| Structural highlights
Function
AHK4_ARATH Cytokinins (CK) receptor related to bacterial two-component regulators. Functions as a histidine kinase and transmits the stress signal to a downstream MAPK cascade. This protein undergoes an ATP-dependent autophosphorylation at a conserved histidine residue in the kinase core, and a phosphoryl group is then transferred to a conserved aspartate residue in the receiver domain. In the presence of cytokinin, feed phosphate to phosphorelay-integrating histidine phosphotransfer protein (HPt) and activates subsequent cascade. In the absence of cytokinin, removes phosphate from HPt proteins, decreasing the system phosphoload. Involved in meristems establishment in seedlings. Acts as a redundant negative regulator of drought and salt stress responses, and abscisic acid (ABA) signaling in a cytokinin-dependent manner. Required to set vascular asymmetric cell divisions that establish phloem and procambium cell lines. Redundant positive regulator of cytokinin signaling that regulates many development process including seed germination, cell division, seed size, chlorophyll retention during leaf senescence, root repression and shoot promotion. Can interact with isoprenoid-type cytokinins trans-zeatin (tZ and tZR), isopentenyladenine (iP), and isopentenyladenosine (iPR), the meta hydroxylated derivative of benzyladenine m-topolin, buta-2,3-dienyladenine (HA-8), penta-2,3-dienyladenine (HA-1), 4-methyl-penta-2,3-dienyladenine (HA-10), 4-hydroxy-2-butynyladenine (RM1), 2-butynyladenine (RM6), and to a lower extent, with cis-zeatin (cZ), zeatin riboside and dihydrozeatin (DZ). Together with AHK3, involved in the cytokinin-dependent responses to Pi starvation and sucrose stresses. Required for the formation of auxin-transporting vascular tissues in the hypocotyl, and primary and lateral roots, but not in adventitious roots, thus leading to auxin basipetal transport that regulates root development and branching. Involved in alkamides (e.g. N-isobutyl decanamide) and N-acylethanolamides (NAE) signaling that control meristematic activity and differentiation processes during plant development. Prevents the uptake of sulfate by mediating cytokinin-dependent down-regulation of high-affinity sulfate transporters (e.g. SULTR1;1 and SULTR1;2) expression in roots. Together with AHK2, required for growth and reproduction promotion stimulated by the endophytic fungus Piriformospora indica in a trans-zeatin-dependent manner. Required to trigger the phytotoxic effect of the snapdragon (Antirrhinum majus) flowers volatile organic compound (VOC) methyl benzoate (MB). Plays a role in the cytokinin-mediated repression of the iron uptake pathway.[1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21] [22] [23] [24] [25] [26] [27] [28]
Publication Abstract from PubMed
Cytokinins are classic hormones that orchestrate plant growth and development and the integrity of stem cell populations. Cytokinin receptors are eukaryotic sensor histidine kinases that are activated by both naturally occurring adenine-type cytokinins and urea-based synthetic compounds. Crystal structures of the Arabidopsis thaliana histidine kinase 4 sensor domain in complex with different cytokinin ligands now rationalize the hormone-binding specificity of the receptor and may spur the design of new cytokinin ligands.
Structural basis for cytokinin recognition by Arabidopsis thaliana histidine kinase 4.,Hothorn M, Dabi T, Chory J Nat Chem Biol. 2011 Oct 2;7(11):766-8. doi: 10.1038/nchembio.667. PMID:21964459[29]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
References
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- ↑ Kiba T, Yamada H, Mizuno T. Characterization of the ARR15 and ARR16 response regulators with special reference to the cytokinin signaling pathway mediated by the AHK4 histidine kinase in roots of Arabidopsis thaliana. Plant Cell Physiol. 2002 Sep;43(9):1059-66. PMID:12354925
- ↑ Franco-Zorrilla JM, Martin AC, Solano R, Rubio V, Leyva A, Paz-Ares J. Mutations at CRE1 impair cytokinin-induced repression of phosphate starvation responses in Arabidopsis. Plant J. 2002 Nov;32(3):353-60. PMID:12410813
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- ↑ Higuchi M, Pischke MS, Mahonen AP, Miyawaki K, Hashimoto Y, Seki M, Kobayashi M, Shinozaki K, Kato T, Tabata S, Helariutta Y, Sussman MR, Kakimoto T. In planta functions of the Arabidopsis cytokinin receptor family. Proc Natl Acad Sci U S A. 2004 Jun 8;101(23):8821-6. Epub 2004 May 27. PMID:15166290 doi:https://dx.doi.org/10.1073/pnas.0402887101
