bims-plator Biomed News
on Plant TOR
Issue of 2026–05–10
eight papers selected by
Christian Meyer, INRAE
  1. pH-mediated activation of the lysosomal arginine sensor SLC38A9.
  2. Dynamic and Basal Phosphorylation Landscapes of Abscisic Acid Signaling Revealed by Phosphoproteome Analysis in Arabidopsis.
  3. PHR1 mediates rapid high light responses and acclimation to high photosynthetic activity.
  4. Arabidopsis inositol polyphosphate kinase activities regulate COP9 deneddylation functions in phosphate homeostasis.
  5. Abscisic acid binds to an Arabidopsis thaliana phosphodiesterase and tunes its activity.
  6. Plasmodesmal closure elicits stress responses.
  7. Cell-type-specific autophagy in root-hair-forming cells is essential for salt stress tolerance in Arabidopsis thaliana.
  8. StWRKY46 promotes stomatal closure and enhances potato drought tolerance by mediating the PYL1-ABI2-OST1/SnRK2.5/SnRK2.6 pathway.
  1. FEBS Lett. 2026 May 03.
    pH-mediated activation of the lysosomal arginine sensor SLC38A9.
    Xuelang Mu, Ampon Sae Her, Tamir Gonen.
      Cells rely on metabolic control; the mechanistic target of rapamycin complex 1 (mTORC1) senses nutrient availability, particularly amino acids. Lysosomes maintain amino acid homeostasis through recycling. SLC38A9, a lysosomal amino acid transporter, functions as a critical sensor in the mTORC1 pathway. Here, we investigate how pH regulates SLC38A9 activity. We show that arginine uptake is pH-dependent, with His544 residue serving as the pH sensor. Mutating His544 abolishes pH dependence without impairing overall transport, indicating His544 influences transport through protonation/deprotonation, instead of involving in the substrate binding. We propose a working model for pH-induced activation, through comparing two determined SLC38A9 structures at different pH. These findings reveal how local ionic shifts regulate lysosomal transporters and fine-tune SLC38A9 function to control mTORC1 signaling.
    Keywords:  SLC family; amino acid transport; mTOR complex; pH‐regulation; transceptor
    DOI:  https://doi.org/10.1002/1873-3468.70352
  2. Int J Mol Sci. 2026 Apr 15. pii: 3532. [Epub ahead of print]27(8):
    Dynamic and Basal Phosphorylation Landscapes of Abscisic Acid Signaling Revealed by Phosphoproteome Analysis in Arabidopsis.
    Hinano Takase, Mizuki Saigusa, Kota Yamashita, Taishi Umezawa.
      Abscisic acid (ABA) is a major phytohormone regulating plant growth and stress responses. Subclass III SnRK2 kinases and clade A type 2C protein phosphatases (PP2Cs) are core components of ABA signaling. Despite advances from phosphoproteomics, major gaps remain, particularly in mapping PP2C dephosphorylation targets and SnRK2-dependent phosphorylation dynamics under non-stress conditions. Here, we performed large-scale LC-MS/MS phosphoproteomic analyses using the subclass III SnRK2 triple mutant srk2dei and the constitutively active PP2C mutant abi1-1C, with and without ABA treatment in Arabidopsis thaliana. We identified 2757 and 2886 differentially regulated phosphopeptides in srk2dei and abi1-1C, respectively. Beyond known ABA signaling components, these datasets revealed numerous previously uncharacterized candidate proteins involved in metabolism, membrane transport, transcription, and cytoskeletal regulation. Integrative analysis uncovered a core set of candidate proteins oppositely regulated by SnRK2-mediated phosphorylation and ABI1-mediated dephosphorylation, defining a coordinated hierarchical network. These results indicate that the SnRK2-PP2C module functions not only in stress-induced ABA responses but also as a central regulator of phosphorylation homeostasis under basal conditions. This study provides a systematic framework for the global SnRK2-PP2C phosphorylation network and reframes ABA signaling as a dynamic homeostatic system.
    Keywords:  ABA; Arabidopsis thaliana; PP2C; SnRK2; phosphoproteome
    DOI:  https://doi.org/10.3390/ijms27083532
  3. Plant J. 2026 May;126(3): e70901
    PHR1 mediates rapid high light responses and acclimation to high photosynthetic activity.
    Lukas Ackermann, Agnes Fekete, Laura Schröder, Thomas Nägele, Alina J Hieber, Monika Müller, Martin J Mueller, Maria Klecker.
      Changing light intensity requires immediate metabolic adjustment which involves reprogramming of both plastidial and nuclear gene expression, but the signaling pathways behind such responses are not fully understood. Here we report that an increase in light intensity causes fluctuations of Pi levels in the chloroplasts of Arabidopsis thaliana and induces a transcriptional response mediated by the nuclear low-Pi signaling machinery involving the transcription factor PHOSPHATE STARVATION RESPONSE 1 (PHR1). Activation of PHR1 was linked to triose phosphate metabolism since the double mutant adg1 tpt-2, defective in both starch accumulation and triose phosphate export from the chloroplast, exhibited a constitutive transcriptional Pi starvation signature. Among the high light-induced target genes of PHR1, we further investigated SRG3/GDPD1, encoding an enzyme involved in phospholipid catabolism. Lipid profiling revealed pronounced changes in srg3 mutants compared with wild-type plants, including high light triggered accumulation of α-linolenic acid and reduced levels of the photoprotective carotenoid zeaxanthin. We propose that photosynthetic activity regulates the low-Pi response machinery in the nucleus in order to implement high light acclimation leading to the liberation of cellular P as well as the maintenance of membrane integrity.
