Arabidopsis G-protein interactome reveals connections to cell wall carbohydrates and morphogenesis

Botanical Institute, University of Cologne, Cologne, Germany.
Molecular Systems Biology 09/2011; 7(1). DOI: 10.1038/msb.2011.66
Source: PubMed


The heterotrimeric G-protein complex is minimally composed of Gα, Gβ, and Gγ subunits. In the classic scenario, the G-protein complex is the nexus in signaling from the plasma membrane, where the heterotrimeric G-protein associates with heptahelical G-protein-coupled receptors (GPCRs), to cytoplasmic target proteins called effectors. Although a number of effectors are known in metazoans and fungi, none of these are predicted to exist in their canonical forms in plants. To identify ab initio plant G-protein effectors and scaffold proteins, we screened a set of proteins from the G-protein complex using two-hybrid complementation in yeast. After deep and exhaustive interrogation, we detected 544 interactions between 434 proteins, of which 68 highly interconnected proteins form the core G-protein interactome. Within this core, over half of the interactions comprising two-thirds of the nodes were retested and validated as genuine in planta. Co-expression analysis in combination with phenotyping of loss-of-function mutations in a set of core interactome genes revealed a novel role for G-proteins in regulating cell wall modification.

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Available from: Yashwanti Mudgil, Apr 13, 2014
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    • "Approximately four-to five-week old tobacco leaves were infected with Agrobacterium tumifaciens harboring pCL113-WNK1, WNK8, WNK10 or P31 (At3G01290, a negative control) and pCL112-RACK1A, RACK1B or RACK1C to express split nYFP-and cYFP-tagged proteins. BiFC was performed as described previously (Klopffleisch et al., 2011) with a few modifications. An internal transformation control (mitochondrial marker; mCherry-mt-rk) was used to confirm infiltration of multiple plasmids (p19 gene silencing suppressor, mt-rk and two BiFC halves). "
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    ABSTRACT: Receptor of activated C kinase 1 (RACK1) is a versatile scaffold protein that binds to numerous proteins to regulate diverse cellular pathways in mammals. In Arabidopsis, RACK1 has been shown to regulate plant hormone signaling, stress responses and multiple processes of growth and development. However, little is known about the molecular mechanism underlying these regulations. Here, we show that an atypical serine/threonine protein kinase, WITH NO LYSINE KINASE 8 (WNK8), phosphorylates RACK1. WNK8 physically interacted with and phosphorylated RACK1 proteins at two residues, Ser122 (S122) and Thr162 (T162). Genetic epistasis analysis of rack1 wnk8 double mutants indicated that RACK1 acts downstream of WNK8 in the glucose responsiveness and flowering pathways. The phosphorylation-dead form, RACK1AS122A/T162A, but not the phosphomimetic form, RACK1AS122D/T162E, rescued the rack1a null mutant, implying that phosphorylation at Ser122 and Thr162 negatively regulates RACK1A function. The transcript of RACK1AS122D/T162E accumulated at similar levels as that of RACK1S122A/T162A. However, while the steady-state level of the RACK1AS122A/T162A protein was similar to wild-type RACK1A protein, the RACK1AS122D/T162E protein was nearly undetectable, suggesting that phosphorylation affects the stability of RACK1A proteins. Taken together, these results suggest that RACK1 is phosphorylated by WNK8 and that phosphorylation negatively regulates RACK1 function by influencing its protein stability. Copyright © 2014, American Society of Plant Biologists.
    Plant physiology 12/2014; DOI:10.1104/pp.114.247460 · 6.84 Impact Factor
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    • "Although several defense genes are constitutively upregulated in the ser1 and ser2 mutants, the precise molecular basis of their resistance has not yet been fully elucidated and the SER genes have not been characterized yet (Sánchez-Rodríguez et al., 2009). Arabidopsis mutants in the Gβ and Gγ1/γ2 subunits of the heterotrimeric G protein (i.e., agb1 single and agg1 agg2 double mutants, respectively) also have a reduced content of xylose in their cell walls and are hypersusceptible to the necrotrophic fungi P. cucumerina and Alternaria brassicicola, the biotrophic bacterium P. syringae and the vascular fungus Fusarium oxysporum (Table 1; Llorente et al., 2005; Trusov et al., 2010; Klopffleisch et al., 2011; Delgado-Cerezo et al., 2012; Liu et al., 2013; Lorek et al., 2013; Torres et al., 2013). Interestingly, the reduced resistance of agb1 single and agg1 agg2 double mutants was found to be independent of defense pathways required for resistance to these pathogens, such as those regulated by abscisic acid, salicylic acid, jasmonic acid and ethylene, and those that regulate the biosynthesis of tryptophan-derived metabolites (Delgado-Cerezo et al., 2012; Lorek et al., 2013; Torres et al., 2013). "
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    ABSTRACT: Plant resistance to pathogens relies on a complex network of constitutive and inducible defensive barriers. The plant cell wall is one of the barriers that pathogens need to overcome to successfully colonize plant tissues. The traditional view of the plant cell wall as a passive barrier has evolved to a concept that considers the wall as a dynamic structure that regulates both constitutive and inducible defense mechanisms, and as a source of signaling molecules that trigger immune responses. The secondary cell walls of plants also represent a carbon-neutral feedstock (lignocellulosic biomass) for the production of biofuels and biomaterials. Therefore, engineering plants with improved secondary cell wall characteristics is an interesting strategy to ease the processing of lignocellulosic biomass in the biorefinery. However, modification of the integrity of the cell wall by impairment of proteins required for its biosynthesis or remodeling may impact the plants resistance to pathogens. This review summarizes our understanding of the role of the plant cell wall in pathogen resistance with a focus on the contribution of lignin to this biological process.
    Frontiers in Plant Science 08/2014; 5:358. DOI:10.3389/fpls.2014.00358 · 3.95 Impact Factor
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    • "FIP1 (GSTU20) At1g28200 FIN219 interacting protein 1 Y2H, RC, AC Chen et al. (2007) JAR1/FIN219 At2g46370 Y2H, RC, PCA Wang et al. (2011) OPR3 (At2g06050) AGD12 At4g21160 ARF GAP domain 12 Y2H Braun et al. (2011) Coilin At1g13030 Y2H Braun et al. (2011) LOX2 (At3g45140) NDL1 At5g56750 N-MYC down regulated-like 1 Y2H Klopffleisch et al. (2011) EIF4E At4g18040 Eukaryotic translation initiation factor 4E Y2H, Co-IP, AC, RC Freire et al. (2000) LOX3 ( "
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    Journal of Experimental Botany 05/2014; 65(11). DOI:10.1093/jxb/eru230 · 5.53 Impact Factor
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