ABA Signaling Pathway - Revision history

Alice Harmon at 18:07, 8 October 2013

2013-10-08T18:07:19Z

← Older revision		Revision as of 18:07, 8 October 2013
Line 1:		Line 1:
	[[Image:ABA model 2 med.jpg\|left]]		[[Image:ABA model 2 med.jpg\|left]]

	Abscisic acid (ABA,)[[Image:Abscisic acid.svg.png\|thumb\| Abscisic Acid]] is a plant hormone that regulates seed development, dormancy and germination, stomatal closure, and responses to drought stress, and its core signaling pathway has recently been identified.<ref>PMID:15012233</ref><ref>PMID:12045268</ref><ref>PMID:20192755</ref> In Arabidopsis, this pathway involves families of ABA receptors (PYR1/RCAR11, PYL1/RCAR12, PYL2/RCAR14, PYL3/RCAR13, PYL8/RCAR3, PYL9/RCAR1)<ref name = "Ma2009">PMID:19407143</ref><ref name = "Melcher2009">PMID:19898420</ref><ref name = "Park2009" >PMID:19407142</ref><ref name = Zhang2012>PMID:22579247</ref><ref>PMID:23370718</ref>, protein phosphatase 2Cs (ABI1, ABI2, HAB1, HAB2, PP2CA/AHG3)<ref name = "Ma2009"/><ref name = "Park2009"/><ref>PMID:16339800</ref>, and SNRK2 protein kinases (SnRK2.6/OST1/SRK2E, SNRK2.2/SRK2D and SnRK2.3/SRK2IA)<ref name = "Mustilli2002">PMID:12468729</ref><ref>PMID:12514244</ref><ref name = "Nakashima2009">PMID:19541597</ref><ref name = "Fujii2007">PMID:17307925</ref>.		Abscisic acid (ABA,)[[Image:Abscisic acid.svg.png\|thumb\| Abscisic Acid]] is a plant hormone that regulates seed development, dormancy and germination, stomatal closure, and responses to drought stress, and its core signaling pathway has recently been identified.<ref>PMID:15012233</ref><ref>PMID:12045268</ref><ref>PMID:20192755</ref> In Arabidopsis, this pathway involves families of ABA receptors (PYR1/RCAR11, PYL1/RCAR12, PYL2/RCAR14, PYL3/RCAR13, PYL8/RCAR3, PYL9/RCAR1)<ref name = "Ma2009">PMID:19407143</ref><ref name = "Melcher2009">PMID:19898420</ref><ref name = "Park2009" >PMID:19407142</ref><ref name = Zhang2012>PMID:22579247</ref><ref>PMID:23370718</ref>, protein phosphatase 2Cs (ABI1, ABI2, HAB1, HAB2, PP2CA/AHG3)<ref name = "Ma2009"/><ref name = "Park2009"/><ref name = Santiago 2009">PMID:19624469</ref><ref>PMID:16339800</ref>, and SNRK2 protein kinases (SnRK2.6/OST1/SRK2E, SNRK2.2/SRK2D and SnRK2.3/SRK2IA)<ref name = "Mustilli2002">PMID:12468729</ref><ref>PMID:12514244</ref><ref name = "Nakashima2009">PMID:19541597</ref><ref name = "Fujii2007">PMID:17307925</ref>.

