title: Strigolactone Signaling in Arabidopsis Regulates Shoot Development by Targeting D53-Like SMXL Repressor Proteins for Ubiquitination and Degradation.
abstract: Strigolactones (SLs) are carotenoid-derived phytohormones that control many aspects of plant development, including shoot branching, leaf shape, stem secondary thickening, and lateral root growth. In rice (Oryza sativa), SL signaling requires the degradation of DWARF53 (D53), mediated by a complex including D14 and D3, but in Arabidopsis thaliana, the components and mechanism of SL signaling involving the D3 ortholog MORE AXILLARY GROWTH2 (MAX2) are unknown. Here, we show that SL-dependent regulation of shoot branching in Arabidopsis requires three D53-like proteins, SUPPRESSOR OF MORE AXILLARY GROWTH2-LIKE6 (SMXL6), SMXL7, and SMXL8. The smxl6 smxl7 smxl8 triple mutant suppresses the highly branched phenotypes of max2 and the SL-deficient mutant max3. Overexpression of a mutant form of SMXL6 that is resistant to SL-induced ubiquitination and degradation enhances shoot branching. Exogenous application of the SL analog rac-GR24 causes ubiquitination and degradation of SMXL6, 7, and 8; this requires D14 and MAX2. D53-like SMXLs form complexes with MAX2 and TOPLESS-RELATED PROTEIN2 (TPR2) and interact with D14 in a GR24-responsive manner. Furthermore, D53-like SMXLs exhibit TPR2-dependent transcriptional repression activity and repress the expression of BRANCHED1. Our findings reveal that in Arabidopsis, D53-like SMXLs act with TPR2 to repress transcription and so allow lateral bud outgrowth but that SL-induced degradation of D53-like proteins activates transcription to inhibit outgrowth.
authors.affiliation: State Key Laboratory of Plant Genomics and National Center for Plant Gene Research (Beijing), Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China University of Chinese Academy of Sciences, Beijing 100039, China.
authors.forename: Lei
authors.identifier: http://orcid.org/0000-0002-0356-3592
authors.initials: L
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Plant Genomics and National Center for Plant Gene Research (Beijing), Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China.
authors.forename: Bing
authors.identifier: http://orcid.org/0000-0002-2759-1512
authors.initials: B
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Plant Genomics and National Center for Plant Gene Research (Beijing), Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China University of Chinese Academy of Sciences, Beijing 100039, China.
authors.forename: Liang
authors.initials: L
authors.lastname: Jiang
authors.affiliation: State Key Laboratory of Plant Genomics and National Center for Plant Gene Research (Beijing), Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China University of Chinese Academy of Sciences, Beijing 100039, China.
authors.forename: Xue
authors.initials: X
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Plant Genomics and National Center for Plant Gene Research (Beijing), Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China.
authors.forename: Xilong
authors.initials: X
authors.lastname: Li
authors.affiliation: State Key Laboratory of Plant Genomics and National Center for Plant Gene Research (Beijing), Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China University of Chinese Academy of Sciences, Beijing 100039, China.
authors.forename: Zefu
authors.initials: Z
authors.lastname: Lu
authors.affiliation: State Key Laboratory of Plant Genomics and National Center for Plant Gene Research (Beijing), Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China.
authors.forename: Xiangbing
authors.initials: X
authors.lastname: Meng
authors.affiliation: State Key Laboratory of Plant Genomics and National Center for Plant Gene Research (Beijing), Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China University of Chinese Academy of Sciences, Beijing 100039, China.
authors.forename: Yonghong
authors.initials: Y
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Plant Genomics and National Center for Plant Gene Research (Beijing), Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China School of Biological Sciences, University of Tasmania, Hobart 7001, Australia.
authors.forename: Steven M
authors.identifier: http://orcid.org/0000-0001-5661-9994
authors.initials: SM
authors.lastname: Smith
authors.affiliation: State Key Laboratory of Plant Genomics and National Center for Plant Gene Research (Beijing), Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China University of Chinese Academy of Sciences, Beijing 100039, China jyli@genetics.ac.cn.
authors.forename: Jiayang
authors.identifier: http://orcid.org/0000-0002-0487-6574
authors.initials: J
authors.lastname: Li
mesh_terms: D017360:Arabidopsis / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000378:metabolism*; D049452:Green Fluorescent Proteins / Q000378:metabolism; D007783:Lactones / Q000378:metabolism* / Q000494:pharmacology; D009154:Mutation / Q000235:genetics; D018515:Plant Leaves / Q000033:anatomy & histology / Q000187:drug effects; D018520:Plant Shoots / Q000254:growth & development*; D011485:Protein Binding / Q000187:drug effects; D059748:Proteolysis / Q000187:drug effects; D012097:Repressor Proteins / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D054875:Ubiquitination / Q000187:drug effects
chemical_list: D029681:Arabidopsis Proteins; D007783:Lactones; D012097:Repressor Proteins; D049452:Green Fluorescent Proteins