title: Brassinosteroids regulate the differential growth of Arabidopsis hypocotyls through auxin signaling components IAA19 and ARF7.
abstract: Brassinosteroids (BRs) are an important class of phytohormones which regulates a wide range of physiological processes. Genetic and physiological studies have revealed that BR responses usually depend on an intact auxin signaling pathway. Here, we demonstrate that high BR concentration or enhanced BR signaling induce the differential growth of etiolated hypocotyls and result in the morphological changes, while auxin-resistant mutants, msg2 (dominant mutant of IAA19) and arf7, are insensitive to the BR effect and can partially suppress the phenotype of bzr1-D (dominant mutant of BZR1 with enhanced BR signaling). Interestingly, BZR1 protein can directly bind to the promoter regions of both IAA19 and ARF7, indicating that IAA19 and ARF7 mediate the BR-induced differential growth by serving as direct targets of BZR1. Systemic microarray analysis revealed that a number of BR-responsive genes showed reduced BR response in msg2, confirming that BR employs auxin signaling components IAA19 and ARF7 to modulate the specific downstream processes. These results provide informative clues on the crosstalk of BR-auxin signaling and the mechanisms of BR-auxin effects in regulating differential growth.
authors.affiliation: National Key Laboratory of Plant Molecular Genetics, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 300 Fenglin Road, 200032 Shanghai, China.
authors.forename: Xiao-Yi
authors.initials: XY
authors.lastname: Zhou
authors.forename: Li
authors.initials: L
authors.lastname: Song
authors.forename: Hong-Wei
authors.initials: HW
authors.lastname: Xue
mesh_terms: D017360:Arabidopsis / Q000166:cytology / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D060406:Brassinosteroids / Q000494:pharmacology*; D004268:DNA-Binding Proteins; D003624:Darkness; D004843:Epistasis, Genetic / Q000187:drug effects; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D017343:Genes, Plant / Q000235:genetics; D018546:Hypocotyl / Q000166:cytology / Q000187:drug effects / Q000254:growth & development* / Q000378:metabolism; D007210:Indoleacetic Acids / Q000378:metabolism*; D008954:Models, Biological; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D009687:Nuclear Proteins / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding / Q000187:drug effects / Q000235:genetics; D036226:Seedlings / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: C503425:ARF7 protein, Arabidopsis; D029681:Arabidopsis Proteins; C454444:BZR1 protein, Arabidopsis; D060406:Brassinosteroids; D004268:DNA-Binding Proteins; C483308:IAA19 protein, Arabidopsis; D007210:Indoleacetic Acids; D009687:Nuclear Proteins; D014157:Transcription Factors
keywords: ARF7; Arabidopsis; IAA19; auxin; brassinosteroids (BRs); differential growth