}\) exoribonuclease _At_XRN4 [10]. Similarly, the subclass I protein kinases SnRK2 proteins could phosphorylate VCS protein in the early stages under osmotic stress conditions. Phosphorylated VCS not only participates in 5\({}^{\prime}\)-3\({}^{\prime}\) mRNA degradation but also promotes the accumulation of transcripts that respond to drought stress [15, 56]. After 5 h of dehydration treatment, compared to the wild-type, the expression levels of 376 genes increased significantly in mutants lacking SnRK2 protein, while 519 genes decreased significantly [56]. Most of these up-/downregulated genes were genes whose expression was suppressed by drought and genes that favored drought resistance, respectively [56]. The results suggest that protein kinases modify the conformation of conserved P-Body proteins through phosphorylation, promoting their interaction and assembly into complexes with mRNA degradation functions, known as P-Body. Apart from the complex composed of conserved proteins, CCCH-zinc finger proteins, which are dynamic proteins of the P-Body, also modulate plant growth and stress response by regulating the expression of drought-related genes at both transcriptional and post-transcriptional levels [57]. Under drought or salt conditions, members of the zinc finger protein family-OsTZF7, OsC3H10, OsTZF1, and AtTZF1 can traffic between the nucleus and P-Body/stress granules [25, 26, 27, 57]. The overexpression of OsTZF7, OsC3H10, or OsTZF1 in Oryza sativa and AtTZF1 in Arabidopsis results in significantly lower rates of water loss compared to wild-type plants after drought treatment, while the RNAi-mediated knockdown of these genes in Oryza sativa or Arabidopsis leads to slightly higher rates of water loss [25, 26, 27, 58]. RNA-seq and DNA microarray analyses of OE and WT plants showed that transcripts of genes associated with dehydration response, such as metallothioneein, ferritin, and dehydrins are significantly upregulated in OE lines [25, 26, 27, 58]. OsTZF7, OsTZF1, and other TZF proteins have also been reported to be involved in salt stress response [25, 27]. When the wild-type, OsTZF1-OX, and OsTZF1-RNAi Oryza sativa seedlings were subjected to 250 mM NaCl for 3 days, the survival ratios of OsTZF1-OX and control plants (WT) were over 65% and 33%, respectively, and the survival ratios of OsTZF1-OX was twice of that of the wild-type [27]. In contrast, 19% to 21% of the OsTZF1-RNAi plants survived, which is lower than that of the control lines [27]. In addition, DNA microarray analysis revealed that the transcripts of salt stress tolerance genes are upregulated significantly in OsTZF1-OX transgenic seedlings, such as RD22, YSL6, allene oxide synthase, etc. [27].