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Free Content NPH4/ARF7 and ARF19 promote leaf expansion and auxin-induced lateral root formation

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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.
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Keywords: ARF19; ARF7; NPH4; auxin; auxin response factor; lateral root

Document Type: Research Article

Affiliations: 1: Department of Biology, University of North Carolina at Chapel Hill, CB no. 3280, Coker Hall, Chapel Hill, NC 27599-3280, USA, 2: Department of Biochemistry, University of Missouri, Missouri, Columbia, Columbia, MO 65211, USA, and 3: Plant Biology Laboratory, The Salk Institute, La Jolla, CA 92186-5800, USA

Publication date: July 1, 2005

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