title: The etr1-2 mutation in Arabidopsis thaliana affects the abscisic acid, auxin, cytokinin and gibberellin metabolic pathways during maintenance of seed dormancy, moist-chilling and germination.
abstract: In Arabidopsis thaliana, the etr1-2 mutation confers dominant ethylene insensitivity and results in a greater proportion of mature seeds that exhibit dormancy compared with mature seeds of the wild-type. We investigated the impact of the etr1-2 mutation on other plant hormones by analyzing the profiles of four classes of plant hormones and their metabolites by HPLC-ESI/MS/MS in mature seeds of wild-type and etr1-2 plants. Hormone metabolites were analyzed in seeds imbibed immediately under germination conditions, in seeds subjected to a 7-day moist-chilling (stratification) period, and during germination/early post-germinative growth. Higher than wild-type levels of abscisic acid (ABA) appeared to contribute, at least in part, to the greater incidence of dormancy in mature seeds of etr1-2. The lower levels of abscisic acid glucose ester (ABA-GE) in etr1-2 seeds compared with wild-type seeds under germination conditions (with and without moist-chilling treatments) suggest that reduced metabolism of ABA to ABA-GE likely contributed to the accumulation of ABA during germination in the mutant. The mutant seeds exhibited generally higher auxin levels and a large build-up of indole-3-aspartate when placed in germination conditions following moist-chilling. The mutant manifested increased levels of cytokinin glucosides through zeatin-O-glucosylation (Z-O-Glu). The resulting increase in Z-O-Glu was the largest and most consistent change associated with the ETR1 gene mutation. There were more gibberellins (GA) and at higher concentrations in the mutant than in wild-type. Our results suggest that ethylene signaling modulates the metabolism of all the other plant hormone pathways in seeds. Additionally, the hormone profiles of etr1-2 seed during germination suggest a requirement for higher than wild-type levels of GA to promote germination in the absence of a functional ethylene signaling pathway.
authors.affiliation: Department of Biological Sciences, Simon Fraser University, Burnaby, BC, Canada V5A 1S6.
authors.forename: Sheila D S
authors.initials: SD
authors.lastname: Chiwocha
authors.forename: Adrian J
authors.initials: AJ
authors.lastname: Cutler
authors.forename: Suzanne R
authors.initials: SR
authors.lastname: Abrams
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Ambrose
authors.forename: Jenny
authors.initials: J
authors.lastname: Yang
authors.forename: Andrew R S
authors.initials: AR
authors.lastname: Ross
authors.forename: Allison R
authors.initials: AR
authors.lastname: Kermode
mesh_terms: D000040:Abscisic Acid / Q000378:metabolism; D017360:Arabidopsis / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000502:physiology*; D003583:Cytokinins / Q000378:metabolism; D018525:Germination / Q000502:physiology; D005875:Gibberellins / Q000378:metabolism; D007210:Indoleacetic Acids / Q000378:metabolism; D009154:Mutation; D010937:Plant Growth Regulators / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000235:genetics* / Q000502:physiology*; D012639:Seeds / Q000502:physiology; D013997:Time Factors
chemical_list: D029681:Arabidopsis Proteins; D003583:Cytokinins; C494590:ETR1 protein, Arabidopsis; D005875:Gibberellins; D007210:Indoleacetic Acids; D010937:Plant Growth Regulators; D011956:Receptors, Cell Surface; D000040:Abscisic Acid