Auxin is a major growth hormone in plants and the first plant hormone to be discovered and studied. Active research over more than sixty 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 how such a system, producing such a potent agent as auxin, can be appropriately controlled at all. Here we show 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 localised to the endoplasmic reticulum (ER). Positioning of auxin biosynthetic enzymes at the endoplasmic reticulum could be necessary to bring auxin biosynthesis in closer proximity to ER-localised 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 crosstalk as all five ethylene receptors are ER-localised.
Kriechbaumer, Verena Seo, HPark, WHawes, Chris
Faculty of Health and Life Sciences\Department of Biological and Medical Sciences
Year of publication: 2015Date of RADAR deposit: 2016-07-06