Physical and functional interaction of the Arabidopsis K+ channel AKT2 and phosphatase AtPP2CA. Plant Cell
The AKT2 K(+) channel is endowed with unique functional properties, being the only weak inward rectifier characterized to date in Arabidopsis. The gene is expressed widely, mainly in the phloem but also at lower levels in leaf epiderm, mesophyll, and guard cells. The AKT2 mRNA level is upregulated by abscisic acid. By screening a two-hybrid cDNA library, we isolated a protein phosphatase 2C (AtPP2CA) involved in abscisic acid signaling as a putative partner of AKT2. We further confirmed the interaction by in vitro binding studies. The expression of AtPP2CA (beta-glucuronidase reporter gene) displayed a pattern largely overlapping that of AKT2 and was upregulated by abscisic acid. Coexpression of AtPP2CA with AKT2 in COS cells and Xenopus laevis oocytes was found to induce both an inhibition of the AKT2 current and an increase of the channel inward rectification. Site-directed mutagenesis and pharmacological analysis revealed that this functional interaction involves AtPP2CA phosphatase activity. Regulation of AKT2 activity by AtPP2CA in planta could allow the control of K(+) transport and membrane polarization during stress situations.
[Show abstract] [Hide abstract] ABSTRACT: Background The type-2C protein phosphatases (PP2Cs), negatively regulating ABA responses and MAPK cascade pathways, play important roles in stress signal transduction in plants. Brachypodium distachyon is a new model plant for exploring the functional genomics of temperate grasses, cereals and biofuel crops. To date, genome-wide identification and analysis of the PP2C gene family in B. distachyon have not been investigated. Results In this study, 86 PP2C genes in B. distachyon were identified. Domain-based analyses of PP2C proteins showed that they all contained the phosphatase domains featured as 11 conserved signature motifs. Although not all phosphatase domains of BdPP2C members included all 11 motifs, tertiary structure analysis showed that four residues contributing to magnesium/manganese ions (Mg2+/Mn2+) coordination were conserved, except for two noncanonical members. The analysis of their chromosomal localizations showed that most of the BdPP2C genes were located within the low CpG density region. Phylogenetic tree and synteny blocks analyses among B. distachyon, Arabidopsis thaliana and Oryza sativa revealed that all PP2C members from the three species can be phylogenetically categorized into 13 subgroups (A–M) and BdPP2Cs were evolutionarily more closely related to OsPP2Cs than to AtPP2Cs. Segmental duplications contributed particularly to the expansion of the BdPP2C gene family and all duplicated BdPP2Cs evolved mainly from purifying selection. Real-time quantitative reverse transcription PCR (qRT-PCR) analysis showed that BdPP2Cs were broadly expressed in disparate tissues. We also found that almost all members displayed up-regulation in response to abiotic stresses such as cold, heat, PEG and NaCl treatments, but down-regulation to biotic stresses such as Ph14, Guy11 and F0968 infection. Conclusions In the present study, a comprehensive analysis of genome-wide identification and characterization of protein domains, phylogenetic relationship, gene and protein structure, chromosome location and expression pattern of the PP2C gene family was carried out for the first time in a new model monocot, i.e., B. distachyon. Our results provide a reference for genome-wide identification of the PP2C gene family of other species and also provide a foundation for future functional research on PP2C genes in B. distachyon. Electronic supplementary material The online version of this article (doi:10.1186/s12864-016-2526-4) contains supplementary material, which is available to authorized users.0Comments 0Citations
- "It has been demonstrated that subgroup A PP2Cs in Arabidopsis, foxtail millet and rice are transcriptionally upregulated upon exogenous ABA treatment or stress conditions that stimulate ABA biosynthesis [23, 24, 42, 43]. Seven members of subgroup A AtPP2Cs have been characterized as negative regulators of ABA responses in ABA-mediated physiological processes444546474849. In B. distachyon, subgroup A BdPP2Cs includes eight members (BdPP2C27, BdPP2C34, BdPP2C36, BdPP2C37, BdPP2C44, BdPP2C46, BdPP2C47 and BdPP2C75). "
[Show abstract] [Hide abstract] ABSTRACT: Plants are sessile organisms and have multiple tolerance mechanisms which allow them to adapt to the environmental stresses to which they may be exposed. Key to a plant’s tolerance of abiotic stresses is the ability to rapidly detect stress and activate the appropriate stress response mechanism. The calcineurin B-like (CBL) and CBL-interacting protein kinase (CIPK) signalling pathway is a flexible Ca2+ signalling network which allows a plant to fine tune its response to stress, via both pre- and post-translational mechanisms. Genes encoding CBLs and CIPKs have now been identified in a variety of plant species. Plants have been found to have large gene families of CBLs and CIPKs, each encoding proteins with specific upstream and downstream targets, thus providing the flexibility required to allow a plant to adapt to a variety of stresses. Characterisation of CBL and CIPK mutants have shown them to be important for a plant to survive cold, drought, heat, salinity and low nutrient stresses. Many CBLs and CIPKs have been shown to be involved in the transport of ions through a plant, either limiting the supply of toxic ions to certain tissues or maximising the uptake of beneficial nutrients from the soil. This review will provide an update into the current knowledge of CBL and CIPK interactions and their role in ion transport during abiotic stress.0Comments 4Citations
- "A de/phosphorylation network is thought to regulate the functional switch from influx to efflux, with AtPP2CA dephosphorylation found to repress the ability of AKT2 to move K ? out of the cell (Chérel et al. 2002; Sandmann et al. 2011). While AtCIPK6 has been shown not to phosphorylate AKT2, interaction of the AtCBL4–CIPK6 complex with AKT2 is necessary to activate AKT2's K ? "
[Show abstract] [Hide abstract] ABSTRACT: The phytohormone abscisic acid (ABA) plays an essential role in the abiotic stress response and tolerance of plants, especially during water-related stresses. Thus, ABA is also known as a plant stress hormone. In response to drought and/or salinity stresses, the expression of many ABA-responsive genes is16.1 induced. Several transcription factors and their corresponding DNA target sequences have been identified to control this biological response on the molecular level. Drought stress can directly induce ABA biosynthesis, transportation, and release from its storage form. The activity of ion channels, located on the guard cell membrane, is modulated by drought and/or salinity stresses to regulate stomata movement, which can be simulated by treatment with ABA. In this chapter, we focus on the ABA regulation of drought and salt responses in plants, examining gene expression, stress signaling, and ion homeostasis under these stresses.0Comments 0Citations
- " and play important roles in K + homeostasis (Gaymard et al. 1998; Lebaudy et al. 2010; Marten et al. 1999; Pilot et al. 2001; Xicluna et al. 2007). ABA up-regulated the expression of AKT2 and decreased the expression of SKOR under drought and high salinity stresses (Deeken et al. 2002; Gaymard et al. 1998; Lacombe et al. 2000; Marten et al. 1999). Cherel et al. (2002) provided evidence that AtPP2CA, a protein phosphatase involved in ABA signaling, interacts with AKT2 and is considered a partner of AKT2. It was reported that SRK2E/OST1/SnRK2.6, one of the subclass β SnRK2 family members, global regulators of ABA signaling, inhibits the activity of KAT1, an inward K + channel, through phosphorylation o"