A novel domain in the protein kinase SOS2 mediates interaction with the protein phosphatase 2C ABI2. Proc Natl Acad Sci U S A

Department of Plant Sciences, University of Arizona, Tucson, AZ 85721, USA.
Proceedings of the National Academy of Sciences (Impact Factor: 9.67). 10/2003; 100(20):11771-6. DOI: 10.1073/pnas.2034853100
Source: PubMed


SOS2 (salt overly sensitive 2) is a serine/threonine protein kinase required for salt tolerance in Arabidopsis thaliana. In this study, we identified the protein phosphatase 2C ABI2 (abscisic acid-insensitive 2) as a SOS2-interacting protein. Deletion analysis led to the discovery of a novel protein domain of 37 amino acid residues, designated as the protein phosphatase interaction (PPI) motif, of SOS2 that is necessary and sufficient for interaction with ABI2. The PPI motif is conserved in protein kinases of the SOS2 family (i.e., protein kinase S, PKS) and in the DNA damage repair and replication block checkpoint kinase, Chk1, from various organisms including humans. Mutations in the conserved amino acid residues in the PPI motif abolish the interaction of SOS2 with ABI2. We also identified a protein kinase interaction domain in ABI2 and examined the interaction specificity between PKS and the ABI phosphatases. We found that some PKSs interact strongly with ABI2 whereas others interact preferentially with ABI1. The interaction between SOS2 and ABI2 was disrupted by the abi2-1 mutation, which causes increased tolerance to salt shock and abscisic acid insensitivity in plants. Our results establish the PPI motif and the protein kinase interaction domain as novel protein interaction domains that mediate the binding between the SOS2 family of protein kinases and the ABI1/2 family of protein phosphatases.

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    • "In the C-terminal regulatory domain, the conserved NAF or FISL motif is responsible for interacting with Ca 2+ -bound CBLs, leading to the activation of the targeting CIPKs (Albrecht et al., 2001; Guo et al., 2001). In addition, the protein-phosphatase interaction (PPI) domain within the C-terminus of CIPKs can also target specific members of the protein phosphatase 2C (PP2C; Ohta et al., 2003). "
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    ABSTRACT: Cassava is an important food and potential biofuel crop that is tolerant to multiple abiotic stressors. The mechanisms underlying these tolerances are currently less known. CBL-interacting protein kinases (CIPKs) have been shown to play crucial roles in plant developmental processes, hormone signaling transduction, and in the response to abiotic stress. However, no data is currently available about the CPK family in cassava. In this study, a total of 25 CIPK genes were identified from cassava genome based on our previous genome sequencing data. Phylogenetic analysis suggested that 25 MeCIPKs could be classified into four subfamilies, which was supported by exon-intron organizations and the architectures of conserved protein motifs. Transcriptomic analysis of a wild subspecies and two cultivated varieties showed that most MeCIPKs had different expression patterns between wild subspecies and cultivatars in different tissues or in response to drought stress. Some orthologous genes involved in CIPK interaction networks were identified between Arabidopsis and cassava. The interaction networks and co-expression patterns of these orthologous genes revealed that the crucial pathways controlled by CIPK networks may be involved in the differential response to drought stress in different accessions of cassava. Nine MeCIPK genes were selected to investigate their transcriptional response to various stimuli and the results showed the comprehensive response of the tested MeCIPK genes to osmotic, salt, cold, oxidative stressors, and ABA signaling. The identification and expression analysis of CIPK family suggested that CIPK genes are important components of development and multiple signal transduction pathways in cassava. The findings of this study will help lay a foundation for the functional characterization of the CIPK gene family and provide an improved understanding of abiotic stress responses and signaling transduction in cassava.
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    • "SOS1 protein is the direct target of SOS signaling pathway, and it is regulated through protein phosphorylation by the alternative SOS2/ SOS3 and SOS2/CBL10 protein kinase complexes (Qiu et al. 2002; Quintero et al. 2002, 2011; Quan et al. 2007). ABI2 is the negative regulatory of this pathway, through the inhibition of SOS2 kinase activity or the activity of SOS2 targets, suggesting a cross talk between the ABA pathway and SOS pathway (Ohta et al. 2003). "
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    ABSTRACT: Salinity is a major environmental stress that limits agriculture production. Hence, it is essential to produce salt-tolerant crops for sustaining food production. Understanding the molecular basis of salt-stress signaling and tolerance mechanisms is essential for breeding and genetic engineering of salt tolerance in crop plants. Plant adaptation or tolerance to salinity stress involves complex physiological traits, metabolic pathways, and molecular or gene networks. In many plants, the salt tolerance is associated with the ability to exclude sodium from the shoot, to prevent its accumulation in pho-tosynthetic tissues. Salinity stress involves changes in various physiological and metabolic processes, depending on severity and duration of the stress, and ultimately inhibits crop production. In this chapter, we mainly discuss about the effect of salinity on plants and tolerance mechanisms that permit the plants to withstand stress.
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    • "Elevated CO2-induced salt stress tolerance | 7401 unknown. However, exposure to a range of abiotic stresses, including salt stress, generally induces ABA biosynthesis and accumulation (Tuteja, 2007), which regulates SOS2 gene expression (Ohta et al., 2003) and activates MAPKs such as MPK6 via RBOH-dependent H 2 O 2 production (Kovtun et al., 2000; Samuel et al., 2000; Lu et al., 2002; Zhang et al., 2006; Zhang et al., 2007; Xing et al., 2008). The C-terminal region of the Arabidopsis SOS1 gene is phosphorylated by MPK6 under high NaCl conditions (Yu et al., 2010). "
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