	The core ABA signaling pathway is shown in the figure to the left. In unstimulated cells, the ABA receptor (R) is an unliganded dimer<ref name = "Melcher2009"/><ref>PMID:19933100</ref><ref>PMID:23265948</ref><ref name = "Zhang2012"/> (monomer shown) in the cytosol and nucleus, and the SNRK2 protein kinase (K) is bound to a protein phosphatase 2C (P) in a complex (K-P) in which the kinase is dephosphorylated and inactivated by the phosphatase. When the ABA level rises, ABA binds to the ABA receptor<ref name = "Ma2009"/><ref name = "Park2009"/><ref>PMID:19893533</ref>, and this creates a binding surface for PP2C. The activated receptor (R<sup>.</sup>ABA) dissociates to monomers which bind to protein phosphatase 2C<ref~~>PMID:19624469<~~/~~ref~~> (R<sup>.</sup>ABA-P). The sequestration of the protein phosphatase frees the protein kinase to be activated by autophosphorylation or phosphorylation by another protein kinase. Activation of SnRK2.6/OST1/SRK2E leads to phosphorylation of: 1) ion channels SLAC1<ref>PMID: 19955405</ref> and KAT1<ref>PMID:19785574</ref> in guard cells and stomatal closure; 2) transcription factor ABI5<ref name = "Nakashima2009"/> in seeds/seedlings and dormancy/growth arrest; or 3) phosphorylation of transcription factor AREB/ABF <ref>PMID: 16446457</ref><ref name = "Fujii2007"/> in vegetative tissue and stress tolerance and growth regulation.		The core ABA signaling pathway is shown in the figure to the left. In unstimulated cells, the ABA receptor (R) is an unliganded dimer<ref name = "Melcher2009"/><ref>PMID:19933100</ref><ref>PMID:23265948</ref><ref name = "Zhang2012"/> (monomer shown) in the cytosol and nucleus, and the SNRK2 protein kinase (K) is bound to a protein phosphatase 2C (P) in a complex (K-P) in which the kinase is dephosphorylated and inactivated by the phosphatase. When the ABA level rises, ABA binds to the ABA receptor<ref name = "Ma2009"/><ref name = "Park2009"/><ref>PMID:19893533</ref>, and this creates a binding surface for PP2C. The activated receptor (R<sup>.</sup>ABA) dissociates to monomers which bind to protein phosphatase 2C<ref name = Santiago 2009"/> (R<sup>.</sup>ABA-P). The sequestration of the protein phosphatase frees the protein kinase to be activated by autophosphorylation or phosphorylation by another protein kinase. Activation of SnRK2.6/OST1/SRK2E leads to phosphorylation of: 1) ion channels SLAC1<ref>PMID: 19955405</ref> and KAT1<ref>PMID:19785574</ref> in guard cells and stomatal closure; 2) transcription factor ABI5<ref name = "Nakashima2009"/> in seeds/seedlings and dormancy/growth arrest; or 3) phosphorylation of transcription factor AREB/ABF <ref>PMID: 16446457</ref><ref name = "Fujii2007"/> in vegetative tissue and stress tolerance and growth regulation.

	Structures in the figure are: R, apo PYL2, [[3kdh]]; R<sup>.</sup>ABA, PYL2<sup>.</sup>ABA, [[3kdi]]; K-P; SnRK2.6-HAB1, [[3ujg]]; R<sup>.</sup>ABA-P, PYL2<sup>.</sup>ABA-ABI2, [[3ujl]]; K, SnRK2.6,[[3uc4]].		Structures in the figure are: R, apo PYL2, [[3kdh]]; R<sup>.</sup>ABA, PYL2<sup>.</sup>ABA, [[3kdi]]; K-P; SnRK2.6-HAB1, [[3ujg]]; R<sup>.</sup>ABA-P, PYL2<sup>.</sup>ABA-ABI2, [[3ujl]]; K, SnRK2.6,[[3uc4]].

Alice Harmon at 22:23, 5 October 2013

2013-10-05T22:23:34Z

← Older revision		Revision as of 22:23, 5 October 2013
Line 1:		Line 1:
	[[Image:ABA model 2 med.jpg\|left]]		[[Image:ABA model 2 med.jpg\|left]]

