Auxin and light control of adventitious rooting in Arabidopsis require ARGONAUTE1.
Adventitious rooting is a quantitative genetic trait regulated by both environmental and endogenous factors. To better understand the physiological and molecular basis of adventitious rooting, we took advantage of two classes of Arabidopsis thaliana mutants altered in adventitious root formation: the superroot mutants, which spontaneously make adventitious roots, and the argonaute1 (ago1) mutants, which unlike superroot are barely able to form adventitious roots. The defect in adventitious rooting observed in ago1 correlated with light hypersensitivity and the deregulation of auxin homeostasis specifically in the apical part of the seedlings. In particular, a clear reduction in endogenous levels of free indoleacetic acid (IAA) and IAA conjugates was shown. This was correlated with a downregulation of the expression of several auxin-inducible GH3 genes in the hypocotyl of the ago1-3 mutant. We also found that the Auxin Response Factor17 (ARF17) gene, a potential repressor of auxin-inducible genes, was overexpressed in ago1-3 hypocotyls. The characterization of an ARF17-overexpressing line showed that it produced fewer adventitious roots than the wild type and retained a lower expression of GH3 genes. Thus, we suggest that ARF17 negatively regulates adventitious root formation in ago1 mutants by repressing GH3 genes and therefore perturbing auxin homeostasis in a light-dependent manner. These results suggest that ARF17 could be a major regulator of adventitious rooting in Arabidopsis.
Sorin
Céline
C
Laboratoire de Biologie Cellulaire, Institut National de la Recherche Agronomique, 78026 Versailles Cedex, France.
Bussell
John D
JD
Camus
Isabelle
I
Ljung
Karin
K
Kowalczyk
Mariusz
M
Geiss
Gaia
G
McKhann
Heather
H
Garcion
Christophe
C
Vaucheret
Hervé
H
Sandberg
Göran
G
Bellini
Catherine
C
D017360:Arabidopsis / Q000254:growth & development / Q000378:metabolism* / Q000528:radiation effects*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D060565:Argonaute Proteins; D015536:Down-Regulation / Q000235:genetics / Q000528:radiation effects; D018506:Gene Expression Regulation, Plant / Q000235:genetics / Q000528:radiation effects; D006706:Homeostasis / Q000235:genetics / Q000528:radiation effects; D007210:Indoleacetic Acids / Q000378:metabolism*; D008027:Light; D009154:Mutation / Q000502:physiology / Q000528:radiation effects; D010775:Photic Stimulation; D018517:Plant Roots / Q000254:growth & development / Q000378:metabolism* / Q000528:radiation effects*; D012333:RNA, Messenger / Q000378:metabolism; D036226:Seedlings / Q000254:growth & development / Q000378:metabolism / Q000528:radiation effects; D015534:Trans-Activators / Q000378:metabolism
C117457:AGO1 protein, Arabidopsis; D029681:Arabidopsis Proteins; D060565:Argonaute Proteins; D007210:Indoleacetic Acids; D012333:RNA, Messenger; D015534:Trans-Activators; C030737:indoleacetic acid