title: Cytokinin inhibition of leaf senescence.
abstract: The senescence delaying effect of cytokinin is well known, however, the details behind how this process occurs remain unclear. Efforts to improve understanding of this phenomenon have led to the identification in Arabidopsis of specific cytokinin signaling components through which senescence signal responses are regulated. These include the cytokinin receptor (AHK3), the type-B response regulator (ARR2) and the recently identified cytokinin response factor (CRF6). At the mechanistic end of this process, it was found that increased cell-wall invertase activity which occurs in response to cytokinin is both necessary and sufficient for the inhibition of senescence. Yet, a direct link between the signaling and mechanistic steps of a cytokinin regulated senescence process has yet to be demonstrated. This may be in part because the relationship between senescence and primary metabolism implied by the key role of cell-wall invertase is the subject of two apparently opposing bodies of evidence. Here we briefly summarize and propose a model in which cytokinin mediated changes in sink/source relationships leads to delayed senescence which is consistent with existing evidence both for and against sugars as a trigger for developmental senescence.
authors: Department of Biological Sciences; Auburn University; Auburn, AL USA.
authors: Paul J
authors: PJ
authors: Zwack
authors: Aaron M
authors: AM
authors: Rashotte
mesh_terms: D003583:Cytokinins / Q000502:physiology*; D018515:Plant Leaves / Q000502:physiology*
chemical_list: D003583:Cytokinins
keywords: carbon allocation; cell wall invertase; cytokinin; leaf; senescence; sink/source relationships
references: Plant Cell. 2004 May;16(5):1276-87
references: 15100396
references: Plant Mol Biol. 1996 Feb;30(4):739-54
references: 8624406
references: Plant Mol Biol. 2000 Nov;44(4):451-61
references: 11197321
references: Plant Physiol. 1990 May;93(1):33-9
references: 16667455
references: Plant Cell. 1990 Oct;2(10):1027-38
references: 2136626
references: J Exp Bot. 2008;59(8):1963-72
references: 18453532
references: Plant Cell Rep. 2012 May;31(5):801-12
references: 22315145
references: Proc Natl Acad Sci U S A. 2006 Jul 18;103(29):11081-5
references: 16832061
references: Plant Cell. 2009 Jul;21(7):2072-89
references: 19574437
references: Plant Cell Physiol. 2013 Jun;54(6):971-81
references: 23539244
references: Physiol Plant. 2001 Mar;111(3):345-352
references: 11240919
references: Plant Cell Physiol. 2012 Oct;53(10):1683-95
references: 22864451
references: Physiol Plant. 2004 Feb;120(2):338-346
references: 15032869
references: J Integr Plant Biol. 2010 Jul;52(7):653-69
references: 20590995
references: Plant J. 2010 Mar;61(6):1067-91
references: 20409279
references: Proc Natl Acad Sci U S A. 1988 Jul;85(14):5131-5
references: 16593957
references: Plant Cell. 2011 Mar;23(3):873-94
references: 21447789
references: Plant J. 2005 May;42(4):567-85
references: 15860015
references: J Exp Bot. 2006;57(2):391-9
references: 16157653
references: Planta. 1991 Aug;185(1):81-90
references: 24186283
references: Proc Natl Acad Sci U S A. 2006 Jan 17;103(3):814-9
references: 16407152
references: Planta. 2005 Dec;222(6):989-1000
references: 16034594
references: Plant Sci. 2011 Sep;181(3):288-99
references: 21763540
references: Science. 1995 Dec 22;270(5244):1986-8
references: 8592746
references: Plant J. 1997 Mar;11(3):539-48
references: 9107040
references: J Exp Bot. 2008;59(2):377-87
references: 18267946
references: Plant Cell Rep. 2007 May;26(5):611-5
references: 17149639
references: Plant Cell. 1993 May;5(5):553-64
references: 8518555
references: Plant Physiol. 1989 Oct;91(2):656-62
references: 16667083
references: J Exp Bot. 2011 Oct;62(14):4995-5002
references: 21705390
references: Science. 2012 Jan 13;335(6065):207-11
references: 22157085
references: Plant Biol (Stuttg). 2006 Sep;8(5):579-86
references: 16883480
references: Plant Physiol. 2011 Jan;155(1):64-9
references: 20971857
references: Plant J. 2012 Mar;69(6):934-45
references: 22050482
references: Annu Rev Plant Biol. 2009;60:207-21
references: 19025382
references: Planta. 1991 Dec;183(1):40-50
references: 24193531
references: Plant Physiol. 2001 Oct;127(2):505-16
references: 11598225
references: New Phytol. 2013 Feb;197(3):696-711
references: 23176101
references: Dev Biol. 1992 Oct;153(2):386-95
references: 1397692
references: Science. 2003 Apr 11;300(5617):332-6
references: 12690200
references: Plant Cell Physiol. 2004 Jan;45(1):28-39
references: 14749483
references: Plant Biol (Stuttg). 2010 Jan;12(1):60-9
references: 20653888
references: Plant Physiol. 1977 Mar;59(3):448-54
references: 16659871
references: Plant Physiol. 2004 Jun;135(2):927-37
references: 15173562
references: Plant Cell Rep. 2004 Jun;22(11):816-21
references: 14963691
references: J Exp Bot. 2012 May;63(9):3499-509
references: 22641615
references: Plant Cell Rep. 2012 May;31(5):789-99
references: 22350315
references: Plant Physiol. 1997 Sep;115(1):273-82
references: 9306701
references: Proc Natl Acad Sci U S A. 2004 Jun 8;101(23):8821-6
references: 15166290
references: Proc Natl Acad Sci U S A. 1984 Oct;81(19):5994-8
references: 6091129
references: J Exp Bot. 2002 Apr;53(370):927-37
references: 11912235
references: Plant Cell Physiol. 2008 Jan;49(1):47-57
references: 18037673
references: J Exp Bot. 2003 Jan;54(382):539-47
references: 12508065