	Abscisic acid (ABA,)[[Image:Abscisic acid.svg.png\|thumb\| Abscisic Acid]] is a plant hormone that regulates seed development, dormancy and germination, stomatal closure, and responses to drought stress, and its core signaling pathway has recently been identified.<ref>PMID:15012233</ref><ref>PMID:12045268</ref><ref>PMID:20192755</ref> In Arabidopsis, this pathway involves families of ABA receptors (PYR1/RCAR11, PYL1/RCAR12, PYL2/RCAR14, PYL3/RCAR13, PYL8/RCAR3, PYL9/RCAR1)<ref name = "Ma2009">PMID:19407143</ref><ref name = "Melcher2009">PMID:19898420</ref><ref name = "Park2009" >PMID:19407142</ref><ref name = Zhang2012>PMID:22579247</ref><ref>PMID:23370718</ref>, protein phosphatase 2Cs (ABI1, ABI2, HAB1, HAB2, PP2CA/AHG3)<ref name = "Ma2009"/><ref name = "Park2009"/><ref>PMID:16339800</ref>, SNRK2 protein kinases (SnRK2.6/OST1/SRK2E, SNRK2.2/SRK2D and SnRK2.3/SRK2IA)<ref name = "Mustilli2002">PMID:12468729</ref><ref>PMID:12514244</ref><ref name = "Nakashima2009">PMID:19541597</ref><ref name = "Fujii2007">PMID:17307925</ref>.		Abscisic acid (ABA,)[[Image:Abscisic acid.svg.png\|thumb\| Abscisic Acid]] is a plant hormone that regulates seed development, dormancy and germination, stomatal closure, and responses to drought stress, and its core signaling pathway has recently been identified.<ref>PMID:15012233</ref><ref>PMID:12045268</ref><ref>PMID:20192755</ref> In Arabidopsis, this pathway involves families of ABA receptors (PYR1/RCAR11, PYL1/RCAR12, PYL2/RCAR14, PYL3/RCAR13, PYL8/RCAR3, PYL9/RCAR1)<ref name = "Ma2009">PMID:19407143</ref><ref name = "Melcher2009">PMID:19898420</ref><ref name = "Park2009" >PMID:19407142</ref><ref name = Zhang2012>PMID:22579247</ref><ref>PMID:23370718</ref>, protein phosphatase 2Cs (ABI1, ABI2, HAB1, HAB2, PP2CA/AHG3)<ref name = "Ma2009"/><ref name = "Park2009"/><ref>PMID:16339800</ref>, and SNRK2 protein kinases (SnRK2.6/OST1/SRK2E, SNRK2.2/SRK2D and SnRK2.3/SRK2IA)<ref name = "Mustilli2002">PMID:12468729</ref><ref>PMID:12514244</ref><ref name = "Nakashima2009">PMID:19541597</ref><ref name = "Fujii2007">PMID:17307925</ref>.

	The core ABA signaling pathway is shown in the figure to the left. In unstimulated cells, the ABA receptor (R) is an unliganded dimer<ref name = "Melcher2009"/><ref>PMID:19933100</ref><ref>PMID:23265948</ref><ref name = "Zhang2012"/> (monomer shown) in the cytosol and nucleus, and the SNRK2 protein kinase (K) is bound to a protein phosphatase 2C (P) in a complex (K-P) in which the kinase is dephosphorylated and inactivated by the phosphatase. When the ABA level rises, ABA binds to the ABA receptor<ref name = "Ma2009"/><ref name = "Park2009"/><ref>PMID:19893533</ref>, and this creates a binding surface for PP2C. The activated receptor (R<sup>.</sup>ABA) dissociates to monomers which bind to protein phosphatase 2C<ref>PMID:19624469</ref> (R<sup>.</sup>ABA-P). The sequestration of the protein phosphatase frees the protein kinase to be activated by autophosphorylation or phosphorylation by another protein kinase. Activation of SnRK2.6/OST1/SRK2E leads to phosphorylation of: 1) ion channels SLAC1<ref>PMID: 19955405</ref> and KAT1<ref>PMID:19785574</ref> in guard cells and stomatal closure; 2) transcription factor ABI5<ref name = "Nakashima2009"/> in seeds/seedlings and dormancy/growth arrest; or 3) phosphorylation of transcription factor AREB/ABF <ref>PMID: 16446457</ref><ref name = "Fujii2007"/> in vegetative tissue and stress tolerance and growth regulation.		The core ABA signaling pathway is shown in the figure to the left. In unstimulated cells, the ABA receptor (R) is an unliganded dimer<ref name = "Melcher2009"/><ref>PMID:19933100</ref><ref>PMID:23265948</ref><ref name = "Zhang2012"/> (monomer shown) in the cytosol and nucleus, and the SNRK2 protein kinase (K) is bound to a protein phosphatase 2C (P) in a complex (K-P) in which the kinase is dephosphorylated and inactivated by the phosphatase. When the ABA level rises, ABA binds to the ABA receptor<ref name = "Ma2009"/><ref name = "Park2009"/><ref>PMID:19893533</ref>, and this creates a binding surface for PP2C. The activated receptor (R<sup>.</sup>ABA) dissociates to monomers which bind to protein phosphatase 2C<ref>PMID:19624469</ref> (R<sup>.</sup>ABA-P). The sequestration of the protein phosphatase frees the protein kinase to be activated by autophosphorylation or phosphorylation by another protein kinase. Activation of SnRK2.6/OST1/SRK2E leads to phosphorylation of: 1) ion channels SLAC1<ref>PMID: 19955405</ref> and KAT1<ref>PMID:19785574</ref> in guard cells and stomatal closure; 2) transcription factor ABI5<ref name = "Nakashima2009"/> in seeds/seedlings and dormancy/growth arrest; or 3) phosphorylation of transcription factor AREB/ABF <ref>PMID: 16446457</ref><ref name = "Fujii2007"/> in vegetative tissue and stress tolerance and growth regulation.