    Keywords:  PHR1; SRG3/GDPD1; light acclimation; linolenic acid; phosphate starvation; photoprotection; photosynthesis; triose phosphate utilization
    DOI:  https://doi.org/10.1111/tpj.70901
  4. J Integr Plant Biol. 2026 May 05.
    Arabidopsis inositol polyphosphate kinase activities regulate COP9 deneddylation functions in phosphate homeostasis.
    Yashika Walia, Medha Noopur, Ishana Bhattacharya, Bhaskar Chandra Sahoo, Mritunjay Kasera, Naga Jyothi Pullagurla, Smritikana Dutta, Guizhen Liu, Gabriel Schaaf, Henning Jessen, Debabrata Laha, Souvik Bhattacharjee, Saikat Bhattacharjee.
      Plant Cullin RING Ubiquitin E3 ligases (CRLs) play a critical role in targeted protein degradation, essential for physiological development and stress adaptation. The deneddylase activity of the COP9 signalosome (CSN) tightly regulates the cellular balance of neddylated cullins, which is crucial for maintaining the full spectrum of CRL functions. Although selective inositol polyphosphates (InsPs) act as cofactors in plant responses that involve ubiquitylation of negative regulators, their connection to CSN-CRL activities has remained unclear. In this study, we reveal that the two Arabidopsis thaliana InsP-kinases, IPK1 and ITPK1, physically interact and orchestrate the metabolic regulation of the CSN holo-complex activity. Notably, ITPK1 deficiency lowers Nedd8 processing rates, elevates the cellular ratios of neddylated cullins, and disturbs the dissociation equilibrium of CSN5 and CUL1 from the holo-complex. These findings uncover a novel autoregulatory switch in CSN functions, governed by deneddylation activity. Furthermore, we demonstrate that the phosphate starvation response (PSR), induced in phosphate-limited wild-type plants and constitutively active in the InsP-kinase mutants, is partly regulated by reduced deneddylation rates, which affect the stability of SPX4, a key negative regulator of PSR. Pharmacological inhibition of cullin neddylation stabilizes SPX4 and impairs PSR, thereby linking CSN-CRL dynamics to phosphate sensing. Conversely, pharmacologically inhibiting CSN5 deneddylase activity causes wild-type plants to exhibit PSR phenotypes similar to those of the InsP-kinase mutants. Collectively, these results reveal that specific InsP-kinases are partly involved in modulating plant PSR by fine-tuning the coordination between CRL and CSN activities.
    Keywords:  COP9 signalosome; InsP7, deneddylation; SPX4; cullin RING ubiquitin ligase; inositol 1,3,4‐trisphosphate 5/6‐kinase 1; inositol hexakisphosphate (InsP6) kinase 1; inositol polyphosphates; phosphate homeostasis; phosphate‐starvation response; ubiquitination
    DOI:  https://doi.org/10.1111/jipb.70268
  5. Front Plant Sci. 2026 ;17 1809056
    Abscisic acid binds to an Arabidopsis thaliana phosphodiesterase and tunes its activity.
    Mateusz Kwiatkowski, Anna Kozakiewicz-Piekarz, Chuyun Bi, Aloysius Wong, Krzysztof Jaworski, Helen Irving, Chris Gehring.
      Growing evidence suggests that plant proteomes contain numerous proteins that specifically bind abscisic acid (ABA). Many of them are complex multidomain proteins where specific ABA-binding can cause biochemical and physiological changes. Here we show that the Arabidopsis thaliana K+ transporter AtKUP5 contains both a functional cytoplasmic N-terminal adenylate cyclase (AC) enabling the synthesis of 3',5'-cAMP from ATP and a C-terminal phosphodiesterase (PDE) that hydrolyses 3',5'-cAMP to 5'-AMP. We found that ABA binds in a ligand-specific manner to the catalytic center of the PDE thereby causing a reduction of 3',5'-cAMP hydrolysis in vitro. The hydrolytic activity of the PDE is ABA concentration-dependent, biphasic and requires the presence of an intact ABA-binding site similar to the one in the canonical Pyrabactin resistance 1/PYR-like/Abscisic acid receptors, with Vmax of 1.19 pmole min-1 μg-1 in the absence of ABA, increasing to 1.58 pmole min-1 μg-1 at 2 nM ABA, and decreasing to 0.75 pmole min-1 μg-1 at 50 nM ABA. These findings are therefore consistent with a direct role of ABA in PDE activity modulations and form a functional link between 3',5'-cAMP signaling and K+ flux. Furthermore, we predict that a growing number of such receptor-like proteins that specifically and directly interact with ABA will be discovered thereby uncovering complex and ancient layers of signaling and metabolic regulation.
