title: NPH4/ARF7 and ARF19 promote leaf expansion and auxin-induced lateral root formation.
abstract: Auxin response factors (ARFs) bind auxin response promoter elements and mediate transcriptional responses to auxin. Five of the 22 ARF genes in Arabidopsis thaliana encode ARFs with glutamine-rich middle domains. Four of these can activate transcription and have been ascribed developmental functions. We show that ARF19, the fifth Q-rich ARF, also activates transcription. Mutations in ARF19 have little effect on their own, but in combination with mutations in NPH4/ARF7, encoding the most closely related ARF, they cause several phenotypes including a drastic decrease in lateral and adventitious root formation and a decrease in leaf cell expansion. These results indicate that auxin induces lateral roots and leaf expansion by activating NPH4/ARF7 and ARF19. Auxin induces the ARF19 gene, and NPH4/ARF7 and ARF19 together are required for expression of one of the arf19 mutant alleles, suggesting that a positive feedback loop regulates leaf expansion and/or lateral root induction.
authors.affiliation: Department of Biology, University of North Carolina at Chapel Hill, CB no. 3280, Coker Hall, Chapel Hill, NC 27599-3280, USA.
authors.forename: Jill C
authors.initials: JC
authors.lastname: Wilmoth
authors.forename: Shucai
authors.initials: S
authors.lastname: Wang
authors.forename: Shiv B
authors.initials: SB
authors.lastname: Tiwari
authors.forename: Atul D
authors.initials: AD
authors.lastname: Joshi
authors.forename: Gretchen
authors.initials: G
authors.lastname: Hagen
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Guilfoyle
authors.forename: Jose M
authors.initials: JM
authors.lastname: Alonso
authors.forename: Joseph R
authors.initials: JR
authors.lastname: Ecker
authors.forename: Jason W
authors.initials: JW
authors.lastname: Reed
mesh_terms: D017360:Arabidopsis / Q000235:genetics* / Q000254:growth & development*; D029681:Arabidopsis Proteins / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D018506:Gene Expression Regulation, Plant; D007210:Indoleacetic Acids / Q000494:pharmacology / Q000502:physiology; D010641:Phenotype; D018515:Plant Leaves / Q000254:growth & development*; D018517:Plant Roots / Q000254:growth & development*; D015534:Trans-Activators / Q000502:physiology*; D014157:Transcription Factors / Q000502:physiology*; D014158:Transcription, Genetic
chemical_list: C503426:ARF19 protein, Arabidopsis; C503425:ARF7 protein, Arabidopsis; D029681:Arabidopsis Proteins; D007210:Indoleacetic Acids; D015534:Trans-Activators; D014157:Transcription Factors; C030737:indoleacetic acid