title: Auxin overproduction in shoots cannot rescue auxin deficiencies in Arabidopsis roots.
abstract: Auxin plays an essential role in root development. It has been a long-held dogma that auxin required for root development is mainly transported from shoots into roots by polarly localized auxin transporters. However, it is known that auxin is also synthesized in roots. Here we demonstrate that a group of YUCCA (YUC) genes, which encode the rate-limiting enzymes for auxin biosynthesis, plays an essential role in Arabidopsis root development. Five YUC genes (YUC3, YUC5, YUC7, YUC8 and YUC9) display distinct expression patterns during root development. Simultaneous inactivation of the five YUC genes (yucQ mutants) leads to the development of very short and agravitropic primary roots. The yucQ phenotypes are rescued by either adding 5 nM of the natural auxin, IAA, in the growth media or by expressing a YUC gene in the roots of yucQ. Interestingly, overexpression of a YUC gene in shoots in yucQ causes the characteristic auxin overproduction phenotypes in shoots; however, the root defects of yucQ are not rescued. Our data demonstrate that localized auxin biosynthesis in roots is required for normal root development and that auxin transported from shoots is not sufficient for supporting root elongation and root gravitropic responses.
authors.affiliation: Section of Cell and Developmental Biology, University of California at San Diego, La Jolla, CA 92093-0116, USA.
authors.forename: Qingguo
authors.initials: Q
authors.lastname: Chen
authors.affiliation: Section of Cell and Developmental Biology, University of California at San Diego, La Jolla, CA 92093-0116, USA.
authors.forename: Xinhua
authors.initials: X
authors.lastname: Dai
authors.affiliation: Section of Cell and Developmental Biology, University of California at San Diego, La Jolla, CA 92093-0116, USA.
authors.forename: Henrique
authors.initials: H
authors.lastname: De-Paoli
authors.affiliation: Section of Cell and Developmental Biology, University of California at San Diego, La Jolla, CA 92093-0116, USA.
authors.forename: Youfa
authors.initials: Y
authors.lastname: Cheng
authors.affiliation: RIKEN Center for Sustainable Resource Science, Yokohama, Kanagawa, 230-0045 Japan.
authors.forename: Yumiko
authors.initials: Y
authors.lastname: Takebayashi
authors.affiliation: RIKEN Center for Sustainable Resource Science, Yokohama, Kanagawa, 230-0045 Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Kasahara
authors.affiliation: RIKEN Center for Sustainable Resource Science, Yokohama, Kanagawa, 230-0045 Japan.
authors.forename: Yuji
authors.initials: Y
authors.lastname: Kamiya
authors.affiliation: Section of Cell and Developmental Biology, University of California at San Diego, La Jolla, CA 92093-0116, USA yundezhao@ucsd.edu.
authors.forename: Yunde
authors.initials: Y
authors.lastname: Zhao
mesh_terms: D017360:Arabidopsis / Q000166:cytology / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D001692:Biological Transport; D018506:Gene Expression Regulation, Plant; D018522:Gravitropism; D007210:Indoleacetic Acids / Q000378:metabolism*; D009154:Mutation; D009928:Organ Specificity; D010105:Oxygenases / Q000235:genetics / Q000378:metabolism; D010641:Phenotype; D010937:Plant Growth Regulators / Q000378:metabolism*; D018517:Plant Roots / Q000166:cytology / Q000235:genetics / Q000254:growth & development / Q000502:physiology; D018520:Plant Shoots / Q000166:cytology / Q000235:genetics / Q000254:growth & development / Q000502:physiology
chemical_list: D029681:Arabidopsis Proteins; D007210:Indoleacetic Acids; D010937:Plant Growth Regulators; D010105:Oxygenases; C422746:YUC protein, Arabidopsis
keywords: Auxin; Biosynthesis; Hormone; Root development; Transport