title: Involvement of plasma membrane peroxidases and oxylipin pathway in the recovery from phytoplasma disease in apple (Malus domestica).
abstract: Apple trees (Malus domestica Borkh.) may be affected by apple proliferation (AP), caused by 'Candidatus Phytoplasma mali'. Some plants can spontaneously recover from the disease, which implies the disappearance of symptoms through a phenomenon known as recovery. In this article it is shown that NAD(P)H peroxidases of leaf plasma membrane-enriched fractions exhibited a higher activity in samples from both AP-diseased and recovered plants. In addition, an increase in endogenous SA was characteristic of the symptomatic plants, since its content increased in samples obtained from diseased apple trees. In agreement, phenylalanine ammonia lyase (PAL) activity, a key enzyme of the phenylpropanoid pathway, was increased too. Jasmonic acid (JA) increased only during recovery, in a phase subsequent to the pathological state, and in concomitance to a decline of salicylic acid (SA). Oxylipin pathway, responsible for JA synthesis, was not induced during the development of AP-disease, but it appeared to be stimulated when the recovery occurred. Accordingly, lipoxygenase (LOX) activity, detected in plasma membrane-enriched fractions, showed an increase in apple leaves obtained from recovered plants. This enhancement was paralleled by an increase of hydroperoxide lyase (HPL) activity, detected in leaf microsomes, albeit the latter enzyme was activated in either the disease or recovery conditions. Hence, a reciprocal antagonism between SA- and JA-pathways could be suggested as an effective mechanism by which apple plants react to phytoplasma invasions, thereby providing a suitable defense response leading to the establishment of the recovery phenomenon.
authors.affiliation: Department of Agricultural and Environmental Science, University of Udine, Udine 33100, Italy.
authors.forename: Sonia
authors.initials: S
authors.lastname: Patui
authors.forename: Alberto
authors.initials: A
authors.lastname: Bertolini
authors.forename: Luisa
authors.initials: L
authors.lastname: Clincon
authors.forename: Paolo
authors.initials: P
authors.lastname: Ermacora
authors.forename: Enrico
authors.initials: E
authors.lastname: Braidot
authors.forename: Angelo
authors.initials: A
authors.lastname: Vianello
authors.forename: Marco
authors.initials: M
authors.lastname: Zancani
mesh_terms: D000446:Aldehyde-Lyases / Q000378:metabolism; D002462:Cell Membrane / Q000201:enzymology*; D002734:Chlorophyll / Q000378:metabolism; D002934:Cinnamates / Q000032:analysis / Q000378:metabolism; D003517:Cyclopentanes / Q000032:analysis / Q000378:metabolism; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D008084:Lipoxygenase / Q000378:metabolism; D027845:Malus / Q000201:enzymology* / Q000235:genetics / Q000276:immunology / Q000502:physiology; D054883:Oxylipins / Q000032:analysis / Q000378:metabolism; D010544:Peroxidases / Q000235:genetics / Q000378:metabolism; D010650:Phenylalanine Ammonia-Lyase / Q000378:metabolism; D045582:Phytoplasma / Q000502:physiology*; D010935:Plant Diseases / Q000276:immunology; D010937:Plant Growth Regulators / Q000032:analysis / Q000378:metabolism; D018515:Plant Leaves / Q000201:enzymology / Q000235:genetics / Q000276:immunology / Q000502:physiology; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D020156:Salicylic Acid / Q000032:analysis / Q000378:metabolism
chemical_list: D002934:Cinnamates; D003517:Cyclopentanes; D054883:Oxylipins; D010937:Plant Growth Regulators; D010940:Plant Proteins; C029010:cinnamic acid; D002734:Chlorophyll; C011006:jasmonic acid; D003577:Cytochrome P-450 Enzyme System; D006861:Hydrogen Peroxide; D010544:Peroxidases; C021845:NAD+ peroxidase; C045195:NADPH peroxidase; D008084:Lipoxygenase; D000446:Aldehyde-Lyases; C054540:hydroperoxide lyase; D010650:Phenylalanine Ammonia-Lyase; D020156:Salicylic Acid