- ↑ Romanov GA, Spichal L, Lomin SN, Strnad M, Schmulling T. A live cell hormone-binding assay on transgenic bacteria expressing a eukaryotic receptor protein. Anal Biochem. 2005 Dec 1;347(1):129-34. Epub 2005 Sep 30. PMID:16246292 doi:https://dx.doi.org/10.1016/j.ab.2005.09.012
- ↑ Franco-Zorrilla JM, Martin AC, Leyva A, Paz-Ares J. Interaction between phosphate-starvation, sugar, and cytokinin signaling in Arabidopsis and the roles of cytokinin receptors CRE1/AHK4 and AHK3. Plant Physiol. 2005 Jun;138(2):847-57. Epub 2005 May 27. PMID:15923327 doi:https://dx.doi.org/10.1104/pp.105.060517
- ↑ Mok MC, Martin RC, Dobrev PI, Vankova R, Ho PS, Yonekura-Sakakibara K, Sakakibara H, Mok DW. Topolins and hydroxylated thidiazuron derivatives are substrates of cytokinin O-glucosyltransferase with position specificity related to receptor recognition. Plant Physiol. 2005 Mar;137(3):1057-66. Epub 2005 Feb 22. PMID:15728338 doi:https://dx.doi.org/10.1104/pp.104.057174
- ↑ Mahonen AP, Higuchi M, Tormakangas K, Miyawaki K, Pischke MS, Sussman MR, Helariutta Y, Kakimoto T. Cytokinins regulate a bidirectional phosphorelay network in Arabidopsis. Curr Biol. 2006 Jun 6;16(11):1116-22. PMID:16753566 doi:https://dx.doi.org/10.1016/j.cub.2006.04.030
- ↑ Romanov GA, Lomin SN, Schmulling T. Biochemical characteristics and ligand-binding properties of Arabidopsis cytokinin receptor AHK3 compared to CRE1/AHK4 as revealed by a direct binding assay. J Exp Bot. 2006;57(15):4051-8. Epub 2006 Oct 30. PMID:17075078 doi:https://dx.doi.org/10.1093/jxb/erl179
- ↑ Riefler M, Novak O, Strnad M, Schmulling T. Arabidopsis cytokinin receptor mutants reveal functions in shoot growth, leaf senescence, seed size, germination, root development, and cytokinin metabolism. Plant Cell. 2006 Jan;18(1):40-54. Epub 2005 Dec 16. PMID:16361392 doi:https://dx.doi.org/10.1105/tpc.105.037796
- ↑ Kuroha T, Ueguchi C, Sakakibara H, Satoh S. Cytokinin receptors are required for normal development of auxin-transporting vascular tissues in the hypocotyl but not in adventitious roots. Plant Cell Physiol. 2006 Feb;47(2):234-43. Epub 2005 Dec 15. PMID:16357038 doi:https://dx.doi.org/10.1093/pcp/pci240
- ↑ Horiuchi J, Badri DV, Kimball BA, Negre F, Dudareva N, Paschke MW, Vivanco JM. The floral volatile, methyl benzoate, from snapdragon (Antirrhinum majus) triggers phytotoxic effects in Arabidopsis thaliana. Planta. 2007 Jun;226(1):1-10. Epub 2007 Jan 11. PMID:17216481 doi:https://dx.doi.org/10.1007/s00425-006-0464-0
- ↑ Miwa K, Ishikawa K, Terada K, Yamada H, Suzuki T, Yamashino T, Mizuno T. Identification of amino acid substitutions that render the Arabidopsis cytokinin receptor histidine kinase AHK4 constitutively active. Plant Cell Physiol. 2007 Dec;48(12):1809-14. Epub 2007 Oct 23. PMID:17956858 doi:https://dx.doi.org/10.1093/pcp/pcm145
- ↑ Tran LS, Urao T, Qin F, Maruyama K, Kakimoto T, Shinozaki K, Yamaguchi-Shinozaki K. Functional analysis of AHK1/ATHK1 and cytokinin receptor histidine kinases in response to abscisic acid, drought, and salt stress in Arabidopsis. Proc Natl Acad Sci U S A. 2007 Dec 18;104(51):20623-8. Epub 2007 Dec 12. PMID:18077346 doi:https://dx.doi.org/10.1073/pnas.0706547105
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- ↑ Vadassery J, Ritter C, Venus Y, Camehl I, Varma A, Shahollari B, Novak O, Strnad M, Ludwig-Muller J, Oelmuller R. The role of auxins and cytokinins in the mutualistic interaction between Arabidopsis and Piriformospora indica. Mol Plant Microbe Interact. 2008 Oct;21(10):1371-83. doi:, 10.1094/MPMI-21-10-1371. PMID:18785832 doi:https://dx.doi.org/10.1094/MPMI-21-10-1371
- ↑ Seguela M, Briat JF, Vert G, Curie C. Cytokinins negatively regulate the root iron uptake machinery in Arabidopsis through a growth-dependent pathway. Plant J. 2008 Jul;55(2):289-300. doi: 10.1111/j.1365-313X.2008.03502.x. Epub 2008, Apr 4. PMID:18397377 doi:https://dx.doi.org/10.1111/j.1365-313X.2008.03502.x
- ↑ Spichal L, Werner T, Popa I, Riefler M, Schmulling T, Strnad M. The purine derivative PI-55 blocks cytokinin action via receptor inhibition. FEBS J. 2009 Jan;276(1):244-53. doi: 10.1111/j.1742-4658.2008.06777.x. Epub 2008 , Nov 20. PMID:19032596 doi:https://dx.doi.org/10.1111/j.1742-4658.2008.06777.x
- ↑ Skylar A, Hong F, Chory J, Weigel D, Wu X. STIMPY mediates cytokinin signaling during shoot meristem establishment in Arabidopsis seedlings. Development. 2010 Feb;137(4):541-9. doi: 10.1242/dev.041426. PMID:20110319 doi:https://dx.doi.org/10.1242/dev.041426
- ↑ Hothorn M, Dabi T, Chory J. Structural basis for cytokinin recognition by Arabidopsis thaliana histidine kinase 4. Nat Chem Biol. 2011 Oct 2;7(11):766-8. doi: 10.1038/nchembio.667. PMID:21964459 doi:10.1038/nchembio.667
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