Alice Harmon at 17:09, 5 October 2013

2013-10-05T17:09:48Z

← Older revision		Revision as of 17:09, 5 October 2013
Line 1:		Line 1:
	[[Image:ABA model 2 med.jpg\|left]]		[[Image:ABA model 2 med.jpg\|left]]

	Abscisic acid (ABA,)[[Image:Abscisic acid.svg.png\|thumb\| Abscisic Acid]] is a plant hormone that regulates seed development, dormancy and germination, stomatal closure, and responses to drought stress, and its core signaling pathway has recently been identified.<ref>PMID:15012233</ref><ref>PMID:12045268</ref><ref>PMID:20192755</ref> In Arabidopsis, this pathway involves families of ABA receptors (PYR1/RCAR11, PYL1/RCAR12, PYL2/RCAR14, PYL3/RCAR13, PYL8/RCAR3, PYL9/RCAR1)<ref>PMID:19407143</ref><ref>PMID:19407142</ref><ref>"PMID:22579247</ref><ref>PMID:23370718</ref>, protein phosphatase 2Cs (ABI1, ABI2, HAB1, HAB2, PP2CA/AHG3)<ref~~>PMID:19407143<~~/~~ref~~><ref~~>PMID:19407142<~~/~~ref~~><ref>PMID:16339800</ref>, SNRK2 protein kinases (SnRK2.6/OST1/SRK2E, SNRK2.2/SRK2D and SnRK2.3/SRK2IA)<ref name = "Mustilli2002">PMID:12468729</ref><ref>PMID:12514244</ref><ref name = "Nakashima2009">PMID:19541597</ref><ref name = "Fujii2007">PMID:17307925</ref>.		Abscisic acid (ABA,)[[Image:Abscisic acid.svg.png\|thumb\| Abscisic Acid]] is a plant hormone that regulates seed development, dormancy and germination, stomatal closure, and responses to drought stress, and its core signaling pathway has recently been identified.<ref>PMID:15012233</ref><ref>PMID:12045268</ref><ref>PMID:20192755</ref> In Arabidopsis, this pathway involves families of ABA receptors (PYR1/RCAR11, PYL1/RCAR12, PYL2/RCAR14, PYL3/RCAR13, PYL8/RCAR3, PYL9/RCAR1)<ref name = "Ma2009">PMID:19407143</ref><ref name = "Melcher2009">PMID:19898420</ref><ref name = "Park2009" >PMID:19407142</ref><ref name = Zhang2012>PMID:22579247</ref><ref>PMID:23370718</ref>, protein phosphatase 2Cs (ABI1, ABI2, HAB1, HAB2, PP2CA/AHG3)<ref name = "Ma2009"/><ref name = "Park2009"/><ref>PMID:16339800</ref>, SNRK2 protein kinases (SnRK2.6/OST1/SRK2E, SNRK2.2/SRK2D and SnRK2.3/SRK2IA)<ref name = "Mustilli2002">PMID:12468729</ref><ref>PMID:12514244</ref><ref name = "Nakashima2009">PMID:19541597</ref><ref name = "Fujii2007">PMID:17307925</ref>.

