title: SUPPRESSOR OF MORE AXILLARY GROWTH2 1 controls seed germination and seedling development in Arabidopsis.
abstract: Abiotic chemical signals discovered in smoke that are known as karrikins (KARs) and the endogenous hormone strigolactone (SL) control plant growth through a shared MORE AXILLARY GROWTH2 (MAX2)-dependent pathway. A SL biosynthetic pathway and candidate KAR/SL receptors have been characterized, but signaling downstream of MAX2 is poorly defined. A screen for genetic suppressors of the enhanced seed dormancy phenotype of max2 in Arabidopsis (Arabidopsis thaliana) led to identification of a suppressor of max2 1 (smax1) mutant. smax1 restores the seed germination and seedling photomorphogenesis phenotypes of max2 but does not affect the lateral root formation, axillary shoot growth, or senescence phenotypes of max2. Expression of three transcriptional markers of KAR/SL signaling, D14-LIKE2, KAR-UP F-BOX1, and INDOLE-3-ACETIC ACID INDUCIBLE1, is rescued in smax1 max2 seedlings. SMAX1 is a member of an eight-gene family in Arabidopsis that has weak similarity to HEAT SHOCK PROTEIN 101, which encodes a caseinolytic peptidase B chaperonin required for thermotolerance. SMAX1 and the SMAX1-like (SMXL) homologs are differentially expressed in Arabidopsis tissues. SMAX1 transcripts are most abundant in dry seed, consistent with its function in seed germination control. Several SMXL genes are up-regulated in seedlings treated with the synthetic SL GR24. SMAX1 and SMXL2 transcripts are reduced in max2 seedlings, which could indicate negative feedback regulation by KAR/SL signaling. smax1 seed and seedling growth mimics the wild type treated with KAR/SL, but smax1 seedlings are still responsive to 2H-furo[2,3-c]pyran-2-one (KAR2) or GR24. We conclude that SMAX1 is an important component of KAR/SL signaling during seed germination and seedling growth but is not necessary for all MAX2-dependent responses. We hypothesize that one or more SMXL proteins may also act downstream of MAX2 to control the diverse developmental responses to KARs and SLs.
authors.affiliation: Department of Genetics, University of Georgia, Athens, Georgia 30602, USA.
authors.forename: John P
authors.initials: JP
authors.lastname: Stanga
authors.forename: Steven M
authors.initials: SM
authors.lastname: Smith
authors.forename: Winslow R
authors.initials: WR
authors.lastname: Briggs
authors.forename: David C
authors.initials: DC
authors.lastname: Nelson
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D018506:Gene Expression Regulation, Plant; D018525:Germination / Q000235:genetics*; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D010641:Phenotype; D010802:Phylogeny; D036226:Seedlings / Q000235:genetics / Q000254:growth & development
chemical_list: D029681:Arabidopsis Proteins; D047908:Intracellular Signaling Peptides and Proteins; C587487:SMAX1 protein, Arabidopsis
references.citation: Plant J. 2001 Jul;27(1):25-35
references.pmid: 11489180
references.citation: Plant Cell Physiol. 2010 Jul;51(7):1095-103
references.pmid: 20403809
references.citation: Plant J. 2012 Sep;71(6):907-20
references.pmid: 22540368
references.citation: Proc Natl Acad Sci U S A. 2011 May 24;108(21):8897-902
references.pmid: 21555559
references.citation: Syst Biol. 2010 May;59(3):307-21
references.pmid: 20525638
references.citation: Proc Natl Acad Sci U S A. 2011 Dec 13;108(50):20242-7
references.pmid: 22123958
references.citation: J Exp Bot. 2011 May;62(8):2915-24
references.pmid: 21307387
references.citation: Science. 2012 Mar 16;335(6074):1348-51
references.pmid: 22422982
references.citation: Nature. 2008 Sep 11;455(7210):195-200
references.pmid: 18690207
references.citation: Development. 1997 Jan;124(1):33-44
references.pmid: 9006065
references.citation: Nat Genet. 2005 May;37(5):501-6
references.pmid: 15806101
references.citation: Curr Biol. 2006 Mar 21;16(6):553-63
references.pmid: 16546078
references.citation: New Phytol. 2012 Sep;195(4):857-871
references.pmid: 22738134
references.citation: Genes Cells. 2013 Feb;18(2):147-60
