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Review

Plant PP2A: A Versatile Enzyme with Key Physiological Functions

by
Juan I. Cortelezzi
†,
Martina Zubillaga
†,
Victoria R. Scardino
,
María N. Muñiz García
* and
Daniela A. Capiati
*
Instituto de Investigaciones en Ingeniería Genética y Biología Molecular “Dr. Héctor Torres” (INGEBI), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Vuelta de Obligado 2490, Cuidad de Buenos Aires C1428ADN, Argentina
*
Authors to whom correspondence should be addressed.
†
These authors contributed equally to this work.
Kinases Phosphatases 2025, 3(1), 5; https://doi.org/10.3390/kinasesphosphatases3010005
Submission received: 31 January 2025 / Revised: 23 February 2025 / Accepted: 28 February 2025 / Published: 3 March 2025
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Abstract

:
Protein phosphatase 2A (PP2A) is a highly conserved heterotrimeric enzyme complex present in all eukaryotic cells, consisting of a scaffolding A subunit, a catalytic C subunit, and a regulatory B subunit. The A and C subunits form the core enzyme, which interacts with the B subunit to determine the substrate specificity, subcellular localization, and enzymatic activity of the holoenzyme. The Arabidopsis thaliana genome encodes five C subunits, three A subunits, and 17 B subunits, enabling the formation of diverse holoenzymes with extensive functional versatility. Genetic evidence highlights the essential role of PP2A in regulating various physiological processes in plants, including responses to abiotic and biotic stresses and developmental programs. Notably, PP2A can act as both a positive and negative regulator within the same pathway, while individual subunits often participate in multiple processes. This functional diversity arises from the structural flexibility of PP2A. This review examines the structural diversity of plant PP2A and its regulatory roles across diverse physiological contexts.

1. Introduction

Reversible protein phosphorylation is a key post-translational modification that regulates numerous cellular processes [1]. The phosphorylation state of a protein reflects the dynamic balance between the activities of protein kinases and protein phosphatases. Interestingly, in most organisms, the number of genes encoding protein kinases far exceeds those encoding protein phosphatases. In A. thaliana, 1125 protein kinases are counterbalanced by only 150 catalytic protein phosphatases [2]. Despite their lower numbers, protein phosphatases are thought to rival kinases in terms of substrate specificity, largely due to the extensive diversity of regulatory subunits that assemble into holoenzyme complexes [3].
Eukaryotic protein phosphatases are categorized into four major families: PPP (phosphoprotein phosphatase), PPM/PP2C (Mg2+- or Mn2+-dependent protein phosphatase/protein phosphatase 2C), PTP (phosphotyrosine phosphatase), and aspartate (Asp)-dependent phosphatases. The PPP and PPM families are serine/threonine-specific phosphatases, whereas the PTP and Asp-dependent enzymes include phosphatases with specificity for phospho-tyrosine, phospho-serine/-threonine, or both (dual-specificity phosphatases). Notably, PPPs are responsible for catalyzing over 80% of the protein dephosphorylation reactions in eukaryotic cells [1]. In plants, the PPP family is further divided into nine subfamilies: PP1 (protein phosphatase type one), PP2A (protein phosphatase 2A), PP4, PP5, PP6, PP7, SLP (Shewanella-like protein) phosphatase, and PPKL (protein phosphatase with Kelch-like repeat domains) [1]. Members of the PPP family exhibit high sequence and structural similarity and maintain an identical catalytic mechanism.
This review focuses on plant PP2A, aiming to provide a comprehensive update on the topic, with an emphasis on the versatile structure of plant PP2A and its multifaceted roles in regulating various physiological processes. We analyze the structure of PP2A, its subunits, and the regulation of its catalytic activity (Section 2), as well as the functions of PP2A in modulating responses to abiotic and biotic stresses and developmental programs (Section 3).

