title: Sites and regulation of auxin biosynthesis in Arabidopsis roots.
abstract: Auxin has been shown to be important for many aspects of root development, including initiation and emergence of lateral roots, patterning of the root apical meristem, gravitropism, and root elongation. Auxin biosynthesis occurs in both aerial portions of the plant and in roots; thus, the auxin required for root development could come from either source, or both. To monitor putative internal sites of auxin synthesis in the root, a method for measuring indole-3-acetic acid (IAA) biosynthesis with tissue resolution was developed. We monitored IAA synthesis in 0.5- to 2-mm sections of Arabidopsis thaliana roots and were able to identify an important auxin source in the meristematic region of the primary root tip as well as in the tips of emerged lateral roots. Lower but significant synthesis capacity was observed in tissues upward from the tip, showing that the root contains multiple auxin sources. Root-localized IAA synthesis was diminished in a cyp79B2 cyp79B3 double knockout, suggesting an important role for Trp-dependent IAA synthesis pathways in the root. We present a model for how the primary root is supplied with auxin during early seedling development.
authors.affiliation: Umeå Plant Science Center, Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, SE-901 83, Umeå, Sweden.
authors.forename: Karin
authors.initials: K
authors.lastname: Ljung
authors.forename: Anna K
authors.initials: AK
authors.lastname: Hull
authors.forename: John
authors.initials: J
authors.lastname: Celenza
authors.forename: Masashi
authors.initials: M
authors.lastname: Yamada
authors.forename: Mark
authors.initials: M
authors.lastname: Estelle
authors.forename: Jennifer
authors.initials: J
authors.lastname: Normanly
authors.forename: Göran
authors.initials: G
authors.lastname: Sandberg
mesh_terms: D017360:Arabidopsis / Q000254:growth & development* / Q000378:metabolism*; D001681:Biological Assay / Q000379:methods; D002454:Cell Differentiation / Q000235:genetics; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics / Q000378:metabolism; D018506:Gene Expression Regulation, Plant / Q000235:genetics; D006131:Growth Inhibitors / Q000494:pharmacology; D007210:Indoleacetic Acids / Q000032:analysis / Q000378:metabolism*; D018519:Meristem / Q000254:growth & development / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D018517:Plant Roots / Q000737:chemistry / Q000254:growth & development* / Q000378:metabolism*; D036226:Seedlings / Q000254:growth & development / Q000378:metabolism
chemical_list: D006131:Growth Inhibitors; D007210:Indoleacetic Acids; C030737:indoleacetic acid; D003577:Cytochrome P-450 Enzyme System; C471053:cytochrome P-450 CYP79B2, Sinapis alba; C471054:cytochrome P-450 CYP79B3, Sinapis alba