Disparate Roles for the Regulatory A Subunit Isoforms in Arabidopsis Protein Phosphatase 2A

Zhou, Hongwei; Nussbaumer, Cindy; Chao, Yvonne; DeLong, Alison

doi:10.1105/tpc.018994

Cited by 97 publications

(133 citation statements)

References 61 publications

(79 reference statements)

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“…pp2aa mutants were the kind gift of A. Delong 25 . The ton1 mutant carries a deletion affecting both TON1a and TON1b genes 11 .…”

Section: Methodsmentioning

confidence: 99%

“…PP2AA1 is considered to have a cardinal role in seedlings. Although morphologically similar to the wild type, PP2AA1 mutants display abnormal ethylene and ABA responses, as well as perturbed polar auxin transport [22][23][24][25] . PP2AA2 and PP2AA3 functions are unmasked only in a pp2aa1 mutant background 25 and neither pp2aa2 and pp2aa3 mutant nor pp2aa2-a3 double mutant plants have altered morphological phenotypes per se (see ref.…”

Section: Ton1mentioning

confidence: 99%

“…PP2AA2 and PP2AA3 functions are unmasked only in a pp2aa1 mutant background 25 and neither pp2aa2 and pp2aa3 mutant nor pp2aa2-a3 double mutant plants have altered morphological phenotypes per se (see ref. 25 and Fig. 2a).…”

Section: Ton1mentioning

confidence: 99%

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A protein phosphatase 2A complex spatially controls plant cell division

et al. 2013

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In the absence of cell migration, the orientation of cell divisions is crucial for body plan determination in plants. The position of the division plane in plant cells is set up premitotically via a transient cytoskeletal array, the preprophase band, which precisely delineates the cortical plane of division. Here we describe a protein complex that targets protein phosphatase 2A activity to microtubules, regulating the transition from the interphase to the premitotic microtubule array. This complex, which comprises TONNEAU1 and a PP2A heterotrimeric holoenzyme with FASS as regulatory subunit, is recruited to the cytoskeleton via the TONNEAU1-recruiting motif family of proteins. Despite the acentrosomal nature of plant cells, all members of this complex share similarity with animal centrosomal proteins involved in ciliary and centriolar/centrosomal functions, revealing an evolutionary link between the cortical cytoskeleton of plant cells and microtubule organizers in other eukaryotes.

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“…pp2aa mutants were the kind gift of A. Delong 25 . The ton1 mutant carries a deletion affecting both TON1a and TON1b genes 11 .…”

Section: Methodsmentioning

confidence: 99%

Section: Ton1mentioning

confidence: 99%

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A protein phosphatase 2A complex spatially controls plant cell division

et al. 2013

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“…B subunits bind to repeats 1 to 10, whereas C subunits bind to repeats 11 to 15 (Li and Virshup, 2002). The Arabidopsis A subunits have been studied by different research groups, and are known to be important for root morphology (Zhou et al, 2004) and auxin transport (Michniewicz et al, 2007). They show overlapping functions, and the triple knockout is most likely lethal (Zhou et al, 2004;Michniewicz et al, 2007).…”

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confidence: 99%

Protein Phosphatase 2A B55 and A Regulatory Subunits Interact with Nitrate Reductase and Are Essential for Nitrate Reductase Activation

et al. 2011

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Posttranslational activation of nitrate reductase (NR) in Arabidopsis (Arabidopsis thaliana) and other higher plants is mediated by dephosphorylation at a specific Ser residue in the hinge between the molybdenum cofactor and heme-binding domains. The activation of NR in green leaves takes place after dark/light shifts, and is dependent on photosynthesis. Previous studies using various inhibitors pointed to protein phosphatases sensitive to okadaic acid, including protein phosphatase 2A (PP2A), as candidates for activation of NR. PP2As are heterotrimeric enzymes consisting of a catalytic (C), structural (A), and regulatory (B) subunit. In Arabidopsis there are five, three, and 18 of these subunits, respectively. By using inducible artificial microRNA to simultaneously knock down the three structural subunits we show that PP2A is necessary for NR activation. The structural subunits revealed overlapping functions in the activation process of NR. Bimolecular fluorescence complementation was used to identify PP2A regulatory subunits interacting with NR, and the two B55 subunits were positive. Interactions of NR and B55 were further confirmed by the yeast two-hybrid assay. In Arabidopsis the B55 group consists of the close homologs B55a and B55b. Interestingly, the homozygous double mutant (b55a 3 b55b) appeared to be lethal, which shows that the B55 group has essential functions that cannot be replaced by other regulatory subunits. Mutants homozygous for mutation in Bb and heterozygous for mutation in Ba revealed a slower activation rate for NR than wild-type plants, pointing to these subunits as part of a PP2A complex responsible for NR dephosphorylation.Nitrate reductase (NR), a key enzyme in nitrogen assimilation, reduces nitrate to nitrite in the cytosol. The nitrite formed is further reduced to ammonium in the plastids, whereafter ammonium is incorporated into amino acids. Regulation of NR takes place at the transcriptional as well as posttranslational level. At both levels signals from the chloroplasts are involved in initiating an increase in NR activity levels, but these signals and their processing are still unknown (Jonassen et al.,

