title: Activation of polyphenol oxidase in dormant wild oat caryopses by a seed-decay isolate of Fusarium avenaceum.
abstract: Incubation of dormant wild oat (Avena fatua L., isoline M73) caryopses for 1-3 days with Fusarium avenaceum seed-decay isolate F.a.1 induced activity of the plant defense enzyme polyphenol oxidase (PPO). Both extracts and leachates obtained from F.a.1-treated caryopses had decreased abundance of an ∼57 kDa antigenic PPO and increased abundance of antigenic PPOs ranging from ∼52 to 14 kDa, as compared to extracts and leachates from untreated caryopsis. Leachates from caryopsis incubated for 2 days with F.a.1 also had 5.1- and 7.5-fold more total PPO activity/g fwt and specific activity, respectively. Fractionation of leachate proteins by ion-exchange chromatography associated the majority of PPO activity with an ∼36 kDa protein from untreated caryopses and ∼36, 25, and 24 kDa proteins from F.a.1-treated caryopses. Predicted peptide sequences obtained from high-performance liquid chromatography-tandem mass spectrometry analyses indicated that the ∼57 and 36 kDa wild oat proteins had a strong similarity to wheat PPO. However, the 25 and 24 kDa proteins were most similar to a Chitinase and oxalate oxidase, respectively. Our results indicate that F.a.1-induced activation of latent PPO in wild oat caryopsis likely involves a cleavage mechanism allowing activated PPOs to be readily mobilized into their surrounding environment.
authors.affiliation: Biosciences Research Laboratory, Agricultural Research Service, US Department of Agriculture, 1605 Albrecht Boulevard, Fargo, North Dakota 58102-2765, USA. james.anderson@ars.usda.gov
authors.forename: James V
authors.initials: JV
authors.lastname: Anderson
authors.forename: E Patrick
authors.initials: EP
authors.lastname: Fuerst
authors.forename: Trisa
authors.initials: T
authors.lastname: Tedrow
authors.forename: Brent
authors.initials: B
authors.lastname: Hulke
authors.forename: Ann C
authors.initials: AC
authors.lastname: Kennedy
mesh_terms: D000595:Amino Acid Sequence; D004156:Catechol Oxidase / Q000032:analysis / Q000737:chemistry / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D004789:Enzyme Activation; D005670:Fusarium / Q000502:physiology*; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000302:isolation & purification; D006109:Poaceae / Q000201:enzymology*; D012639:Seeds / Q000201:enzymology* / Q000382:microbiology*; D053719:Tandem Mass Spectrometry
chemical_list: D010940:Plant Proteins; D004156:Catechol Oxidase