2. Structure of Plant PP2A: The Basis of Versatility

PP2A is a heterotrimeric enzyme complex present in all eukaryotic cells, composed of three subunits: a scaffolding A subunit, a regulatory B subunit, and a catalytic C subunit (Figure 1). The A and C subunits form the core enzyme, which interacts with the B subunit. This interaction determines the substrate specificity, cellular localization, and enzymatic activity of the A-B-C trimer. Additionally, PP2A can assemble into oligomeric complexes by associating with various regulatory molecules, including both activators and inhibitors [4].

2.1. PP2A Subunits

The C subunits of PP2A in various plant species are divided into two subfamilies: I and II. Subfamily I includes the Arabidopsis C1, C2, and C5 subunits, while subfamily II comprises the C3 and C4 subunits [6]. Both subfamilies share conserved domains and residues essential for binding regulatory B subunits. However, notable differences exist between the subfamilies in a domain potentially crucial for interactions with the scaffolding A subunits. Specifically, Glu284 in subfamily I and Asp284 in subfamily II are located within conserved regions that influence binding specificity to A subunits in Arabidopsis [7,8]. This region may play a critical role in determining the formation of distinct PP2A holoenzymes with specialized functional activities. The active site of PP2A C subunits contains highly conserved residues that chelate two metal ions essential for catalytic function [9]. The catalytic domain also has a unique C-terminal tail with a conserved motif (TPDYFL). The methylation of the carboxyl group at the terminal Leu is crucial for recruiting and binding B subunits to the A–C dimer, facilitating the assembly of functional PP2A holoenzymes [10].
The A subunit consists of 15 tandem repeats of the α-helical HEAT (huntingtin-elongation-A subunit-TOR) motif, each comprising 39 amino acids that together form a horseshoe-shaped scaffold [11]. Conserved loops within the HEAT repeats play a critical role in binding both the C and B subunits [12]. In Arabidopsis, three distinct isoforms of the A subunit have been identified: ROOTS CURL IN NAPHTHYLPHTHALAMIC ACID1 (RCN1)/PP2A-A1, PP2A-A2, and PP2A-A3 [6].
In plants, the B subunits of PP2A are encoded by three unrelated and structurally distinct gene families: B/B55, B′/B56, and B″/B72. The Arabidopsis genome encodes two, nine, and six genes for B, B′, and B″ subunits, respectively [6]. All B subunit families share two conserved A subunit-binding domains, ASBD1 and ASBD2, within their core region, which are essential for interaction with the A–C dimer [13]. Despite these conserved regions, the families exhibit unique structural features [4]. B family isoforms contain multiple WD40 repeats, while B′ members possess a B56 domain with eight HEAT repeats and show variability in their N- and C-terminal regions. B″ subunits are characterized by the presence of EF-hand motif domains.