    Keywords:  AtKUP5; abscisic acid; biphasic effect; molecular tuning; phosphodiesterase
    DOI:  https://doi.org/10.3389/fpls.2026.1809056
  6. EMBO Rep. 2026 May 02.
    Plasmodesmal closure elicits stress responses.
    Estee E Tee, Andrew Breakspear, Diana Papp, Hannah R Thomas, Catherine Walker, Annalisa Bellandi, Christine Faulkner.
      Plant cells are connected to their neighbors via plasmodesmata facilitating the exchange of nutrients and signaling molecules. During immune responses, plasmodesmata close, but how this contributes towards a full immune response is unknown. To investigate this, we develop two transgenic lines which allow to induce plasmodesmal closure independently of immune elicitors, using the over-active CALLOSE SYNTHASE3 allele icals3m and the C-terminus of PDLP1 to drive callose deposition at plasmodesmata. Induction of plasmodesmal closure increases the expression of stress responsive genes, salicylic acid accumulation and resistance to Pseudomonas syringae DC3000. More homogeneous plasmodesmal closure using icals3m also leads to the accumulation of starch and sugars, decreases leaf growth, as well as hypersusceptibility to Botrytis cinerea. Based on the profile of responses, we conclude that plasmodesmal closure activates stress signaling, raising questions about the signals mediating this response and whether these responses occur in all circumstances when plasmodesmata close.
    DOI:  https://doi.org/10.1038/s44319-026-00789-2
  7. Nat Plants. 2026 May 06.
    Cell-type-specific autophagy in root-hair-forming cells is essential for salt stress tolerance in Arabidopsis thaliana.
    Jierui Zhao, Peng Gao, Sunhuan Xiang, Christian Löfke, Kai Ching Yeung, Yixuan Chen, Liwen Jiang, Yasin Dagdas.
      Autophagy is a vital cellular quality control pathway that maintains cellular homoeostasis under changing environments. While the organismal phenotypes of autophagy-deficient plants under stress are well characterized, the contribution of cell-type-specific autophagy responses to whole-plant homoeostasis remains poorly understood. Here we show that root-hair-forming cells (trichoblasts) in Arabidopsis thaliana exhibit higher autophagic flux than adjacent non-hair cells (atrichoblasts). This differential autophagy is genetically linked to cell fate determination during early development. Mutants with disrupted trichoblast or atrichoblast identity lose the autophagy distinction between these cell types. Functional analyses reveal that elevated autophagy in trichoblasts is essential for sodium ion sequestration in vacuoles-a key mechanism for salt stress tolerance. Disrupting autophagy specifically in trichoblasts impairs sodium accumulation and reduces plant survival under salt stress. Conversely, cell-type-specific complementation restores both sodium sequestration and stress tolerance. Our findings uncover a cell-type-specific autophagy program in root hairs and demonstrate how developmental cues shape autophagy to enhance stress resilience. This work establishes a direct link between cell identity, autophagy and environmental adaptation in plants.
    DOI:  https://doi.org/10.1038/s41477-026-02285-w
  8. Plant Physiol. 2026 May 06. pii: kiag265. [Epub ahead of print]
    StWRKY46 promotes stomatal closure and enhances potato drought tolerance by mediating the PYL1-ABI2-OST1/SnRK2.5/SnRK2.6 pathway.
    Han Wei, Xiao Wang, Shigui Li, Ning Zhang, Huaijun Si.
      Drought stress affects crop yield and quality. Abscisic acid (ABA) plays a crucial role in plant responses to drought stress; however, the signal transduction mechanism in potato (Solanum tuberosum L.) remains unclear. This study identifies a WRKY transcription factor (TF) member, StWRKY46, that enhances drought tolerance in potato. Under drought, StWRKY46 binds directly to the promoter of StPYL1 (a PYR/PYL family ABA receptor) and activates its transcription, triggering the ABA signaling pathway and improving drought tolerance in potato. StPYL1 interacts with StHAB1, StPP2C24, StPP2C51.1, and StABI2. StABI2 acts as a key negative regulator of ABA signaling. It interacts with StOST1, StSnRK2.5, and StSnRK2.6 to regulate the expression of stomatal movement-related genes, including the slow-type anion channel 1 (StSLAC1) and guard cell hydrogen peroxide-resistant 1 (StGHR1), thereby potentiating ABA-induced stomatal closure. Overall, our findings demonstrate the molecular mechanism of StWRKY46-mediated drought tolerance through the ABA-StPYL1-StABI2-StOST1/StSnRK2.5/StSnRK2.6 pathway in potato.
    Keywords:  ABA signal transduction; WRKY transcription factor; drought; potato; stomatal movement
    DOI:  https://doi.org/10.1093/plphys/kiag265
This page is being maintained by Thomas Krichel. It was last updated on 2026‒06‒12 at 9:45.