title: Characterization of a novel lipoxygenase-independent senescence mechanism in Alstroemeria peruviana floral tissue.
abstract: The role of lipoxygenase (lox) in senescence of Alstroemeria peruviana flowers was investigated using a combination of in vitro assays and chemical profiling of the lipid oxidation products generated. Phospholipids and galactolipids were extensively degraded during senescence in both sepals and petals and the ratio of saturated/unsaturated fatty acids increased. Lox protein levels and enzymatic activity declined markedly after flower opening. Stereochemical analysis of lox products showed that 13-lox was the major activity present in both floral tissues and high levels of 13-keto fatty acids were also synthesized. Lipid hydroperoxides accumulated in sepals, but not in petals, and sepals also had a higher chlorophyll to carotenoid ratio that favors photooxidation of lipids. Loss of membrane semipermeability was coincident for both tissue types and was chronologically separated from lox activity that had declined by over 80% at the onset of electrolyte leakage. Thus, loss of membrane function was not related to lox activity or accumulation of lipid hydroperoxides per se and differs in these respects from other ethylene-insensitive floral tissues representing a novel pattern of flower senescence.
authors.affiliation: Department of Plant Genetics and Biotechnology, Horticulture Research International, Wellesbourne, Warwickshire CV35 9EF, United Kingdom.
authors.forename: Michael K
authors.initials: MK
authors.lastname: Leverentz
authors.forename: Carol
authors.initials: C
authors.lastname: Wagstaff
authors.forename: Hilary J
authors.initials: HJ
authors.lastname: Rogers
authors.forename: Anthony D
authors.initials: AD
authors.lastname: Stead
authors.forename: Usawadee
authors.initials: U
authors.lastname: Chanasut
authors.forename: Helena
authors.initials: H
authors.lastname: Silkowski
authors.forename: Brian
authors.initials: B
authors.lastname: Thomas
authors.forename: Heiko
authors.initials: H
authors.lastname: Weichert
authors.forename: Ivo
authors.initials: I
authors.lastname: Feussner
authors.forename: Gareth
authors.initials: G
authors.lastname: Griffiths
mesh_terms: D000872:Anthocyanins / Q000378:metabolism; D000975:Antioxidants / Q000378:metabolism; D002338:Carotenoids / Q000378:metabolism; D002734:Chlorophyll / Q000378:metabolism; D004573:Electrolytes / Q000378:metabolism; D005227:Fatty Acids / Q000737:chemistry / Q000378:metabolism; D050356:Lipid Metabolism; D015227:Lipid Peroxidation; D008055:Lipids / Q000737:chemistry; D008084:Lipoxygenase / Q000378:metabolism*; D019684:Magnoliopsida / Q000201:enzymology* / Q000254:growth & development; D008968:Molecular Conformation; D010860:Pigments, Biological / Q000378:metabolism; D018547:Plant Stems / Q000201:enzymology*; D017382:Reactive Oxygen Species / Q000378:metabolism; D017392:Thiobarbituric Acid Reactive Substances / Q000378:metabolism
chemical_list: D000872:Anthocyanins; D000975:Antioxidants; D004573:Electrolytes; D005227:Fatty Acids; D008055:Lipids; D010860:Pigments, Biological; D017382:Reactive Oxygen Species; D017392:Thiobarbituric Acid Reactive Substances; D002734:Chlorophyll; D002338:Carotenoids; D008084:Lipoxygenase