2.2. Number and Subcellular Localization of PP2A Subunits

Plants possess a greater number of PP2A genes than animals, reflecting their functional expansion and diversification. The Arabidopsis genome encodes five C subunits, three A subunits, and 17 regulatory B subunits [6], whereas the Drosophila genome contains only one gene each for the C and A subunits, along with five genes for regulatory B subunits [14]. This expanded gene repertoire in plants also suggests a higher degree of genetic redundancy, supporting their complex regulatory needs.
Plant PP2A subunits exhibit variations in isoform numbers and subcellular localization. Analysis of data from three species belonging to different genera (A. thaliana, S. tuberosum, and Hevea brasiliensis) reveals that the number of C subunits ranges from five to eight, A subunits from three to five, and regulatory B subunits from 17 to 24 (Table 1). This diversity enables the formation of numerous distinct holoenzymes, contributing to extensive functional versatility. For instance, Arabidopsis can theoretically form 255 heterotrimeric PP2A combinations. However, the actual availability of these subunits for holoenzyme assembly is determined by their spatiotemporal gene expression patterns [15].
Analysis of the predicted subcellular localization of PP2A subunits using in silico methods shows that C subunits have a relatively restricted range of subcellular locations, being predominantly cytosolic (Table 1). In contrast, A and B subunits exhibit a wide variety of predicted localizations. In Arabidopsis, experimental data also support the diverse localization of regulatory B subunits [15,16]. This variability in A and B subunits underlies the multiple localization patterns and substrate specificities of the holoenzyme.
Table 1. Main subcellular localization of PP2A subunits of Arabidopsis thaliana, S. tuberosum (potato), and Hevea brasiliensis (rubber tree), predicted by WoLF PSORT (https://wolfpsort.hgc.jp/; accessed on 15 January 2025) and SUBA (https://suba.live/, accessed on 15 January 2025). Sequences of the subunits were retrieved from Zubillaga et al. [5] and Chao et al. [17]. T2/F1: TON2/FASS1; Cyt: cytosol; PM: plasma membrane; nu: nucleus; chl: chloroplast; ER: endoplasmic reticulum; cysk: cytoskeleton; mito: mitochondria.
Table 1. Main subcellular localization of PP2A subunits of Arabidopsis thaliana, S. tuberosum (potato), and Hevea brasiliensis (rubber tree), predicted by WoLF PSORT (https://wolfpsort.hgc.jp/; accessed on 15 January 2025) and SUBA (https://suba.live/, accessed on 15 January 2025). Sequences of the subunits were retrieved from Zubillaga et al. [5] and Chao et al. [17]. T2/F1: TON2/FASS1; Cyt: cytosol; PM: plasma membrane; nu: nucleus; chl: chloroplast; ER: endoplasmic reticulum; cysk: cytoskeleton; mito: mitochondria.
ArabidopsisPotatoRubber Tree
WoLF PSORTSUBA WoLF PSORT WoLF PSORT
CC1cytPMC1cytC1-1cyt
C2cytPMC2acytC1-2cyt
C3cytcytC2bcytC2-1cyt
C4cytcytC3cytC2-2cyt
C5cytcytC4cytC4-1cyt/nu
C5cytC4-2nu
C4-3cyt
C6cyt
AA1cyt/chlPMA1PMA1-1cyt
A2chlgolgiA2cytA1-2ER
A3chlcytA3cytA2chl
A3cyt
BBαnunuBαnuBα-1nu
BβcysknuBβnuBα-2cyt
BγcytBα-3ER
BδnuBβcysk
B′B′αmitonuB′αmitoB′αcyt
B′βmitonuB′βmitoB′βcyt
B′γmitoplastidB′γmitoB′γmito
B′δcytgolgiB′δmitoB′ζnu
B′εcytnuB′εmitoB′η-1mito
B′ζmitomitoB′ζcytB′η-2mito
B′ηcytnu/cytB′ηmitoB′η-3mito
B′θmitomitoB′θcytB′η-4mito
B′κmitoplastidB′ιmitoB′η-5chl
B′κnuB′θ-1mito
B′λmitoB′θ-2mito
B′κ-1mito
B′κ-2chl
B′μnu/mito
B″B″αnucytB″αnuB″αnu
B″βnunuB″βcytB″βnu
B″γnucytB″γnu/cytB″δcyt
B″δnucyt B″εnu/cyt/chl
B″εnucyt T2/F1-1nu
T2/F1nucyt T2/F1-2nu/cyt

2.3. Regulation of PP2A Activity

In addition to the functional versatility provided by the number of possible holoenzyme combinations, PP2A activity is further modulated by post-translational modifications and regulatory proteins.
Holoenzyme assembly is partially regulated by the methylation of the catalytic subunits at the carboxyl group of the terminal Leu in the TPDYFL motif [10]. This methylation neutralizes the negative charge of the carboxyl terminus, thereby facilitating the interaction between regulatory B subunits and A-C dimers [12]. In Arabidopsis, this reversible modification is catalyzed by the SUPPRESSOR OF BRI1 (SBI1), a homolog of the mammalian Leucine Carboxyl Methyltransferase 1 (LCMT1) [18]. Additionally, the Arabidopsis PHOSPHOTYROSYL PHOSPHATASE ACTIVATOR (AtPTPA) plays a role in promoting PP2A methylation and holoenzyme assembly [19].
Most PP2A holoenzymes consist of a stable A-C heterodimer, which associates with different regulatory B subunits. However, a small fraction of the C subunits that are not bound to the A subunit interact with a structurally distinct protein known as TAP46 (PP2A Phosphatase-Associated Protein of 46 kDa). TAP46 is the Arabidopsis homolog of the mammalian α4 and yeast Tap42 proteins [20]. The effect of this interaction on catalytic activity remained unknown until recently, when it was demonstrated that wheat TaTAP46 interacts with the C subunits and inhibits their enzymatic activities [21].