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“…Phosphorylation has been shown to be important for auxin transport and distribution (17)(18)(19)(20). So far, the only known regulators that specifically regulate the PIN polar targeting are the serine/threonine protein kinase PINOID (PID) (18)(19)(20) and the protein phosphatase 2A (PP2A) (21,22) that mediate antagonistically the phosphorylation of PIN proteins (22). Loss-of-function pid mutant leads to a preferentially basal (lower cell side) PIN localization (23), whereas pid gain-of-function and pp2a loss-of-function mutants favor an apical (upper cell side) PIN localization (22,23).…”

mentioning

confidence: 99%

PIN phosphorylation is sufficient to mediate PIN polarity and direct auxin transport

Zhang

Nodzyński

Pěnčík

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

176

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The plant hormone auxin plays a crucial role in regulating plant development and plant architecture. The directional auxin distribution within tissues depends on PIN transporters that are polarly localized on the plasma membrane. The PIN polarity and the resulting auxin flow directionality are mediated by the antagonistic actions of PINOID kinase and protein phosphatase 2A. However, the contribution of the PIN phosphorylation to the polar PIN sorting is still unclear. Here, we identified an evolutionarily conserved phosphorylation site within the central hydrophilic loop of PIN proteins that is important for the apical and basal polar PIN localizations. Inactivation of the phosphorylation site in PIN1(Ala) resulted in a predominantly basal targeting and increased the auxin flow to the root tip. In contrast, the outcome of the phosphomimic PIN1(Asp) manipulation was a constitutive, PINOID-independent apical targeting of PIN1 and an increased auxin flow in the opposite direction. Furthermore, the PIN1(Asp) functionally replaced PIN2 in its endogenous expression domain, revealing that the phosphorylation-dependent polarity regulation contributes to functional diversification within the PIN family. Our data suggest that PINOID-independent PIN phosphorylation at one single site is adequate to change the PIN polarity and, consequently, to redirect auxin fluxes between cells and provide the conceptual possibility and means to manipulate auxin-dependent plant development and architecture.cell polarity | auxin distribution | plant architecture T he plant hormone auxin acts, on account of its differential distribution (gradients) within tissues, as a major determinant of plant architecture (1-3). Auxin is distributed throughout the plant by a network of carrier proteins (4-8), and the directionality of the auxin flow is determined by asymmetrically localized plasma membrane PIN transporters (9). The differentially expressed and polarly localized PIN proteins constitute the backbone of a transport network for directional auxin distribution in different parts of the plant (10). The local biosynthesis (11-13) together with the PIN-dependent transport (14) largely account for the formation of local auxin maxima and minima that regulate various developmental processes, including embryonic axis establishment, tropic growth, root meristem patterning, lateral organ and fruit formation, and vascular tissue differentiation and regeneration (15, 16). The polar PIN localization determines direction of the auxin flow; thus, any signal that acts upstream to control the cellular PIN localization and activity can be translated into changes in the auxin distribution that modulate multiple aspects of the plant development. Phosphorylation has been shown to be important for auxin transport and distribution (17)(18)(19)(20). So far, the only known regulators that specifically regulate the PIN polar targeting are the serine/threonine protein kinase PINOID (PID) (18-20) and the protein phosphatase 2A (PP2A) (21, 22) that mediate antagonistical...

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Disparate Roles for the Regulatory A Subunit Isoforms in Arabidopsis Protein Phosphatase 2A

Cited by 97 publications

References 61 publications

A protein phosphatase 2A complex spatially controls plant cell division

A protein phosphatase 2A complex spatially controls plant cell division

Protein Phosphatase 2A B55 and A Regulatory Subunits Interact with Nitrate Reductase and Are Essential for Nitrate Reductase Activation

PIN phosphorylation is sufficient to mediate PIN polarity and direct auxin transport

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