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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.


ABA-induced interaction between PYL1 and ABI1. The gate (magenta) and latch (blue) loops contact the β-hairpin of ABI1 (yellow), which also indirectly interacts with ABA mediated by a water molecule (cyan). This figure was created using PDB coordinates of the complex of ABA-bound PYL1 and ABI1 (3JRQ).
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f4-7_123: ABA-induced interaction between PYL1 and ABI1. The gate (magenta) and latch (blue) loops contact the β-hairpin of ABI1 (yellow), which also indirectly interacts with ABA mediated by a water molecule (cyan). This figure was created using PDB coordinates of the complex of ABA-bound PYL1 and ABI1 (3JRQ).

Mentions: The inhibitory mechanism of the ABA-bound receptors is well defined by the structure of the ternary complex with PP2Cs9,10,13. Figure 4 shows the interface between PYL1 and ABI1, a PP2C family member in Arabidopsis. The β-hairpin of ABI1 provides the major binding interface with the ABA-bound PYL110. There are two crucial residues for binding the closed gate and latch loops of the receptor. W300 inserts its indole ring between the two closed loops of the ABA-bound receptor. The indole imine group forms a water-mediated hydrogen bond with the two closed loops and the carbonyl group of ABA. In addition, R304 seems to hold down the gate loop of the receptor by stacking between its guanidinium group and P115 on the loop of PYL1. These interactions further lock the gate loop in the closed conformation, which properly situates the gate loop into the active site of PP2C.


Regulatory mechanism of abscisic acid signaling
ABA-induced interaction between PYL1 and ABI1. The gate (magenta) and latch (blue) loops contact the β-hairpin of ABI1 (yellow), which also indirectly interacts with ABA mediated by a water molecule (cyan). This figure was created using PDB coordinates of the complex of ABA-bound PYL1 and ABI1 (3JRQ).
© Copyright Policy
Related In: Results  -  Collection

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

f4-7_123: ABA-induced interaction between PYL1 and ABI1. The gate (magenta) and latch (blue) loops contact the β-hairpin of ABI1 (yellow), which also indirectly interacts with ABA mediated by a water molecule (cyan). This figure was created using PDB coordinates of the complex of ABA-bound PYL1 and ABI1 (3JRQ).
Mentions: The inhibitory mechanism of the ABA-bound receptors is well defined by the structure of the ternary complex with PP2Cs9,10,13. Figure 4 shows the interface between PYL1 and ABI1, a PP2C family member in Arabidopsis. The β-hairpin of ABI1 provides the major binding interface with the ABA-bound PYL110. There are two crucial residues for binding the closed gate and latch loops of the receptor. W300 inserts its indole ring between the two closed loops of the ABA-bound receptor. The indole imine group forms a water-mediated hydrogen bond with the two closed loops and the carbonyl group of ABA. In addition, R304 seems to hold down the gate loop of the receptor by stacking between its guanidinium group and P115 on the loop of PYL1. These interactions further lock the gate loop in the closed conformation, which properly situates the gate loop into the active site of PP2C.

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.