3. Physiological Roles of Plant PP2A

3.1. Abiotic Stress

Accumulating evidence reveals that PP2A plays a crucial role in regulating plant responses to drought and osmotic and salt stresses. Genetic manipulation of the C subunits impacts abiotic stress response in different plant species. Overexpression of the PP2A-C5 gene confers increased salt tolerance in A. thaliana [22]. Overexpression of the wheat C subunit TaPP2Ac-1 enhances drought tolerance in transgenic tobacco plants [23]. Interestingly, recent findings reveal that silencing another wheat C subunit, TaPP2A-2, also improves drought tolerance [21].
The role of PP2A C subunits in abiotic stress responses has been extensively studied in potato [24]. Phenotypic analysis of potato plants overexpressing StPP2A-C2b demonstrated that this catalytic subunit functions as a positive regulator of the molecular acclimation response to abiotic stress [5]. However, transgenic plants showed reduced tuber yields under drought conditions [25]. This reduction in yield could be attributed to the fact that crop performance under adverse environmental conditions is influenced by numerous factors and reflects a complex interplay of molecular, biochemical, and physiological responses. Overexpression of StPP2A-C2b impacts various physiological processes, such as stomatal function and senescence, which might contribute to reduced yields under drought conditions despite the enhanced molecular stress response observed in the transgenic plants. Consequently, it is crucial to consider the broad range of physiological processes regulated by PP2A when evaluating the functional roles of this enzyme through the genetic manipulation of its subunits.
The response to abiotic stress can be altered not only by genetically manipulating the catalytic subunits but also by modifying the A and B subunits. In Arabidopsis, mutation of the RCN1/A1 gene, which encodes an A subunit isoform, increases sensitivity to both salt and osmotic stress [26]. Additionally, transgenic Arabidopsis plants overexpressing the wheat B″ subunit TaPP2AbB″-α exhibit enhanced root growth under osmotic and salt-stress conditions [27]. Similarly, overexpression of TaPP2AbB″-γ improves osmotic and salt-stress tolerance in transgenic Arabidopsis seedlings [28]. More recently, functional analyses revealed that overexpressing the B″ subunit gene GmPP2A-B″71 in soybean enhances tolerance to both drought and salt stress, while silencing this gene increases sensitivity to these stresses [29]. These findings underscore the key role of regulatory B subunits in modulating holoenzyme activity.
The available genetic evidence, summarized in Table 2, highlights the critical role of PP2A in abiotic stress responses, suggesting that PP2A can function as either a positive or negative regulator of these processes at both molecular and physiological levels. Despite the significance of PP2A in abiotic stress responses, the molecular mechanisms underlying its function remain largely unknown due to the limited information on the substrates of PP2A involved in these processes. Hu et al. [22] identified four vacuolar membrane chloride channels (CLCs) that interact with the catalytic subunit PP2A-C5 in Arabidopsis, and these channels are known to contribute positively to salt-stress tolerance. This suggests that PP2A-C5 may enhance salinity tolerance by modulating CLC activity. Liu et al. [28] demonstrated that the wheat TaPP2AbB″-γ subunit interacts with TaBZR1, a positive regulator of brassinosteroid signaling, which is upregulated in roots during salt stress. This interaction suggests that TaPP2AbB″-γ plays a role in improving abiotic stress tolerance by directly binding to TaBZR1. These reports have provided valuable insights into the mechanisms by which PP2A functions during abiotic stress responses. However, it remains to be confirmed whether CLCs and TaBZR1 are direct substrates of PP2A.