	The core ABA signaling pathway is shown in the figure to the left. In unstimulated cells, the ABA receptor (R) is an unliganded dimer<ref~~>PMID:19898420<~~/~~ref~~><ref>PMID:19933100</ref><ref>PMID:23265948</ref><ref>"~~PMID:22579247<~~/~~ref~~> (monomer shown) in the cytosol and nucleus, and the SNRK2 protein kinase (K) is bound to a protein phosphatase 2C (P) in a complex (K-P) in which the kinase is dephosphorylated and inactivated by the phosphatase. When the ABA level rises, ABA binds to the ABA receptor<ref~~>PMID:19893533<~~/~~ref~~><ref~~>PMID:19407143<~~/~~ref~~><ref>PMID:~~19407142~~</ref>, and this creates a binding surface for PP2C. The activated receptor (R<sup>.</sup>ABA) dissociates to monomers which bind to protein phosphatase 2C<ref>PMID:19624469</ref> (R<sup>.</sup>ABA-P). The sequestration of the protein phosphatase frees the protein kinase to be activated by autophosphorylation or phosphorylation by another protein kinase. Activation of SnRK2.6/OST1/SRK2E leads to phosphorylation of: 1) ion channels SLAC1<ref>PMID: 19955405</ref> and KAT1<ref>PMID:19785574</ref> in guard cells and stomatal closure; 2) transcription factor ABI5<ref name = "Nakashima2009"/> in seeds/seedlings and dormancy/growth arrest; or 3) phosphorylation of transcription factor AREB/ABF <ref>PMID: 16446457</ref><ref name = "Fujii2007"/> in vegetative tissue and stress tolerance and growth regulation.		The core ABA signaling pathway is shown in the figure to the left. In unstimulated cells, the ABA receptor (R) is an unliganded dimer<ref name = "Melcher2009"/><ref>PMID:19933100</ref><ref>PMID:23265948</ref><ref name = "Zhang2012"/> (monomer shown) in the cytosol and nucleus, and the SNRK2 protein kinase (K) is bound to a protein phosphatase 2C (P) in a complex (K-P) in which the kinase is dephosphorylated and inactivated by the phosphatase. When the ABA level rises, ABA binds to the ABA receptor<ref name = "Ma2009"/><ref name = "Park2009"/><ref>PMID:19893533</ref>, and this creates a binding surface for PP2C. The activated receptor (R<sup>.</sup>ABA) dissociates to monomers which bind to protein phosphatase 2C<ref>PMID:19624469</ref> (R<sup>.</sup>ABA-P). The sequestration of the protein phosphatase frees the protein kinase to be activated by autophosphorylation or phosphorylation by another protein kinase. Activation of SnRK2.6/OST1/SRK2E leads to phosphorylation of: 1) ion channels SLAC1<ref>PMID: 19955405</ref> and KAT1<ref>PMID:19785574</ref> in guard cells and stomatal closure; 2) transcription factor ABI5<ref name = "Nakashima2009"/> in seeds/seedlings and dormancy/growth arrest; or 3) phosphorylation of transcription factor AREB/ABF <ref>PMID: 16446457</ref><ref name = "Fujii2007"/> in vegetative tissue and stress tolerance and growth regulation.

