User:Alice Harmon/Sandbox 5

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Pyr/Pyl/RCAR family of ABA receptorsPyr/Pyl/RCAR family of ABA receptors

ABA signaling pathwayABA signaling pathway

Abscisic acid (ABA,)

Abscisic Acid

is a plant hormone that regulates seed dormancy and germination, stomatal closure, and responses to drought stress. As shown in the left figure, ABA binds to an ABA receptor (R)[1][2][3]. The activated receptor (R.ABA) binds to a protein phosphatase 2C (R.ABA-P), which was formerly in a complex with a SnRK2 protein kinase. The protein kinase is now free 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[4] and KAT1[5] in guard cells and stomatal closure; 2) transcription factor ABI5[6] in seeds/seedlings and dormancy/growth arrest; or 3) phosphorylation of transcription factor AREB/ABF [7][8] in vegetative tissue and stress tolerance and growth regulation.

The ABA receptor family includes PYR1, PYR2, PYL1, PYL2, and RCAR. The ABA-responsive protein phosphatase 2Cs are in Clade C and they include ABI1, ABI2, and HAB1. The ABA-activated protein kinases are in subclass III of SnRK2s and they include SnRK2.6/OST1/SRK2E, and SNRK2.2/SRK2D and SnRK2.3/SRK2I

Structures in the figure are: R, apo PYR2, 3kdh; R.ABA, PYR2.ABA, 3kdi; K-P; SnRK2.6-HAB1, 3ujg; R.ABA-P, PYR2.ABA-ABI2, 3ujl; K, SnRK2.6,3uc4.

The following Proteopedia pages



ReferencesReferences

  1. ↑ Yin P, Fan H, Hao Q, Yuan X, Wu D, Pang Y, Yan C, Li W, Wang J, Yan N. Structural insights into the mechanism of abscisic acid signaling by PYL proteins. Nat Struct Mol Biol. 2009 Dec;16(12):1230-6. Epub 2009 Nov 5. PMID:19893533 doi:10.1038/nsmb.1730
  2. ↑ Ma Y, Szostkiewicz I, Korte A, Moes D, Yang Y, Christmann A, Grill E. Regulators of PP2C phosphatase activity function as abscisic acid sensors. Science. 2009 May 22;324(5930):1064-8. doi: 10.1126/science.1172408. Epub 2009, Apr 30. PMID:19407143 doi:10.1126/science.1172408
  3. ↑ Park SY, Fung P, Nishimura N, Jensen DR, Fujii H, Zhao Y, Lumba S, Santiago J, Rodrigues A, Chow TF, Alfred SE, Bonetta D, Finkelstein R, Provart NJ, Desveaux D, Rodriguez PL, McCourt P, Zhu JK, Schroeder JI, Volkman BF, Cutler SR. Abscisic acid inhibits type 2C protein phosphatases via the PYR/PYL family of START proteins. Science. 2009 May 22;324(5930):1068-71. doi: 10.1126/science.1173041. Epub 2009, Apr 30. PMID:19407142 doi:10.1126/science.1173041
  4. ↑ Geiger D, Scherzer S, Mumm P, Stange A, Marten I, Bauer H, Ache P, Matschi S, Liese A, Al-Rasheid KA, Romeis T, Hedrich R. Activity of guard cell anion channel SLAC1 is controlled by drought-stress signaling kinase-phosphatase pair. Proc Natl Acad Sci U S A. 2009 Dec 15;106(50):21425-30. doi:, 10.1073/pnas.0912021106. Epub 2009 Dec 2. PMID:19955405 doi:10.1073/pnas.0912021106
  5. ↑ Sato A, Sato Y, Fukao Y, Fujiwara M, Umezawa T, Shinozaki K, Hibi T, Taniguchi M, Miyake H, Goto DB, Uozumi N. Threonine at position 306 of the KAT1 potassium channel is essential for channel activity and is a target site for ABA-activated SnRK2/OST1/SnRK2.6 protein kinase. Biochem J. 2009 Dec 10;424(3):439-48. doi: 10.1042/BJ20091221. PMID:19785574 doi:10.1042/BJ20091221
  6. ↑ Nakashima K, Fujita Y, Kanamori N, Katagiri T, Umezawa T, Kidokoro S, Maruyama K, Yoshida T, Ishiyama K, Kobayashi M, Shinozaki K, Yamaguchi-Shinozaki K. Three Arabidopsis SnRK2 protein kinases, SRK2D/SnRK2.2, SRK2E/SnRK2.6/OST1 and SRK2I/SnRK2.3, involved in ABA signaling are essential for the control of seed development and dormancy. Plant Cell Physiol. 2009 Jul;50(7):1345-63. doi: 10.1093/pcp/pcp083. Epub 2009, Jun 18. PMID:19541597 doi:10.1093/pcp/pcp083
  7. ↑ Furihata T, Maruyama K, Fujita Y, Umezawa T, Yoshida R, Shinozaki K, Yamaguchi-Shinozaki K. Abscisic acid-dependent multisite phosphorylation regulates the activity of a transcription activator AREB1. Proc Natl Acad Sci U S A. 2006 Feb 7;103(6):1988-93. Epub 2006 Jan 30. PMID:16446457 doi:10.1073/pnas.0505667103
  8. ↑ Fujii H, Verslues PE, Zhu JK. Identification of two protein kinases required for abscisic acid regulation of seed germination, root growth, and gene expression in Arabidopsis. Plant Cell. 2007 Feb;19(2):485-94. Epub 2007 Feb 16. PMID:17307925 doi:tpc.106.048538

See AlsoSee Also

[1] Abscisic Acid in Wikipedia

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