3.2. Biotic Stress

A growing number of studies demonstrate that PP2A plays a pivotal role in plant resistance and immunity, particularly in responses to fungal pathogens. These findings are based on research involving the silencing, knockout, or overexpression of PP2A catalytic, scaffolding, or regulatory subunits across various plant species. For instance, silencing the subfamily I of PP2A catalytic subunits in N. benthamiana enhances the hypersensitive response to effector proteins from Cladosporium fulvum and the bacterium Pseudomonas syringae [30]. Similarly, Zhu et al. [31] reported that the silencing of a wheat PP2A catalytic subunit (TaPP2Ac-4D) increases resistance to Rhizoctonia cerealis. In contrast, Lin et al. [32] showed that in rice, the knockout of OsPP2A-1, encoding a catalytic subunit, increases susceptibility to Rhizoctonia solani, whereas its overexpression confers resistance. Moreover, the overexpression of StPP2A-C2b in potato has been found to increase susceptibility to the oomycete Phytophthora infestans [33].
For A subunits, Chen et al. [34] demonstrated that silencing PP2Aa in Nicotiana benthamiana reduces resistance to the oomycete Phytophthora capsici. Regarding B subunits, PP2A-B′γ has been implicated in the regulation of defense in Arabidopsis. Phenotypic analysis of the pp2a-b′γ mutant revealed enhanced resistance to Botrytis cinerea [35,38].
As for abiotic stress, PP2A plays a fundamental role in the response to pathogens, either enhancing or reducing resistance to infection (Table 2). Regarding the molecular mechanisms underlying PP2A-mediated defense responses, Segonzac et al. [42] demonstrated that PP2A functions as a negative regulator of plant innate immunity. Specifically, PP2A modulates the activity of surface-localized pattern-recognition receptors (PRRs), which are key activators of immune responses, by regulating the phosphorylation status of the PRR co-receptor BAK1. The PP2A holoenzyme involved in this process is likely composed of the subunits A1, C4, and B′η/ζ. Recent findings indicate that PP2A also mediates the dephosphorylation of the Arabidopsis transcription factor bZIP59 [43]. bZIP59 plays a central role in regulating the shade avoidance response and stomatal immunity, a defense mechanism that enables plants to rapidly close their stomata to prevent pathogen entry [44]. Multiple reports suggest that PP2A contributes to plant immunity by inducing the expression of pathogenesis-related genes [31,32,33]; however, the signaling components responsible for this regulation remain unclear. Emerging evidence also highlights PP2A as a critical player in oxidative stress signaling, which influences cell death and defense responses against biotic stressors [45]. Studies using PP2A inhibitors and mutants indicate that PP2A negatively regulates oxidative stress responses by limiting excessive reactive oxygen species (ROS) accumulation. For example, wheat plants with a silenced PP2A catalytic subunit (TaPP2Ac) exhibit increased expression of antioxidant enzyme genes, such as CAT and APX2 [31]. Collectively, these findings suggest that PP2A integrates multiple signaling pathways that contribute to diverse biotic stress responses, underscoring the multifunctional nature of this enzyme.

