Identical amino acid substitutions in the repression domain of auxin/indole-3-acetic acid proteins have contrasting effects on auxin signaling.
Auxin/indole-3-acetic acid (Aux/IAA) proteins function as repressors of auxin response gene expression when auxin concentrations in a cell are low. At elevated auxin concentrations, these repressors are destroyed via the ubiquitin-proteasome pathway, resulting in derepression/activation of auxin response genes. Most Aux/IAA repressors contain four conserved domains, with one of these being an active, portable repression domain (domain I) and a second being an auxin-dependent instability domain (domain II). Here, we have analyzed the effects of amino acid substitutions in the repression domain of selected Aux/IAA proteins. We show that stabilized versions of Aux/IAA proteins with amino acid substitutions in domain I display contrasting phenotypes when expressed in transformed Arabidopsis (Arabidopsis thaliana) plants. An alanine-for-leucine substitution in the LxLxL (where L is leucine and x is another amino acid) repression domain of IAA3, IAA6, or IAA19 confers enhanced auxin response gene expression and "high-auxin" phenotypes when expressed from the 35S or IAA19 promoter (as tested with IAA19) in transformed Arabidopsis plants. In marked contrast, a single alanine-for-leucine substitution in domain I of IAA12 or IAA17 confers repression of auxin response genes and "low-auxin" phenotypes. These results point to intrinsic differences in the repression domain(s) of IAA proteins and suggest that some IAA proteins have stronger or more complex repression domains than others.
Department of Biochemistry, University of Missouri, Columbia, Missouri 65211, USA.
Hanbing
H
Li
Shiv B
SB
Tiwari
Gretchen
G
Hagen
Tom J
TJ
Guilfoyle
D019943:Amino Acid Substitution / Q000235:genetics*; D017360:Arabidopsis / Q000235:genetics; D029681:Arabidopsis Proteins / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D007210:Indoleacetic Acids / Q000378:metabolism*; D008954:Models, Biological; D009154:Mutation / Q000235:genetics; D010641:Phenotype; D030821:Plants, Genetically Modified; D011401:Promoter Regions, Genetic / Q000235:genetics; D017434:Protein Structure, Tertiary; D012097:Repressor Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D014170:Transformation, Genetic; D019076:Transgenes / Q000235:genetics
D029681:Arabidopsis Proteins; D007210:Indoleacetic Acids; D012097:Repressor Proteins; C030737:indoleacetic acid
Plant Cell. 2004 Feb;16(2):379-93
14729917
Plant Cell. 2001 Oct;13(10):2349-60
11595806
Plant Mol Biol. 2002 Jun-Jul;49(3-4):387-400
12036262
Plant Cell. 2001 Dec;13(12):2809-22
11752389
Plant Cell. 2005 Jul;17(7):1979-93
15923351
Plant Physiol. 2010 Mar;152(3):1109-34
20097792
Plant Cell. 2006 Mar;18(3):699-714
16489122
Plant Physiol. 2004 Jul;135(3):1738-52
15247399
Mol Biol Rep. 2010 Dec;37(8):3991-4001
20232157
Science. 2008 Mar 7;319(5868):1384-6
18258861
Annu Rev Cell Dev Biol. 2008;24:55-80
18631113
Plant Cell. 1997 Nov;9(11):1963-71
9401121
Plant Physiol. 2000 Jun;123(2):563-74
10859186
Plant J. 2006 Apr;46(2):297-306
16623891
J Mol Biol. 1995 Aug 25;251(4):533-49
7658471
Plant Physiol. 2009 Mar;149(3):1277-88
19129421
Plant Cell. 2001 Apr;13(4):829-41
11283339
Plant Cell. 2006 Nov;18(11):2958-70
17098810
Physiol Plant. 2008 Jun;133(2):397-405
18298415
Plant J. 1998 Dec;16(6):735-43
10069079
Plant Cell. 2003 Feb;15(2):533-43
12566590
Development. 2007 Feb;134(4):681-90
17215297
Science. 1998 Feb 27;279(5355):1371-3
9478901
Plant J. 2000 Mar;21(6):553-62
10758506
Proc Natl Acad Sci U S A. 1997 Oct 28;94(22):11786-91
9342315
Funct Integr Genomics. 2010 Nov;10(4):533-46
20499123
Nature. 2001 Nov 15;414(6861):271-6
11713520
Plant Physiol. 2009 Mar;149(3):1231-9
19168642
Plant Cell. 2004 Feb;16(2):533-43
14742873
Plant Mol Biol. 2002 Jun-Jul;49(3-4):373-85
12036261
J Plant Physiol. 2009 Mar 15;166(5):548-53
18771815
Biochem Biophys Res Commun. 2004 Aug 13;321(1):172-8
15358231
Plant J. 2003 Jun;34(5):733-9
12787253
Funct Integr Genomics. 2006 Jan;6(1):47-59
16200395
Plant J. 2005 Nov;44(3):382-95
16236149
Plant J. 1995 Jul;8(1):87-96
7655509
BMC Plant Biol. 2007 Nov 06;7:59
17986329