| 词条 | Cytokinin signaling and response regulator protein |
| 释义 |
A cytokinin signaling and response regulator protein is a plant protein that is involved in a two step cytokinin signaling and response regulation pathway. The current model of cytokinin signaling and response regulation shows that it works as a multi-step phosphorelay two-component signaling system.[1] This type of system is similar to two-component signaling systems in bacteria.[1] The cytokinin signaling pathway consists of sensor kinases, histidine phosphotransfer proteins, and response regulators.[1] In this system, cytokinin sensor kinases are activated by the presence of cytokinins.[1] The sensor kinase then autophosphorylates, transferring a phosphate from its kinase domain to its receiver domain.[1] The phosphate is then transferred to a histidine phosphotransfer protein which then phosphorylates a response regulator.[1] The response regulators can then serve as positive or negative regulators of the signaling mechanism and affect gene expression within the plant cells.[1] This system is a called a two-step system because it involves two steps to transfer the phosphate to the final target, the response regulators.[1] Cytokinin cause a rapid increase in the expression ofresponse regulator genes Cytokinins are a class of phytohormones that promote cell division in plants.[2] Cytokinins participate in short and long-distance signaling and are transported for this signaling through the xylem of plants.[2] Cytokinins control the differentiation of meristem cells in plant development, particularly in shoots and roots where plants undergo growth.[3] Cytokinins act in a restricted region of the root meristem, and their signaling and regulation of genes occurs through a multi-step phosphorelay mediate by cytokinin histidine sensor kinases, histidine phosphotransfer proteins, and cytokinin response regulator proteins.[4] Cytokinin sensor kinasesCytokinin sensor kinases are the initial sensors that detect and are bound by cytokinins.[1] Research with maize and Arabidopsis thaliana suggest that some cytokinin sensor kinases bind multiple types of cytokinins while other cytokinin sensor kinases are specific for distinct cytokinins.[1] AHK4, a cytokinin histidine kinase in Arabidopsis thaliana, is a cytokinin sensor that allows binding of multiple types of cytokinins.[1] AHK4 has been shown, through three-dimensional modeling, to completely surround bound cytokinin in the binding pocket.[1] AHK2 and AHK3 have been shown to be critically involved in drought tolerance.[5] These receptors activate dehydration tolerance response within one hour of dehydration and continue activation through eight hours.[5] Histidine phosphotransfer proteinsHistidine phosphotransfer proteins transfer the phosphate in the multistep phosphorelay signaling pathway from cytokinin sensor kinases to their final target, cytokinin response regulators.[6] In Arabidopsis thaliana, most histidine phosphotransfer proteins are redundant, positive regulators in cytokinin signaling.[6] Most of the Arabidopsis thaliana histidine phosphotransfer proteins have functional overlap and affect many aspects of plant development.[6] AHP4, however, might play a negative role in cytokinin responses.[6] Cytokinin response regulatorsCytokinin response regulators proteins are the final target of the two-step phosphorelay.[4] These response regulators fall into three known classes: type A response regulators, type B response regulators, and type C response regulators.[7] Type AType A cytokinin response regulators serve as negative regulators for cytokinin signaling.[4] Cytokinin causes the rapid induction of type A response regulators.[4] The type A cytokinin response regulator family in Arabidopsis thaliana consists of 10 genes.[8] Expression of type A cytokinin response regulators decreases sensitivity to cytokinins, and a lack of type-A cytokinin response regulators leads to increased sensitivity to cytokinins.[9] Type A cytokinin response regulators can act as negative regulators of cytokinin signaling by either competing with type-B positive regulators or by regulating the pathway through direct and indirect interactions with other pathway mechanisms.[4] Type A cytokinin response regulators are also likely involved in light signal transduction.[8] ARR3 and ARR4 are involved in the synchronization of the circadian clock of Arabidopsis thaliana with external time and photoperiod.[9] Type BType B cytokinin response regulators are the positive regulators that oppose the negative regulation of type A cytokinin response regulators in the two-component cytokinin signaling pathway.[32] These regulators play a critical role in early response to cytokinin.[10] Differing expression of type-B cytokinin response regulators likely play a role in controlling cellular response to cytokinins.[11] The type-B cytokinin response regulator family consists of two subfamilies and one major subfamily.[11] The major family of type-B cytokinin response regulators are expressed in locations on the plant that are heavily influenced by cytokinins.[11] These regions where type-B cytokinin response regulators are heavily expressed include apical meristem regions and budding leaves.[11] ARR1, ARR10, and ARR12 have been indicated to mediate root growth response.