title: The Arabidopsis mutant alh1 illustrates a cross talk between ethylene and auxin.
abstract: Ethylene or its precursor 1-aminocyclopropane-1-carboxylic acid (ACC) can stimulate hypocotyl elongation in light-grown Arabidopsis seedlings. A mutant, designated ACC-related long hypocotyl 1 (alh1), that displayed a long hypocotyl in the light in the absence of the hormone was characterized. Etiolated alh1 seedlings overproduced ethylene and had an exaggerated apical hook and a thicker hypocotyl, although no difference in hypocotyl length was observed when compared with wild type. Alh1 plants were less sensitive to ethylene, as reflected by reduction of ACC-mediated inhibition of hypocotyl growth in the dark and delay in flowering and leaf senescence. Alh1 also had an altered response to auxin, whereas auxin levels in whole alh1 seedlings remained unaffected. In contrast to wild type, alh1 seedlings showed a limited hypocotyl elongation when treated with indole-3-acetic acid. Alh1 roots had a faster response to gravity. Furthermore, the hypocotyl elongation of alh1 and of ACC-treated wild type was reverted by auxin transport inhibitors. In addition, auxin up-regulated genes were ectopically expressed in hypocotyls upon ACC treatment, suggesting that the ethylene response is mediated by auxins. Together, these data indicate that alh1 is altered in the cross talk between ethylene and auxins, probably at the level of auxin transport.
authors.affiliation: Department of Plant Systems Biology, Flanders Interuniversity Institute for Biotechnology, Ghent University, KL Ledeganckstraat 35, B-9000 Ghent, Belgium.
authors.forename: Filip
authors.initials: F
authors.lastname: Vandenbussche
authors.forename: Jan
authors.initials: J
authors.lastname: Smalle
authors.forename: Jie
authors.initials: J
authors.lastname: Le
authors.forename: Nelson José Madeira
authors.initials: NJ
authors.lastname: Saibo
authors.forename: Annelies
authors.initials: A
authors.lastname: De Paepe
authors.forename: Laury
authors.initials: L
authors.lastname: Chaerle
authors.forename: Olaf
authors.initials: O
authors.lastname: Tietz
authors.forename: Raphael
authors.initials: R
authors.lastname: Smets
authors.forename: Lucas J J
authors.initials: LJ
authors.lastname: Laarhoven
authors.forename: Frans J M
authors.initials: FJ
authors.lastname: Harren
authors.forename: Harry
authors.initials: H
authors.lastname: Van Onckelen
authors.forename: Klaus
authors.initials: K
authors.lastname: Palme
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Verbelen
authors.forename: Dominique
authors.initials: D
authors.lastname: Van Der Straeten
mesh_terms: D000598:Amino Acids, Cyclic / Q000378:metabolism; D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D002874:Chromosome Mapping; D003624:Darkness; D005030:Ethylenes / Q000096:biosynthesis / Q000494:pharmacology*; D018522:Gravitropism / Q000502:physiology; D018466:Gravity Sensing / Q000502:physiology; D018546:Hypocotyl / Q000235:genetics / Q000254:growth & development; D007210:Indoleacetic Acids / Q000096:biosynthesis / Q000494:pharmacology*; D008027:Light; D009154:Mutation; D010641:Phenotype; D018517:Plant Roots / Q000235:genetics / Q000502:physiology; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics
chemical_list: D000598:Amino Acids, Cyclic; D005030:Ethylenes; D007210:Indoleacetic Acids; C023863:1-aminocyclopropane-1-carboxylic acid; C036216:ethylene