	Structures in the figure are: R, apo PYL2, [[3kdh]]; R<sup>.</sup>ABA, PYL2<sup>.</sup>ABA, [[3kdi]]; K-P; SnRK2.6-HAB1, [[3ujg]]; R<sup>.</sup>ABA-P, PYL2<sup>.</sup>ABA-ABI2, [[3ujl]]; K, SnRK2.6,[[3uc4]].		Structures in the figure are: R, apo PYL2, [[3kdh]]; R<sup>.</sup>ABA, PYL2<sup>.</sup>ABA, [[3kdi]]; K-P; SnRK2.6-HAB1, [[3ujg]]; R<sup>.</sup>ABA-P, PYL2<sup>.</sup>ABA-ABI2, [[3ujl]]; K, SnRK2.6,[[3uc4]].

	For ~~further information~~ about proteins involved in this pathway see [[PYR/PYL/RCAR family of ABA receptors]], [[ABA-regulated Protein Phosphatase 2C]], [[ABA-regulated SNRK2 Protein Kinase]].		==Structures of Proteins==
			For details about the structures of proteins involved in this pathway see [[PYR/PYL/RCAR family of ABA receptors]], [[ABA-regulated Protein Phosphatase 2C]], [[ABA-regulated SNRK2 Protein Kinase]].

	==References==		==References==

Alice Harmon at 16:36, 5 October 2013

2013-10-05T16:36:24Z

← Older revision		Revision as of 16:36, 5 October 2013
Line 1:		Line 1:
	[[Image:ABA model 2 med.jpg\|left]]		[[Image:ABA model 2 med.jpg\|left]]

	Abscisic acid (ABA,)[[Image:Abscisic acid.svg.png\|thumb\| Abscisic Acid]] is a plant hormone that regulates seed development, dormancy and germination, stomatal closure, and responses to drought stress, and its core signaling pathway has recently been identified.<ref>PMID:15012233</ref><ref>PMID:12045268</ref><ref>PMID:20192755</ref> In Arabidopsis, this pathway involves families of ABA receptors (PYR1/RCAR11, PYL1/RCAR12, PYL2/RCAR14, PYL3/RCAR13, PYL8/RCAR3, PYL9/RCAR1)<ref>PMID:19407143</ref><ref>PMID:19407142</ref><ref>"PMID:22579247</ref><ref>PMID:23370718</ref>, protein phosphatase 2Cs (ABI1, ABI2, HAB1, HAB2, PP2CA/AHG3)<ref>PMID:19407143</ref><ref>PMID:19407142</ref><ref>PMID:16339800</ref>, SNRK2 protein kinases ([[SnRK2.6/OST1/SRK2E]], SNRK2.2/SRK2D and SnRK2.3/SRK2IA).<ref name = "Mustilli2002">PMID:12468729</ref><ref>PMID:12514244</ref><ref name = "Nakashima2009">PMID:19541597</ref><ref name = "Fujii2007">PMID:17307925</ref>		Abscisic acid (ABA,)[[Image:Abscisic acid.svg.png\|thumb\| Abscisic Acid]] is a plant hormone that regulates seed development, dormancy and germination, stomatal closure, and responses to drought stress, and its core signaling pathway has recently been identified.<ref>PMID:15012233</ref><ref>PMID:12045268</ref><ref>PMID:20192755</ref> In Arabidopsis, this pathway involves families of ABA receptors (PYR1/RCAR11, PYL1/RCAR12, PYL2/RCAR14, PYL3/RCAR13, PYL8/RCAR3, PYL9/RCAR1)<ref>PMID:19407143</ref><ref>PMID:19407142</ref><ref>"PMID:22579247</ref><ref>PMID:23370718</ref>, protein phosphatase 2Cs (ABI1, ABI2, HAB1, HAB2, PP2CA/AHG3)<ref>PMID:19407143</ref><ref>PMID:19407142</ref><ref>PMID:16339800</ref>, SNRK2 protein kinases (SnRK2.6/OST1/SRK2E, SNRK2.2/SRK2D and SnRK2.3/SRK2IA)<ref name = "Mustilli2002">PMID:12468729</ref><ref>PMID:12514244</ref><ref name = "Nakashima2009">PMID:19541597</ref><ref name = "Fujii2007">PMID:17307925</ref>.