3.3. Developmental Programs

PP2A is involved in various processes related to plant development, including the regulation of tuber formation in potato. PP2A plays a pivotal role in controlling tuber development [46]. The catalytic subunit StPP2A-C2b functions in stolons as a positive regulator of tuber induction by integrating multiple tuberization-related signals, primarily through the modulation of gibberellic acid metabolism, a key negative regulator of tuberization [36]. Once the tuber is formed, StPP2A-C2b regulates tuber sprouting. Tubers overexpressing this catalytic subunit exhibit delayed sprouting, altered apical dominance, and branched sprouts, along with changes in the source-sink balance between the tuber and the sprouts [37].
Recent studies have shown that PP2A is involved in the regulation of plant senescence. In Arabidopsis, analysis of the pp2a-b′γ mutant revealed that PP2A-B′γ acts as a negative regulator of developmental senescence [38]. Conversely, in potato, the catalytic subunit StPP2A-C2b functions as a positive regulator of developmental senescence, pathogen-induced senescence, and localized cell death triggered by mechanical damage [33].
PP2A is a key regulator of stomatal development. In Arabidopsis, PP2A modulates the activity of the transcription factor SPCH, a regulator of stomatal formation. PP2A promotes SPCH stability through dephosphorylation [39]. Loss-of-function mutants of A subunit genes (pp2a-a1, pp2a-a1;a2, and pp2a-a1;a3) exhibit reduced stomatal production. In potato plants, StPP2A-C2b is involved in stomatal formation, potentially by modulating the expression of StFAMA, another regulator of stomatal formation [25]. Leaves of plants overexpressing StPP2A-C2b show decreased stomatal density and increased stomatal size.
An intriguing recently described function of PP2A is the regulation of plant growth in response to plant-growth-promoting rhizobacteria (PGPR). Studies on tomato plants overexpressing PP2A B′θ revealed that this regulatory subunit negatively regulates growth, development, and mycorrhization following treatment with Azospirillum brasilense and Pseudomonas simiae [40]. Moreover, analysis of the Arabidopsis double mutant c2c5 demonstrated that the catalytic subunits PP2A-C2 and PP2A-C5 promote growth in response to these PGPR [41].
The roles of PP2A in plant development are likely linked to its involvement in regulating cell division as the formation of new cell types and tissues relies on coordinated and spatially oriented cell divisions. The first evidence for PP2A’s role in this process was provided by Spinner et al. [47], who reported that PP2A holoenzyme with TON2/FASS1 as regulatory subunit spatially regulates cell division. Subsequently, the C subunit PP2A-3 was identified as a key regulator of formative cell divisions in Arabidopsis, acting through the reciprocal regulation of ACR4, a molecular component of the mechanism controlling cell divisions in the root [48]. Additionally, Yuan et al. [49] demonstrated that the combined loss of the regulatory subunits PP2AB′α and PP2AB′β in Arabidopsis results in premature chromosome cohesion loss during meiosis. This finding suggests that PP2AB′α and PP2AB′β are critical components of the molecular machinery that governs reductional cell division in meiosis. Collectively, these studies underscore the pivotal role of PP2A in regulating both mitotic and meiotic processes.

4. Conclusions and Future Perspectives

The available genetic evidence, summarized in Table 2, underscores the critical role of PP2A in numerous physiological processes. Interestingly, PP2A can function as either a positive or negative regulator of the same process, and a single subunit can regulate multiple processes. This functional diversity is rooted in the structural versatility of PP2A, which arises from its ability to form distinct holoenzymes (Figure 2). Each B regulatory subunit can associate with multiple combinations of A–C dimers, generating a variety of trimeric holoenzymes with different subcellular localizations and substrate specificities. In addition, PP2A activity can be further modulated by regulatory proteins such as TAP46 or AtPTPA. This versatility enables PP2A to modulate a wide range of cellular responses in both redundant and opposing ways.
While there is substantial information about the roles of different PP2A subunits in various physiological processes, little is known about the underlying molecular mechanisms, with a few exceptions (Figure 2). To address this, it is essential to identify the substrates dephosphorylated by PP2A during these processes and determine the composition of the PP2A molecular complex operating under different physiological conditions.
Given that PP2A regulates key physiological processes essential for plant survival, its study is of clear importance. A comprehensive understanding of PP2A’s mechanisms of action will enable the development of strategies to enhance crop resilience to climate change and resistance to pathogens. Although the direct manipulation of PP2A subunits is a viable approach, it may lead to adverse effects on growth and development, ultimately compromising the yield due to the broad range of processes regulated by this enzyme. Targeting PP2A substrates or modulating its interactions with other proteins presents a more precise and specific alternative. In potato, the catalytic subunit StPP2Ac2b has been shown to positively regulate molecular responses to salt and osmotic stress [5]; however, its overexpression results in reduced yields due to its impact on multiple physiological processes [25]. Identifying the substrates of StPP2Ac2b under stress conditions will be key to designing effective strategies for the development of drought- and salt-tolerant potato cultivars. A compelling example of how elucidating PP2A’s fundamental mechanisms can contribute to crop improvement is the study by Chen et al. [34]. This research demonstrated that the effector PcAvh1 from the oomycete Phytophthora capsici interacts with the scaffolding A subunit of PP2A. Disrupting this interaction could potentially reduce pathogen virulence, offering a promising strategy for developing crops resistant to Phytophthora species.

