Specificity of RCN1-Mediated Protein Phosphatase 2A Regulation in Meristem Organization and Stress Response in Roots

Blakeslee, Joshua J.; Zhou, Hongwei; Heath, Jeffrey T.; Skottke, Kyle R.; Rodriguez, Jorge A.; Liu, Su-Yang; DeLong, Alison

doi:10.1104/pp.107.112995

Cited by 75 publications

(96 citation statements)

References 65 publications

(104 reference statements)

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“…Homology searches identified four Arabidopsis SAPS domain-like proteins (SAL1-4), which share 45 to 72% sequence similarity. The Arabidopsis Information Resource public database shows that SAL proteins are located in either the plasma membrane or the endomembrane system (http:// www.Arabidopsis.org/), which is similar to the subcellular localization of PP2AAs (Michniewicz et al, 2007;Blakeslee et al, 2008) and the membrane localization of FyPPs (see Supplemental Figure 9 online). We examined protein-protein interactions between these subunits in yeast and plants.…”

Section: Fypp1 and Fypp3 Directly Dephosphorylate Pin Proteinsmentioning

confidence: 52%

“…To further test the genetic interactions between FyPPs and RCN1 and SAL1, we introduced the f1 f3 mutation into the rcn1-6 (Blakeslee et al, 2008) and sal1 mutant backgrounds. Both rcn1 f1 f3 and sal1 f1 f3 triple mutants had shorter roots than their parental lines ( Figure 8A).…”

Section: Pp6 Acts Antagonistically With Pid To Regulate Plant Developmentioning

confidence: 99%

“…The T-DNA insertion mutants of fypp1 (or f1, CS874166), fypp3 (or f3, CS877364), rcn1-6 (SALK_059903; Blakeslee et al, 2008), sal1 (SALK_035181), sal2 (C3806869), sal3 (SALK_039664), sal4 (SALK_144179), and pid-14 (SALK_049736) were ordered from the Salk Institute. The T-DNA insertions of f1, f3, rcn1-6, sal1, sal2, sal3, sal4, and pid-14 were confirmed by PCR/ sequencing; the homozygotes were identified by genotyping and further confirmed by RT-PCR expression analysis.…”

Section: Plant Materials and Growth Conditionsmentioning

confidence: 99%

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A PP6-Type Phosphatase Holoenzyme Directly Regulates PIN Phosphorylation and Auxin Efflux in Arabidopsis

et al. 2012

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The directional transport of the phytohormone auxin depends on the phosphorylation status and polar localization of PIN-FORMED (PIN) auxin efflux proteins. While PINIOD (PID) kinase is directly involved in the phosphorylation of PIN proteins, the phosphatase holoenzyme complexes that dephosphorylate PIN proteins remain elusive. Here, we demonstrate that mutations simultaneously disrupting the function of Arabidopsis thaliana FyPP1 (for Phytochrome-associated serine/threonine protein phosphatase1) and FyPP3, two homologous genes encoding the catalytic subunits of protein phosphatase6 (PP6), cause elevated accumulation of phosphorylated PIN proteins, correlating with a basal-to-apical shift in subcellular PIN localization. The changes in PIN polarity result in increased root basipetal auxin transport and severe defects, including shorter roots, fewer lateral roots, defective columella cells, root meristem collapse, abnormal cotyledons (small, cup-shaped, or fused cotyledons), and altered leaf venation. Our molecular, biochemical, and genetic data support the notion that FyPP1/3, SAL (for SAPS DOMAIN-LIKE), and PP2AA proteins (RCN1 [for ROOTS CURL IN NAPHTHYLPHTHALAMIC ACID1] or PP2AA1, PP2AA2, and PP2AA3) physically interact to form a novel PP6-type heterotrimeric holoenzyme complex. We also show that FyPP1/3, SAL, and PP2AA interact with a subset of PIN proteins and that for SAL the strength of the interaction depends on the PIN phosphorylation status. Thus, an Arabidopsis PP6-type phosphatase holoenzyme acts antagonistically with PID to direct auxin transport polarity and plant development by directly regulating PIN phosphorylation. INTRODUCTIONAuxin is a fundamental plant hormone that regulates almost every aspect of plant growth and development, including embryogenesis, organogenesis, apical dominance, tissue regeneration, and tropisms (reviewed in Bennett and Scheres, 2010;Grunewald and Friml, 2010;Peris et al., 2010). Auxin is transported from its sites of biosynthesis to its sites of action by a polarized auxin transport system. Molecular genetic studies in Arabidopsis thaliana have lead to the identification and functional characterization of several key players of the polarized auxin transport system, such as the auxin uptake carriers AUXIN RESISTANT1/LIKE AUX1 (AUX1/ LAX) (Swarup et al., 2008), the auxin efflux carriers, including PIN-FORMED (PIN) family proteins Chen et al., 1998;Müller et al., 1998;Friml et al., 2002;Petrásek et al., 2006), and P-glycoprotein auxin transporters ABCB1 (for ATP BINDING CASSETTE PROTEIN SUBFAMILY B1), ABCB4, and ABCB19 (Terasaka et al., 2005;Bouchard et al., 2006;Blakeslee et al., 2007;Lin and Wang, 2005). PIN proteins are asymmetrically targeted to the plant cell plasma membranes, resulting in distinct polar subcellular localization in a given tissue. For example, PIN1 is localized in the basal (rootward, lower) plasma membrane of stele cells and xylem cells in the vascular system, which is required for long-distance auxin flow from the shoot apex to the root tip Friml e...

