3t4o

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]}

References

1. ↑ Mahonen AP, Bonke M, Kauppinen L, Riikonen M, Benfey PN, Helariutta Y. A novel two-component hybrid molecule regulates vascular morphogenesis of the Arabidopsis root. Genes Dev. 2000 Dec 1;14(23):2938-43. PMID:11114883
2. ↑ Inoue T, Higuchi M, Hashimoto Y, Seki M, Kobayashi M, Kato T, Tabata S, Shinozaki K, Kakimoto T. Identification of CRE1 as a cytokinin receptor from Arabidopsis. Nature. 2001 Feb 22;409(6823):1060-3. PMID:11234017 doi:http://dx.doi.org/10.1038/35059117
3. ↑ Suzuki T, Miwa K, Ishikawa K, Yamada H, Aiba H, Mizuno T. The Arabidopsis sensor His-kinase, AHk4, can respond to cytokinins. Plant Cell Physiol. 2001 Feb;42(2):107-13. PMID:11230563
4. ↑ Ueguchi C, Sato S, Kato T, Tabata S. The AHK4 gene involved in the cytokinin-signaling pathway as a direct receptor molecule in Arabidopsis thaliana. Plant Cell Physiol. 2001 Jul;42(7):751-5. PMID:11479382
5. ↑ Yamada H, Suzuki T, Terada K, Takei K, Ishikawa K, Miwa K, Yamashino T, Mizuno T. The Arabidopsis AHK4 histidine kinase is a cytokinin-binding receptor that transduces cytokinin signals across the membrane. Plant Cell Physiol. 2001 Sep;42(9):1017-23. PMID:11577198
6. ↑ 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
7. ↑ 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
8. ↑ Nishimura C, Ohashi Y, Sato S, Kato T, Tabata S, Ueguchi C. Histidine kinase homologs that act as cytokinin receptors possess overlapping functions in the regulation of shoot and root growth in Arabidopsis. Plant Cell. 2004 Jun;16(6):1365-77. Epub 2004 May 21. PMID:15155880 doi:http://dx.doi.org/10.1105/tpc.021477
9. ↑ Spichal L, Rakova NY, Riefler M, Mizuno T, Romanov GA, Strnad M, Schmulling T. Two cytokinin receptors of Arabidopsis thaliana, CRE1/AHK4 and AHK3, differ in their ligand specificity in a bacterial assay. Plant Cell Physiol. 2004 Sep;45(9):1299-305. PMID:15509853 doi:http://dx.doi.org/10.1093/pcp/pch132
10. ↑ de Leon BG, Zorrilla JM, Rubio V, Dahiya P, Paz-Ares J, Leyva A. Interallelic complementation at the Arabidopsis CRE1 locus uncovers independent pathways for the proliferation of vascular initials and canonical cytokinin signalling. Plant J. 2004 Apr;38(1):70-9. PMID:15053761 doi:http://dx.doi.org/10.1111/j.1365-313X.2004.02023.x
11. ↑ Maruyama-Nakashita A, Nakamura Y, Yamaya T, Takahashi H. A novel regulatory pathway of sulfate uptake in Arabidopsis roots: implication of CRE1/WOL/AHK4-mediated cytokinin-dependent regulation. Plant J. 2004 Jun;38(5):779-89. PMID:15144379 doi:http://dx.doi.org/10.1111/j.1365-313X.2004.02079.x
12. ↑ 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:http://dx.doi.org/10.1073/pnas.0402887101
13. ↑ 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:http://dx.doi.org/10.1016/j.ab.2005.09.012
14. ↑ 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:http://dx.doi.org/10.1104/pp.105.060517
15. ↑ 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:http://dx.doi.org/10.1104/pp.104.057174
16. ↑ 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:http://dx.doi.org/10.1016/j.cub.2006.04.030
17. ↑ 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:http://dx.doi.org/10.1093/jxb/erl179
18. ↑ 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:http://dx.doi.org/10.1105/tpc.105.037796
19. ↑ 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:http://dx.doi.org/10.1093/pcp/pci240
20. ↑ 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:http://dx.doi.org/10.1007/s00425-006-0464-0
21. ↑ 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:http://dx.doi.org/10.1093/pcp/pcm145
22. ↑ 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:http://dx.doi.org/10.1073/pnas.0706547105
23. ↑ Lopez-Bucio J, Millan-Godinez M, Mendez-Bravo A, Morquecho-Contreras A, Ramirez-Chavez E, Molina-Torres J, Perez-Torres A, Higuchi M, Kakimoto T, Herrera-Estrella L. Cytokinin receptors are involved in alkamide regulation of root and shoot development in Arabidopsis. Plant Physiol. 2007 Dec;145(4):1703-13. Epub 2007 Oct 26. PMID:17965178 doi:http://dx.doi.org/10.1104/pp.107.107953
24. ↑ Kopecny D, Sebela M, Briozzo P, Spichal L, Houba-Herin N, Masek V, Joly N, Madzak C, Anzenbacher P, Laloue M. Mechanism-based inhibitors of cytokinin oxidase/dehydrogenase attack FAD cofactor. J Mol Biol. 2008 Jul 25;380(5):886-99. Epub 2008 May 24. PMID:18571199 doi:10.1016/j.jmb.2008.05.044
25. ↑ 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:http://dx.doi.org/10.1094/MPMI-21-10-1371
26. ↑ 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:http://dx.doi.org/10.1111/j.1365-313X.2008.03502.x
27. ↑ 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:http://dx.doi.org/10.1111/j.1742-4658.2008.06777.x
28. ↑ 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:http://dx.doi.org/10.1242/dev.041426