title: G-protein-coupled alpha2A-adrenoreceptor agonists differentially alter citrus leaf and fruit abscission by affecting expression of ACC synthase and ACC oxidase.
abstract: Temporal and spatial expression patterns of genes encoding 1-aminocyclopropane-1-carboxylate (ACC) synthase (ACS1 and ACS2) and ACC oxidase (ACO), ACC concentration, and ethylene production in leaves and fruit of 'Valencia' orange (Citrus sinensis [L.] Osbeck) were examined in relation to differential abscission after treatment with 2-chloroethylphosphonic acid (ethephon) alone or in combination with guanfacine or clonidine, two G-protein-coupled alpha(2A)-adrenoreceptor selective agonists. Guanfacine and clonidine markedly reduced ethephon-enhanced leaf abscission, but had little effect on ethephon-enhanced fruit loosening. Ethephon-enhanced fruit and leaf ethylene production, and ACC concentration in fruit abscission zones, fruit peel, leaf abscission zones, and leaf blades were decreased by guanfacine. Guanfacine reduced ethephon-enhanced expression of ACS1 and ACO genes in leaf abscission zones and blades, but to a lesser extent in fruit abscission zones. The expression pattern of the ACS2 gene, however, was not associated with abscission. The results demonstrate that differential expression of ACS1 and ACO genes is associated with reduction of ethephon-enhanced leaf abscission by guanfacine, and suggest a link between G-protein-related signalling and abscission.
authors.affiliation: University of Florida, Institute of Food and Agricultural Sciences, Citrus Research and Education Center, 700 Experiment Station Road, Lake Alfred, FL 33850-2299, USA.
authors.forename: Rongcai
authors.initials: R
authors.lastname: Yuan
authors.forename: Zhencai
authors.initials: Z
authors.lastname: Wu
authors.forename: Igor A
authors.initials: IA
authors.lastname: Kostenyuk
authors.forename: Jacqueline K
authors.initials: JK
authors.lastname: Burns
mesh_terms: D058647:Adrenergic alpha-2 Receptor Agonists; D000594:Amino Acid Oxidoreductases / Q000378:metabolism*; D002957:Citrus / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D003000:Clonidine / Q000494:pharmacology; D005638:Fruit / Q000378:metabolism / Q000502:physiology; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects / Q000502:physiology; D018506:Gene Expression Regulation, Plant / Q000187:drug effects / Q000502:physiology*; D016316:Guanfacine / Q000494:pharmacology; D008190:Lyases / Q000378:metabolism*; D009943:Organophosphorus Compounds / Q000494:pharmacology; D010937:Plant Growth Regulators / Q000494:pharmacology; D018515:Plant Leaves / Q000378:metabolism / Q000502:physiology; D011720:Pyrazoles / Q000494:pharmacology
chemical_list: D058647:Adrenergic alpha-2 Receptor Agonists; D009943:Organophosphorus Compounds; D010937:Plant Growth Regulators; D011720:Pyrazoles; D016316:Guanfacine; C018378:5-chloro-3-methyl-4-nitro-1H-pyrazole; D000594:Amino Acid Oxidoreductases; C059460:1-aminocyclopropane-1-carboxylic acid oxidase; D008190:Lyases; C021773:1-aminocyclopropanecarboxylate synthase; D003000:Clonidine; C005073:ethephon