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Section: Fypp1 and Fypp3 Directly Dephosphorylate Pin Proteinsmentioning

confidence: 52%

Section: Pp6 Acts Antagonistically With Pid To Regulate Plant Developmentioning

confidence: 99%

Section: Plant Materials and Growth Conditionsmentioning

confidence: 99%

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A PP6-Type Phosphatase Holoenzyme Directly Regulates PIN Phosphorylation and Auxin Efflux in Arabidopsis

et al. 2012

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“…Although it has been previously shown that PP2AA1 is localized cytosolically but cofractionates to an appreciable extent with plasma membrane proteins (Michniewicz et al, 2007;Blakeslee et al, 2008), to our knowledge, the effect of brefeldin on this localization has not yet been reported. PP2AA1-GFP permeated the cytoplasm; however, following 2-d treatment with as low as 3 mM brefeldin, appreciable PP2AA1-GFP moved into large central bodies (Figure 9) identified as nuclei by staining with a DNA-specific dye (see Supplemental Figure 5 online).…”

Section: Loss Of Pp2aa1 Enhances Responses To Brefeldinmentioning

confidence: 71%

Gravitropism ofArabidopsis thalianaRoots Requires the Polarization of PIN2 toward the Root Tip in Meristematic Cortical Cells

et al. 2010

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In the root, the transport of auxin from the tip to the elongation zone, referred to here as shootward, governs gravitropic bending. Shootward polar auxin transport, and hence gravitropism, depends on the polar deployment of the PIN-FORMED auxin efflux carrier PIN2. In Arabidopsis thaliana, PIN2 has the expected shootward localization in epidermis and lateral root cap; however, this carrier is localized toward the root tip (rootward) in cortical cells of the meristem, a deployment whose function is enigmatic. We use pharmacological and genetic tools to cause a shootward relocation of PIN2 in meristematic cortical cells without detectably altering PIN2 polarization in other cell types or PIN1 polarization. This relocation of cortical PIN2 was negatively regulated by the membrane trafficking factor GNOM and by the regulatory A1 subunit of type 2-A protein phosphatase (PP2AA1) but did not require the PINOID protein kinase. When GNOM was inhibited, PINOID abundance increased and PP2AA1 was partially immobilized, indicating both proteins are subject to GNOM-dependent regulation. Shootward PIN2 specifically in the cortex was accompanied by enhanced shootward polar auxin transport and by diminished gravitropism. These results demonstrate that auxin flow in the root cortex is important for optimal gravitropic response.

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“…In a recent study (Blakeslee et al, 2008), Arabidopsis rcn1-1 seedlings showed increased auxin transport but decreased root gravitropism. A sizeable fraction of RCN1 protein was localized in a microsomal membrane fraction in roots, and plants expressing YFP-RCN1 showed some enrichment adjacent to the plasma membrane as do both phot1 ) and phot2 (Kong et al, 2007).…”

Section: Discussionmentioning

confidence: 99%

The Arabidopsis rcn1-1 Mutation Impairs Dephosphorylation of Phot2, Resulting in Enhanced Blue Light Responses

Tseng

Briggs

2010

The Plant Cell

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Phototropins (phot) sense blue light through the two N-terminal chromophore binding LOV domains and activate the C-terminal kinase domain. The resulting phototropin autophosphorylation is essential for biological activity. We identified the A1 subunit of Ser/Thr protein phosphatase 2A (PP2A) as interacting with full-length phot2 in yeast and also interacting with phot2 in an in vitro protein binding assay. Phenotypic characterizations of a phot1-5 rcn1-1 (for root curling in n-naphthylphthalamic acid1) double mutant, in which phot2 is the only functional phototropin and PP2A activity is reduced, showed enhanced phototropic sensitivity and enhanced blue light-induced stomatal opening, suggesting that PP2A activity is involved in regulating phot2 function. When treated with cantharidin, a chemical inhibitor of PP2A, the phot1-5 mutant exhibited enhanced phot2-mediated phototropic responses like those of the phot1-5 rcn1-1 double mutant. Immunoblot analysis to examine phot2 endogenous phosphorylation levels and in vitro phosphorylation assays of phot2 extracted from plants during dark recovery from blue light exposure confirmed that phot2 is more slowly dephosphorylated in the reduced PP2A activity background than in the wild-type PP2A background, suggesting that phosphorylated phot2 is a substrate of PP2A activity. While reduced PP2A activity enhanced the activity of phot2, it did not enhance either phot1 dephosphorylation or the activity of phot1 in mediating phototropism or stomatal opening.

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Specificity of RCN1-Mediated Protein Phosphatase 2A Regulation in Meristem Organization and Stress Response in Roots

Cited by 75 publications

References 65 publications

A PP6-Type Phosphatase Holoenzyme Directly Regulates PIN Phosphorylation and Auxin Efflux in Arabidopsis

A PP6-Type Phosphatase Holoenzyme Directly Regulates PIN Phosphorylation and Auxin Efflux in Arabidopsis

Gravitropism ofArabidopsis thalianaRoots Requires the Polarization of PIN2 toward the Root Tip in Meristematic Cortical Cells

The Arabidopsis rcn1-1 Mutation Impairs Dephosphorylation of Phot2, Resulting in Enhanced Blue Light Responses

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