title: Tracheophytes Contain Conserved Orthologs of a Basic Helix-Loop-Helix Transcription Factor That ModulateROOT HAIR SPECIFICGenes.
abstract: ROOT HAIR SPECIFIC(RHS) genes, which contain the root hair-specificcis-element (RHE) in their regulatory regions, function in root hair morphogenesis. Here, we demonstrate that anArabidopsis thalianabasic helix-loop-helix transcription factor, ROOT HAIR DEFECTVE SIX-LIKE4 (RSL4), directly binds to the RHE in vitro and in vivo, upregulatesRHSgenes, and stimulates root hair formation in Arabidopsis. Orthologs of RSL4 from a eudicot (poplar [Populus trichocarpa]), a monocot (rice [Oryza sativa]), and a lycophyte (Selaginella moellendorffii) each restored root hair growth in the Arabidopsisrsl4mutant. In addition, the rice andS. moellendorffiiRSL4 orthologs bound to the RHE in in vitro and in vivo assays. TheRSL4orthologous genes contain RHEs in their promoter regions, and RSL4 was able to bind to its own RHEs in vivo and amplify its own expression. This process likely provides a positive feedback loop for sustainable root hair growth. WhenRSL4and its orthologs were expressed in cells in non-root-hair positions, they induced ectopic root hair growth, indicating that these genes are sufficient to specify root hair formation. Our results suggest that RSL4 mediates root hair formation by regulatingRHSgenes and that this mechanism is conserved throughout the tracheophyte (vascular plant) lineage.
authors.affiliation: Department of Biological Sciences and Plant Genomics and Breeding Institute, Seoul National University, Seoul 151-742, Korea.
authors.forename: Youra
authors.identifier: 0000-0002-6368-6113
authors.initials: Y
authors.lastname: Hwang
authors.affiliation: Department of Biological Sciences and Plant Genomics and Breeding Institute, Seoul National University, Seoul 151-742, Korea.
authors.forename: Hee-Seung
authors.identifier: 0000-0003-4485-5919
authors.initials: HS
authors.lastname: Choi
authors.affiliation: Department of Biological Sciences and Plant Genomics and Breeding Institute, Seoul National University, Seoul 151-742, Korea.
authors.forename: Hyun-Min
authors.initials: HM
authors.lastname: Cho
authors.affiliation: Department of Biological Sciences and Plant Genomics and Breeding Institute, Seoul National University, Seoul 151-742, Korea htcho@snu.ac.kr.
authors.forename: Hyung-Taeg
authors.identifier: 0000-0003-1743-3403
authors.initials: HT
authors.lastname: Cho
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000145:classification / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D051792:Basic Helix-Loop-Helix Proteins / Q000145:classification / Q000235:genetics* / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D018613:Microscopy, Confocal; D012275:Oryza / Q000235:genetics / Q000378:metabolism; D010802:Phylogeny; D018517:Plant Roots / Q000235:genetics* / Q000378:metabolism; D018514:Plant Structures / Q000235:genetics* / Q000378:metabolism; D030821:Plants, Genetically Modified; D032107:Populus / Q000235:genetics / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D032503:Selaginellaceae / Q000235:genetics / Q000378:metabolism; D012689:Sequence Homology, Nucleic Acid
chemical_list: D029681:Arabidopsis Proteins; D051792:Basic Helix-Loop-Helix Proteins; C548371:RSL4 protein, Arabidopsis