references.pmid: 23301669
references.citation: Trends Biochem Sci. 1996 Aug;21(8):289-96
references.pmid: 8772382
references.citation: Cell Res. 2013 Mar;23(3):436-9
references.pmid: 23381136
references.citation: New Phytol. 2011 May;190(3):545-9
references.pmid: 21638793
references.citation: Plant Sci. 2012 Feb;183:175-82
references.pmid: 22195591
references.citation: Plant Cell Physiol. 2012 Jan;53(1):107-17
references.pmid: 22173099
references.citation: Plant Physiol. 2009 Feb;149(2):863-73
references.pmid: 19074625
references.citation: Proc Natl Acad Sci U S A. 2000 Apr 11;97(8):4392-7
references.pmid: 10760305
references.citation: Plant Physiol. 2007 Dec;145(4):1471-83
references.pmid: 17951458
references.citation: Curr Biol. 2011 May 10;21(9):R338-45
references.pmid: 21549956
references.citation: Plant Physiol. 2012 Apr;158(4):1976-87
references.pmid: 22323776
references.citation: Proc Natl Acad Sci U S A. 2010 Apr 13;107(15):7095-100
references.pmid: 20351290
references.citation: Planta. 2005 Dec;223(1):105-13
references.pmid: 16034591
references.citation: Trends Plant Sci. 2009 Apr;14(4):206-13
references.pmid: 19285909
references.citation: Development. 2010 Sep 1;137(17):2905-13
references.pmid: 20667910
references.citation: Plant Physiol. 2012 Jul;159(3):1073-85
references.pmid: 22623516
references.citation: PLoS One. 2007 Aug 08;2(8):e718
references.pmid: 17684564
references.citation: New Phytol. 2013 May;198(3):866-874
references.pmid: 23425316
references.citation: Planta. 2011 Jan;233(1):209-16
references.pmid: 21080198
references.citation: Annu Rev Plant Biol. 2012;63:107-30
references.pmid: 22404467
references.citation: Plant Cell. 1994 Dec;6(12):1899-909
references.pmid: 7866032
references.citation: Plant Signal Behav. 2013 Mar;8(3):e23168
references.pmid: 23299321
references.citation: PLoS One. 2013;8(1):e54758
references.pmid: 23349965
references.citation: BMC Bioinformatics. 2006 Mar 30;7:179
references.pmid: 16571141
references.citation: Trends Plant Sci. 2013 Feb;18(2):72-83
references.pmid: 23182342
references.citation: Genes Dev. 1998 Oct 15;12(20):3236-51
references.pmid: 9784498
references.citation: Development. 2012 Apr;139(7):1285-95
references.pmid: 22357928
references.citation: Nucleic Acids Res. 2001 May 1;29(9):e45
references.pmid: 11328886
references.citation: Plant Cell. 2000 Jul;12(7):1213-27
references.pmid: 10899985
references.citation: Mol Plant. 2012 May;5(3):750-62
references.pmid: 22466576
references.citation: BMC Plant Biol. 2012 Sep 10;12:160
references.pmid: 22963533
references.citation: Plant J. 2013 Oct;76(1):1-9
references.pmid: 23773129
references.citation: Plant Cell. 2001 Aug;13(8):1779-90
references.pmid: 11487692
references.citation: PLoS Biol. 2013;11(1):e1001474
references.pmid: 23382651
references.citation: New Phytol. 2012 Dec;196(4):1208-1216
references.pmid: 23025475
references.citation: Trends Genet. 2002 Dec;18(12):613-5
references.pmid: 12446140
references.citation: Nature. 2008 Sep 11;455(7210):189-94
references.pmid: 18690209
references.citation: Genetics. 2001 Oct;159(2):777-85
references.pmid: 11606552
references.citation: Proc Natl Acad Sci U S A. 2013 May 14;110(20):8284-9
references.pmid: 23613584
references.citation: Plant Physiol. 2001 Nov;127(3):876-86
references.pmid: 11706170
references.citation: Plant Cell. 2005 Mar;17(3):746-59
references.pmid: 15705953
references.citation: Front Plant Sci. 2012 Dec 28;3:296
references.pmid: 23293648
references.citation: Plant Physiol. 2011 Feb;155(2):721-34
references.pmid: 21119044
references.citation: Nature. 1994 Dec 1;372(6505):475-8
references.pmid: 7984243
references.citation: Plant Signal Behav. 2011 Sep;6(9):1418-22
references.pmid: 22019642
references.citation: Plant Cell Environ. 2007 Dec;30(12):1523-34
references.pmid: 17986154
references.citation: Curr Biol. 2012 Nov 6;22(21):2032-6
references.pmid: 22959345
references.citation: Development. 2002 Mar;129(5):1131-41
references.pmid: 11874909
references.citation: Biosci Biotechnol Biochem. 2009 Nov;73(11):2460-5
references.pmid: 19897913