Supplementary Materials

The following supporting information can be downloaded at https://www.mdpi.com/article/10.3390/kinasesphosphatases3010005/s1. Figure S1: Residue–residue alignment confidence (PAE) plots corresponding of the models depicted in Figure 1.

Author Contributions

All authors contributed to study conception, design, and writing. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Data Availability Statement

The original contributions presented in this study are included in the article/Supplementary Material. Further inquiries can be directed to the corresponding authors.

Conflicts of Interest

The authors declare no conflicts of interest.

Abbreviations

The following abbreviations are used in this manuscript:
PP2AProtein phosphatase 2A
PPPPhosphoprotein phosphatase
PPMMg2+- or Mn2+-dependent protein phosphatase
PP2CProtein phosphatase 2C
PTPPhosphotyrosine phosphatase
PP1Protein phosphatase 1
PP4Protein phosphatase 4
PP5Protein phosphatase 5
PP6Protein phosphatase 6
PP7Protein phosphatase 7
SLPShewanella-like protein phosphatase
PPKLProtein phosphatase with Kelch-like repeat domains
T2/F1TON2/FASS1
CytCytosol
PMPlasma membrane
NuNucleus
ChlChloroplast
EREndoplasmic reticulum
Cysk Cytoskeleton
Mito Mitochondria
SBI1SUPPRESSOR OF BRI1
LCMT1Leucine Carboxyl Methyltransferase 1
PTPAPHOSPHOTYROSYL PHOSPHATASE ACTIVATOR
PGPRPlant-growth-promoting rhizobacteria

