The Wheat Intrinsically Disordered Protein <i>Td</i>RL1 Negatively Regulates the Type One Protein Phosphatase <i>Td</i>PP1

The Wheat Intrinsically Disordered Protein <i>Td</i>RL1 Negatively Regulates the Type One Protein Phosphatase <i>Td</i>PP1

Type 1 protein phosphatases (PP1s) are crucial in various plant cellular processes. Their function is controlled by regulators known as PP1-interacting proteins (PIPs), often intrinsically disordered, such as Inhibitor 2 (I2), conserved across kingdoms. The durum wheat <i>Td</i>RL1 acts...

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Bibliographic Details
Main Authors: Fatma Amor, Mariem Bradai, Ikram Zaidi, Vitor Amorim-Silva, Nabil Miled, Moez Hanin, Chantal Ebel
Format: Article
Language:English
Published: MDPI AG 2025-04-01
Series:Biomolecules
Subjects:
PP1
<i>Td</i>RL1
phosphatase activity
PP1-interacting proteins
three-dimensional structure prediction
Online Access:https://www.mdpi.com/2218-273X/15/5/631
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Summary:Type 1 protein phosphatases (PP1s) are crucial in various plant cellular processes. Their function is controlled by regulators known as PP1-interacting proteins (PIPs), often intrinsically disordered, such as Inhibitor 2 (I2), conserved across kingdoms. The durum wheat <i>Td</i>RL1 acts as a positive regulator of plant stress tolerance, presumably by inhibiting PP1 activity. In this work, co-immunoprecipitation and bimolecular fluorescence complementation (BiFC) assays demonstrate that the durum wheat <i>Td</i>PP1 interacts with both <i>Td</i>RL1 and <i>At</i>-I2 in vivo. YFP fluorescence restored after <i>Td</i>RL1-<i>Td</i>PP1 interaction decorated specifically the microtubular network of the tobacco co-infiltrated cells. In vitro phosphatase assays revealed that <i>Td</i>RL1 inhibited the activity of wild-type <i>Td</i>PP1 and two mutant forms (T243M and H135A) in a concentration-dependent manner, showing a novel and potent inhibition mechanism. Structural modeling of the <i>Td</i>PP1-inhibitor complexes suggested that both <i>At</i>-I2 and <i>Td</i>RL1 bind to <i>Td</i>PP1 by wrapping their flexible C-terminal tails around it, blocking access to the active site. Remarkably, the model showed that <i>Td</i>RL1 differs from <i>At</i>-I2 in its interaction with <i>Td</i>PP1 by trapping the phosphatase with its N-terminal tail. These findings provide important insights into the regulatory mechanisms governing the activity of PP1s in plants and highlight the potential for targeted inhibition to modulate plant stress responses.
ISSN:2218-273X

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