title: PAD4-dependent antibiosis contributes to the ssi2-conferred hyper-resistance to the green peach aphid.
abstract: Myzus persicae, commonly known as green peach aphid (GPA), is a sap-sucking insect with a broad host range. Arabidopsis thaliana responds to GPA infestation with elevated expression of the PHYTOALEXIN DEFICIENT4 (PAD4) gene. Previously, we had demonstrated that the loss of PAD4 gene function compromises Arabidopsis resistance to GPA. In contrast, a mutation in the Arabidopsis SUPPRESSOR OF SALICYLIC ACID INSENSITIVITY2 (SSI2) gene, which encodes a desaturase involved in lipid metabolism, resulted in hyper-resistance to GPA. We demonstrate here that PAD4 is required for the ssi2-dependent heightened resistance to GPA. Based on electrical monitoring of insect behavior and bioassays in which the insect was given a choice between the wild type and the ssi2 mutant, it is concluded that the ssi2-conferred resistance is not due to deterrence of insect settling or feeding from the phloem of the mutant. Instead, hyper-resistance in the ssi2 mutant results from heightened antibiosis that curtails insect reproduction. Petiole exudates collected from uninfested ssi2 plants contain elevated levels of an activity that interferes with aphid reproduction in synthetic diets. PAD4 was required for the accumulation of this antibiotic activity in petiole exudates, supporting the role of PAD4 in phloem-based resistance. Because PAD4 expression is not elevated in the ssi2 mutant, we suggest that basal PAD4 expression contributes to this antibiosis.
authors.affiliation: Department of Biological Sciences, University of North Texas, Denton, USA.
authors.forename: Joe
authors.initials: J
authors.lastname: Louis
authors.forename: Queena
authors.initials: Q
authors.lastname: Leung
authors.forename: Venkatramana
authors.initials: V
authors.lastname: Pegadaraju
authors.forename: John
authors.initials: J
authors.lastname: Reese
authors.forename: Jyoti
authors.initials: J
authors.lastname: Shah
mesh_terms: D000818:Animals; D000898:Antibiosis / Q000187:drug effects / Q000502:physiology*; D001042:Aphids / Q000502:physiology*; D017360:Arabidopsis / Q000187:drug effects / Q000201:enzymology / Q000235:genetics / Q000276:immunology / Q000469:parasitology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002265:Carboxylic Ester Hydrolases / Q000235:genetics / Q000378:metabolism*; D044943:Fatty Acid Desaturases / Q000235:genetics / Q000378:metabolism*; D005247:Feeding Behavior / Q000187:drug effects; D005298:Fertility / Q000187:drug effects; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D007113:Immunity, Innate / Q000187:drug effects; D008954:Models, Biological; D009154:Mutation / Q000235:genetics; D010935:Plant Diseases / Q000235:genetics / Q000276:immunology* / Q000469:parasitology; D053147:Plant Exudates / Q000378:metabolism; D018515:Plant Leaves / Q000187:drug effects / Q000378:metabolism; D011157:Population Dynamics; D027861:Prunus; D013229:Stearic Acids / Q000494:pharmacology; D013997:Time Factors
chemical_list: D029681:Arabidopsis Proteins; D053147:Plant Exudates; D013229:Stearic Acids; C031183:stearic acid; D044943:Fatty Acid Desaturases; C433487:stearoyl ACP desaturase, Arabidopsis; D002265:Carboxylic Ester Hydrolases; C400766:PAD4 protein, Arabidopsis