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Figure 1. Predicted structure of Solanum tuberosum PP2A subunits generated using the AlphaFold Protein Structure Database (https://alphafold.ebi.ac.uk/, accessed on 15 January 2025). The protein sequences used for modeling were as follows: StPP2A-C1 (Soltu.DM.05G006870.1-magenta), StPP2A-A3 (Soltu.DM.06G025160.1-yellow), StPP2A-Bα (Soltu.DM.03G036140.3-blue), StPP2A-B′α (Soltu.DM.09G005170.1-blue), and StPP2A-B″β (Soltu.DM.05G025530.1-blue). These sequences were retrieved from the Spud DB Potato Genomic Resource (https://spuddb.uga.edu/, accessed on 15 January 2025), as described by Zubillaga et al. [5]. The residue–residue alignment confidence (PAE) plots are show in Supplementary Figure S1.
Figure 1. Predicted structure of Solanum tuberosum PP2A subunits generated using the AlphaFold Protein Structure Database (https://alphafold.ebi.ac.uk/, accessed on 15 January 2025). The protein sequences used for modeling were as follows: StPP2A-C1 (Soltu.DM.05G006870.1-magenta), StPP2A-A3 (Soltu.DM.06G025160.1-yellow), StPP2A-Bα (Soltu.DM.03G036140.3-blue), StPP2A-B′α (Soltu.DM.09G005170.1-blue), and StPP2A-B″β (Soltu.DM.05G025530.1-blue). These sequences were retrieved from the Spud DB Potato Genomic Resource (https://spuddb.uga.edu/, accessed on 15 January 2025), as described by Zubillaga et al. [5]. The residue–residue alignment confidence (PAE) plots are show in Supplementary Figure S1.
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Figure 2. Schematic representation of the structural and functional versatility of plant PP2A. Regulatory proteins are depicted as magenta ovals, while PP2A substrates or potential substrates are shown as green squares.
Figure 2. Schematic representation of the structural and functional versatility of plant PP2A. Regulatory proteins are depicted as magenta ovals, while PP2A substrates or potential substrates are shown as green squares.
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Table 2. Diversity of physiological functions of PP2A, evidenced by manipulation of the subunit genes.
Table 2. Diversity of physiological functions of PP2A, evidenced by manipulation of the subunit genes.
SpeciesSubunitEffectReference
Abiotic stressA. thalianaPP2AC-5 (C) overexpressionIncreased salt-stress tolerance[22]
Triticum aestivumTaPP2Ac-1 (C) overexpressionIncreased drought tolerance[23]
T. aestivumTaPP2A-2 (C) silencingIncreased drought tolerance[21]
S. tuberosumStPP2A-C2b (C) overexpressionEnhanced molecular response to abiotic stress[5]
A. thalianaRCN1/A1 (A) mutationIncreased sensitivity to drought and salt stress[26]
T. aestivumTaPP2AbB″-α (B) overexpressionIncreased drought and osmotic stress tolerance[27]
T. aestivumTaPP2AbB″-γ (B) overexpressionIncreased drought and osmotic stress tolerance[28]
Glycine maxGmPP2A-B″71 (B) overexpressionIncreased drought and salt-stress tolerance[29]
Biotic stressNicotiana benthamianaC subfamily I silencingEnhanced hypersensitive response [30]
T. aestivumTaPP2Ac-4D (C) silencingIncreased pathogen resistance [31]
Oryza sativaOsPP2A-1 (C) knockoutIncreased pathogen susceptibility [32]
S. tuberosumStPP2A-C2b (C) overexpressionIncreased pathogen susceptibility [33]
N. benthamianaPP2Aa (A) silencingIncreased pathogen susceptibility[34]
A. thalianaPP2A-B′γ (B) mutationIncreased pathogen resistance [35]
DevelopmentS. tuberosumStPP2A-C2b (C) overexpressionEnhanced tuber development[36]
S. tuberosumStPP2A-C2b (C) overexpressionDelayed tuber sprouting[37]
A. thalianaPP2A-B′γ (B) mutationDelayed senescence [38]
S. tuberosumStPP2A-C2b (C) overexpressionAccelerated senescence[33]
A. thalianaPP2A-A1 (A) PP2A-A1/A2 (A) PP2A-A1/A3 (A) mutationReduced stomatal production[39]
S. tuberosumStPP2A-C2b (C) overexpressionReduced stomatal density and increased stomatal size[25]
Solanum lycoperiscumPP2A B′θ (B) overexpressionDecreased growth in response to PGPR[40]
A. thalianaPP2A-C2/C5 (C) mutationEnhanced growth in response to PGPR[41]
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Cortelezzi, J.I.; Zubillaga, M.; Scardino, V.R.; Muñiz García, M.N.; Capiati, D.A. Plant PP2A: A Versatile Enzyme with Key Physiological Functions. Kinases Phosphatases 2025, 3, 5. https://doi.org/10.3390/kinasesphosphatases3010005

AMA Style

Cortelezzi JI, Zubillaga M, Scardino VR, Muñiz García MN, Capiati DA. Plant PP2A: A Versatile Enzyme with Key Physiological Functions. Kinases and Phosphatases. 2025; 3(1):5. https://doi.org/10.3390/kinasesphosphatases3010005

Chicago/Turabian Style

Cortelezzi, Juan I., Martina Zubillaga, Victoria R. Scardino, María N. Muñiz García, and Daniela A. Capiati. 2025. "Plant PP2A: A Versatile Enzyme with Key Physiological Functions" Kinases and Phosphatases 3, no. 1: 5. https://doi.org/10.3390/kinasesphosphatases3010005

APA Style

Cortelezzi, J. I., Zubillaga, M., Scardino, V. R., Muñiz García, M. N., & Capiati, D. A. (2025). Plant PP2A: A Versatile Enzyme with Key Physiological Functions. Kinases and Phosphatases, 3(1), 5. https://doi.org/10.3390/kinasesphosphatases3010005

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