	The core ABA signaling pathway is shown in the figure to the left. In unstimulated cells, the ABA receptor (R) is an unliganded dimer<ref>PMID:19898420</ref><ref>PMID:19933100</ref><ref>PMID:23265948</ref><ref>"PMID:22579247</ref> (monomer shown) in the cytosol and nucleus, and the SNRK2 protein kinase (K) is bound to a protein phosphatase 2C (P) in a complex (K-P) in which the kinase is dephosphorylated and inactivated by the phosphatase. When the ABA level rises ABA binds to the ABA receptor<ref>PMID:19893533</ref><ref>PMID:19407143</ref><ref>PMID:19407142</ref>, and this creates a binding surface for PP2C. The activated receptor (R<sup>.</sup>ABA) dissociates to monomers which bind to protein phosphatase 2C<ref>PMID:19624469</ref> (R<sup>.</sup>ABA-P). The sequestration of the protein phosphatase frees the protein kinase to be activated by autophosphorylation or phosphorylation by another protein kinase. Activation of SnRK2.6/OST1/SRK2E leads to phosphorylation of: 1) ion channels SLAC1<ref>PMID: 19955405</ref> and KAT1<ref>PMID:19785574</ref> in guard cells and stomatal closure; 2) transcription factor ABI5<ref name = "Nakashima2009"/> in seeds/seedlings and dormancy/growth arrest; or 3) phosphorylation of transcription factor AREB/ABF <ref>PMID: 16446457</ref><ref name = "Fujii2007"/> in vegetative tissue and stress tolerance and growth regulation.		The core ABA signaling pathway is shown in the figure to the left. In unstimulated cells, the ABA receptor (R) is an unliganded dimer<ref>PMID:19898420</ref><ref>PMID:19933100</ref><ref>PMID:23265948</ref><ref>"PMID:22579247</ref> (monomer shown) in the cytosol and nucleus, and the SNRK2 protein kinase (K) is bound to a protein phosphatase 2C (P) in a complex (K-P) in which the kinase is dephosphorylated and inactivated by the phosphatase. When the ABA level rises, ABA binds to the ABA receptor<ref>PMID:19893533</ref><ref>PMID:19407143</ref><ref>PMID:19407142</ref>, and this creates a binding surface for PP2C. The activated receptor (R<sup>.</sup>ABA) dissociates to monomers which bind to protein phosphatase 2C<ref>PMID:19624469</ref> (R<sup>.</sup>ABA-P). The sequestration of the protein phosphatase frees the protein kinase to be activated by autophosphorylation or phosphorylation by another protein kinase. Activation of SnRK2.6/OST1/SRK2E leads to phosphorylation of: 1) ion channels SLAC1<ref>PMID: 19955405</ref> and KAT1<ref>PMID:19785574</ref> in guard cells and stomatal closure; 2) transcription factor ABI5<ref name = "Nakashima2009"/> in seeds/seedlings and dormancy/growth arrest; or 3) phosphorylation of transcription factor AREB/ABF <ref>PMID: 16446457</ref><ref name = "Fujii2007"/> in vegetative tissue and stress tolerance and growth regulation.

	Structures in the figure are: R, apo PYL2, [[3kdh]]; R<sup>.</sup>ABA, PYL2<sup>.</sup>ABA, [[3kdi]]; K-P; SnRK2.6-HAB1, [[3ujg]]; R<sup>.</sup>ABA-P, PYL2<sup>.</sup>ABA-ABI2, [[3ujl]]; K, SnRK2.6,[[3uc4]].		Structures in the figure are: R, apo PYL2, [[3kdh]]; R<sup>.</sup>ABA, PYL2<sup>.</sup>ABA, [[3kdi]]; K-P; SnRK2.6-HAB1, [[3ujg]]; R<sup>.</sup>ABA-P, PYL2<sup>.</sup>ABA-ABI2, [[3ujl]]; K, SnRK2.6,[[3uc4]].

