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Regulatory mechanism of abscisic acid signaling

View Article: PubMed Central - PubMed

ABSTRACT

Abscisic acid (ABA) is a major phytohormone that mediates the adaptation of plants to environmental stresses such as drought and regulates developmental signals such as seed maturation. Studies on ABA signaling have progressed rapidly since the recent discovery of PYR/PYL receptor proteins as soluble ABA receptors. In plant cells, the receptor receives ABA to inhibit the phosphatase activity of type 2C protein phosphatase (PP2C), which is the major negative regulator in ABA signaling. SNF1-related protein kinase 2 (SnRK2) is then released from negative regulation by PP2C, turning on ABA signals by the phosphorylation of downstream factors. Insights into the regulation of PYR/PYL receptor proteins is therefore required in order to control drought-stress tolerance in plants. This article reviews the regulatory mechanism of the ABA receptor by ABA and its selective agonist. Structural analyses of PYR/PYL receptors have clearly elucidated the mechanism of ABA perception of the receptor or the mechanism of interaction with PP2C that leads to inhibition of its phosphatase activity. Moreover, the structures of PYR/PYL receptors complexed with pyrabactin, a selective ABA agonist, have provided the structural basis of ABA agonism and antagonism.

No MeSH data available.


Schematic diagram of a double-negative regulation system in ABA signaling.
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f1-7_123: Schematic diagram of a double-negative regulation system in ABA signaling.

Mentions: The core components form the signaling complex, which offers a double-negative regulation system in ABA signaling (Fig. 1)17. Normally, PP2C inactivates SnRK2 by dephosphorylation and the ABA signals are silent. Once ABA is induced by environmental conditions or developmental cues, the ABA-bound PYR/PYL receptor interacts with PP2C and inhibits its phosphatase activity. SnRK2 is then released from negative regulation by PP2C, turning on ABA signals by the phosphorylation of downstream factors such as AREB/ABF bZIP transcription factors, SLAC1 slow anion channels, and others. Phosphorylated AREB/ABF activates numerous downstream genes in response to water stress, including many late embryogenesis abundant (LEA) class genes and other transcription factors18. SLAC1, which has a central role in guard cells, induces rapid stomatal closure to prevent water loss by perspiration19,20. Therefore, the ABA signaling pathway consists of just four steps to gene expression or another output, and its switching point is ABA perception of the PYR/PYL receptor.


Regulatory mechanism of abscisic acid signaling
Schematic diagram of a double-negative regulation system in ABA signaling.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC5036775&req=5

f1-7_123: Schematic diagram of a double-negative regulation system in ABA signaling.
Mentions: The core components form the signaling complex, which offers a double-negative regulation system in ABA signaling (Fig. 1)17. Normally, PP2C inactivates SnRK2 by dephosphorylation and the ABA signals are silent. Once ABA is induced by environmental conditions or developmental cues, the ABA-bound PYR/PYL receptor interacts with PP2C and inhibits its phosphatase activity. SnRK2 is then released from negative regulation by PP2C, turning on ABA signals by the phosphorylation of downstream factors such as AREB/ABF bZIP transcription factors, SLAC1 slow anion channels, and others. Phosphorylated AREB/ABF activates numerous downstream genes in response to water stress, including many late embryogenesis abundant (LEA) class genes and other transcription factors18. SLAC1, which has a central role in guard cells, induces rapid stomatal closure to prevent water loss by perspiration19,20. Therefore, the ABA signaling pathway consists of just four steps to gene expression or another output, and its switching point is ABA perception of the PYR/PYL receptor.

View Article: PubMed Central - PubMed

ABSTRACT

Abscisic acid (ABA) is a major phytohormone that mediates the adaptation of plants to environmental stresses such as drought and regulates developmental signals such as seed maturation. Studies on ABA signaling have progressed rapidly since the recent discovery of PYR/PYL receptor proteins as soluble ABA receptors. In plant cells, the receptor receives ABA to inhibit the phosphatase activity of type 2C protein phosphatase (PP2C), which is the major negative regulator in ABA signaling. SNF1-related protein kinase 2 (SnRK2) is then released from negative regulation by PP2C, turning on ABA signals by the phosphorylation of downstream factors. Insights into the regulation of PYR/PYL receptor proteins is therefore required in order to control drought-stress tolerance in plants. This article reviews the regulatory mechanism of the ABA receptor by ABA and its selective agonist. Structural analyses of PYR/PYL receptors have clearly elucidated the mechanism of ABA perception of the receptor or the mechanism of interaction with PP2C that leads to inhibition of its phosphatase activity. Moreover, the structures of PYR/PYL receptors complexed with pyrabactin, a selective ABA agonist, have provided the structural basis of ABA agonism and antagonism.

No MeSH data available.