title: Endoplasmic reticulum localization and activity of maize auxin biosynthetic enzymes.
abstract: Auxin is a major growth hormone in plants and the first plant hormone to be discovered and studied. Active research over >60 years has shed light on many of the molecular mechanisms of its action including transport, perception, signal transduction, and a variety of biosynthetic pathways in various species, tissues, and developmental stages. The complexity and redundancy of the auxin biosynthetic network and enzymes involved raises the question of how such a system, producing such a potent agent as auxin, can be appropriately controlled at all. Here it is shown that maize auxin biosynthesis takes place in microsomal as well as cytosolic cellular fractions from maize seedlings. Most interestingly, a set of enzymes shown to be involved in auxin biosynthesis via their activity and/or mutant phenotypes and catalysing adjacent steps in YUCCA-dependent biosynthesis are localized to the endoplasmic reticulum (ER). Positioning of auxin biosynthetic enzymes at the ER could be necessary to bring auxin biosynthesis in closer proximity to ER-localized factors for transport, conjugation, and signalling, and allow for an additional level of regulation by subcellular compartmentation of auxin action. Furthermore, it might provide a link to ethylene action and be a factor in hormonal cross-talk as all five ethylene receptors are ER localized.
authors.affiliation: Biological and Medical Sciences, Oxford Brookes University, Oxford OX3 0BP, UK vkriechbaumer@brookes.ac.uk.
authors.forename: Verena
authors.initials: V
authors.lastname: Kriechbaumer
authors.affiliation: Department of Molecular Biology, Institute of Nanosensor and Biotechnology, Dankook University, Yongin-si 448-701, South Korea.
authors.forename: Hyesu
authors.initials: H
authors.lastname: Seo
authors.affiliation: Department of Molecular Biology, Institute of Nanosensor and Biotechnology, Dankook University, Yongin-si 448-701, South Korea.
authors.forename: Woong June
authors.initials: WJ
authors.lastname: Park
authors.affiliation: Biological and Medical Sciences, Oxford Brookes University, Oxford OX3 0BP, UK.
authors.forename: Chris
authors.initials: C
authors.lastname: Hawes
mesh_terms: D018548:Cotyledon / Q000201:enzymology / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism; D007210:Indoleacetic Acids / Q000378:metabolism*; D007211:Indoles / Q000378:metabolism*; D008861:Microsomes / Q000378:metabolism; D010937:Plant Growth Regulators / Q000378:metabolism*; D018517:Plant Roots / Q000201:enzymology / Q000378:metabolism; D036226:Seedlings / Q000201:enzymology / Q000378:metabolism; D014364:Tryptophan / Q000378:metabolism*; D003313:Zea mays / Q000201:enzymology / Q000378:metabolism*
chemical_list: D007210:Indoleacetic Acids; D007211:Indoles; D010937:Plant Growth Regulators; C008122:indol-3-yl pyruvic acid; D014364:Tryptophan
keywords: Auxin biosynthesis; YUCCA; Zea mays.; compartmentation; endoplasmic reticulum; localization; maize