[10] Each of ARR1, ARR10, and ARR12 vary in their effect on root growth response, likely related to differences in root expression patterns.[10] ARR1, ARR10, and ARR12 have been determined to have a functional overlap with type B response regulators.[10] Type CType-C cytokinin response regulators are unique in that their expression is not induced by cytokinins like type-A cytokinin response regulators and type-B cytokinin response regulators.[12] ARR22 and ARR22 and ARR24 are the two known type-C cytokinin response regulators in Arabidopsis thaliana.[12] Research suggests that ARR22 plays a positive role in stress tolerance by improving cell membrane integrity.[12] Increases in expression of ARR22 modulates abiotic stress-responsive genes, possibly aiding in drought and freezing tolerance.[12] However, the role of ARR24 in Arabidopsis plant signaling remains undetermined.[12] References1. ^1 2 3 4 5 6 7 8 9 10 {{cite journal | vauthors = Ferreira FJ, Kieber JJ | title = Cytokinin signaling | journal = Current Opinion in Plant Biology | volume = 8 | issue = 5 | pages = 518–25 | date = October 2005 | pmid = 16054432 | doi = 10.1016/j.pbi.2005.07.013 }} 2. ^1 {{cite journal | vauthors = Sakakibara H | title = Cytokinins: activity, biosynthesis, and translocation | journal = Annual Review of Plant Biology | volume = 57 | pages = 431–49 | date = 2006 | pmid = 16669769 | doi = 10.1146/annurev.arplant.57.032905.105231 }} 3. ^{{cite journal | vauthors = Dello Ioio R, Linhares FS, Scacchi E, Casamitjana-Martinez E, Heidstra R, Costantino P, Sabatini S | title = Cytokinins determine Arabidopsis root-meristem size by controlling cell differentiation | journal = Current Biology | volume = 17 | issue = 8 | pages = 678–82 | date = April 2007 | pmid = 17363254 | doi = 10.1016/j.cub.2007.02.047 }} 4. ^1 2 3 4 {{cite journal | vauthors = To JP, Deruère J, Maxwell BB, Morris VF, Hutchison CE, Ferreira FJ, Schaller GE, Kieber JJ | title = Cytokinin regulates type-A Arabidopsis Response Regulator activity and protein stability via two-component phosphorelay | journal = The Plant Cell | volume = 19 | issue = 12 | pages = 3901–14 | date = December 2007 | pmid = 18065689 | pmc = 2217641 | doi = 10.1105/tpc.107.052662 }} 5. ^1 {{cite journal | vauthors = Kang NY, Cho C, Kim NY, Kim J | title = Cytokinin receptor-dependent and receptor-independent pathways in the dehydration response of Arabidopsis thaliana | journal = Journal of Plant Physiology | volume = 169 | issue = 14 | pages = 1382–91 | date = September 2012 | pmid = 22704545 | doi = 10.1016/j.jplph.2012.05.007 }} 6. ^1 2 3 {{cite journal | vauthors = Hutchison CE, Li J, Argueso C, Gonzalez M, Lee E, Lewis MW, Maxwell BB, Perdue TD, Schaller GE, Alonso JM, Ecker JR, Kieber JJ | title = The Arabidopsis histidine phosphotransfer proteins are redundant positive regulators of cytokinin signaling | journal = The Plant Cell | volume = 18 | issue = 11 | pages = 3073–87 | date = November 2006 | pmid = 17122069 | pmc = 1693944 | doi = 10.1105/tpc.106.045674 }} 7. ^{{cite journal | vauthors = Schaller GE, Doi K, Hwang I, Kieber JJ, Khurana JP, Kurata N, Mizuno T, Pareek A, Shiu SH, Wu P, Yip WK | title = Nomenclature for two-component signaling elements of rice | journal = Plant Physiology | volume = 143 | issue = 2 | pages = 555–7 | date = February 2007 | pmid = 17284581 | pmc = 1803756 | doi = 10.1104/pp.106.093666 }} 8. ^1 {{cite journal | vauthors = To JP, Haberer G, Ferreira FJ, Deruère J, Mason MG, Schaller GE, Alonso JM, Ecker JR, Kieber JJ | title = Type-A Arabidopsis response regulators are partially redundant negative regulators of cytokinin signaling | language = en | journal = The Plant Cell | volume = 16 | issue = 3 | pages = 658–71 | date = March 2004 | pmid = 14973166 | doi = 10.1105/tpc.018978 | pmc = 385279 }} 9. ^1 {{cite journal | vauthors = Salomé PA, To JP, Kieber JJ, McClung CR | title = Arabidopsis response regulators ARR3 and ARR4 play cytokinin-independent roles in the control of circadian period | journal = The Plant Cell | volume = 18 | issue = 1 | pages = 55–69 | date = January 2006 | pmid = 16326927 | pmc = 1323484 | doi = 10.1105/tpc.105.037994 }} 10. ^1 2 3 4 {{cite journal | vauthors = Argyros RD, Mathews DE, Chiang YH, Palmer CM, Thibault DM, Etheridge N, Argyros DA, Mason MG, Kieber JJ, Schaller GE | title = Type B response regulators of Arabidopsis play key roles in cytokinin signaling and plant development | journal = The Plant Cell | volume = 20 | issue = 8 | pages = 2102–16 | date = August 2008 | pmid = 18723577 | pmc = 2553617 | doi = 10.1105/tpc.108.059584 }} 11. ^1 2 3 {{cite journal | vauthors = Mason MG, Li J, Mathews DE, Kieber JJ, Schaller GE | title = Type-B response regulators display overlapping expression patterns in Arabidopsis | journal = Plant Physiology | volume = 135 | issue = 2 | pages = 927–37 | date = June 2004 | pmid = 15173562 | doi = 10.1104/pp.103.038109 | pmc = 514127 }} 12. ^1 2 3 4 5 {{cite journal | vauthors = Kang NY, Cho C, Kim J | title = Inducible expression of Arabidopsis response regulator 22 (ARR22), a type-C ARR, in transgenic Arabidopsis enhances drought and freezing tolerance | journal = PLoS One | volume = 8 | issue = 11 | pages = e79248 | date = November 2013 | pmid = 24244460 | pmc = 3828410 | doi = 10.1371/journal.pone.0079248 }} 2 : Plant proteins|Cytokinins |
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