Alice Harmon: New page: left Abscisic acid (ABA,) Abscisic Acid is a plant hormone that regulates seed development, dormancy and germination, s...

2013-10-05T16:34:19Z

New page: left Abscisic acid (ABA,)thumb| Abscisic Acid is a plant hormone that regulates seed development, dormancy and germination, s...

New page

[[Image:ABA model 2 med.jpg|left]]

Abscisic acid (ABA,)[[Image:Abscisic acid.svg.png|thumb| Abscisic Acid]] is a plant hormone that regulates seed development, dormancy and germination, stomatal closure, and responses to drought stress, and its core signaling pathway has recently been identified.<ref>PMID:15012233</ref><ref>PMID:12045268</ref><ref>PMID:20192755</ref> In Arabidopsis, this pathway involves families of ABA receptors (PYR1/RCAR11, PYL1/RCAR12, PYL2/RCAR14, PYL3/RCAR13, PYL8/RCAR3, PYL9/RCAR1)<ref>PMID:19407143</ref><ref>PMID:19407142</ref><ref>"PMID:22579247</ref><ref>PMID:23370718</ref>, protein phosphatase 2Cs (ABI1, ABI2, HAB1, HAB2, PP2CA/AHG3)<ref>PMID:19407143</ref><ref>PMID:19407142</ref><ref>PMID:16339800</ref>, SNRK2 protein kinases ([[SnRK2.6/OST1/SRK2E]], SNRK2.2/SRK2D and SnRK2.3/SRK2IA).<ref name = "Mustilli2002">PMID:12468729</ref><ref>PMID:12514244</ref><ref name = "Nakashima2009">PMID:19541597</ref><ref name = "Fujii2007">PMID:17307925</ref>

The core ABA signaling pathway is shown in the figure to the left. In unstimulated cells, the ABA receptor (R) is an unliganded dimer<ref>PMID:19898420</ref><ref>PMID:19933100</ref><ref>PMID:23265948</ref><ref>"PMID:22579247</ref> (monomer shown) in the cytosol and nucleus, and the SNRK2 protein kinase (K) is bound to a protein phosphatase 2C (P) in a complex (K-P) in which the kinase is dephosphorylated and inactivated by the phosphatase. When the ABA level rises ABA binds to the ABA receptor<ref>PMID:19893533</ref><ref>PMID:19407143</ref><ref>PMID:19407142</ref>, and this creates a binding surface for PP2C. The activated receptor (R.ABA) dissociates to monomers which bind to protein phosphatase 2C<ref>PMID:19624469</ref> (R.ABA-P). The sequestration of the protein phosphatase frees the protein kinase to be activated by autophosphorylation or phosphorylation by another protein kinase. Activation of SnRK2.6/OST1/SRK2E leads to phosphorylation of: 1) ion channels SLAC1<ref>PMID: 19955405</ref> and KAT1<ref>PMID:19785574</ref> in guard cells and stomatal closure; 2) transcription factor ABI5<ref name = "Nakashima2009"/> in seeds/seedlings and dormancy/growth arrest; or 3) phosphorylation of transcription factor AREB/ABF <ref>PMID: 16446457</ref><ref name = "Fujii2007"/> in vegetative tissue and stress tolerance and growth regulation.

Structures in the figure are: R, apo PYL2, [[3kdh]]; R.ABA, PYL2.ABA, [[3kdi]]; K-P; SnRK2.6-HAB1, [[3ujg]]; R.ABA-P, PYL2.ABA-ABI2, [[3ujl]]; K, SnRK2.6,[[3uc4]].

For further information about proteins involved in this pathway see [[PYR/PYL/RCAR family of ABA receptors]], [[ABA-regulated Protein Phosphatase 2C]], [[ABA-regulated SNRK2 Protein Kinase]].

==References==

<references/>

==See Also==
[http://en.wikipedia.org/wiki/Abscisic_acid] Abscisic Acid in Wikipedia