title: Terpene down-regulation triggers defense responses in transgenic orange leading to resistance against fungal pathogens.
abstract: Terpenoid volatiles are isoprene compounds that are emitted by plants to communicate with the environment. In addition to their function in repelling herbivores and attracting carnivorous predators in green tissues, the presumed primary function of terpenoid volatiles released from mature fruits is the attraction of seed-dispersing animals. Mature oranges (Citrus sinensis) primarily accumulate terpenes in peel oil glands, with d-limonene accounting for approximately 97% of the total volatile terpenes. In a previous report, we showed that down-regulation of a d-limonene synthase gene alters monoterpene levels in orange antisense (AS) fruits, leading to resistance against Penicillium digitatum infection. A global gene expression analysis of AS versus empty vector (EV) transgenic fruits revealed that the down-regulation of d-limonene up-regulated genes involved in the innate immune response. Basal levels of jasmonic acid were substantially higher in the EV compared with AS oranges. Upon fungal challenge, salicylic acid levels were triggered in EV samples, while jasmonic acid metabolism and signaling were drastically increased in AS orange peels. In nature, d-limonene levels increase in orange fruit once the seeds are fully viable. The inverse correlation between the increase in d-limonene content and the decrease in the defense response suggests that d-limonene promotes infection by microorganisms that are likely involved in facilitating access to the pulp for seed-dispersing frugivores.
authors.affiliation: Centro de Protección Vegetal y Biotecnología, Instituto Valenciano de Investigaciones Agrarias, Carretera Moncada-Náquera, 46113 Moncada, Valencia, Spain.
authors.forename: Ana
authors.initials: A
authors.lastname: Rodríguez
authors.forename: Takehiko
authors.initials: T
authors.lastname: Shimada
authors.forename: Magdalena
authors.initials: M
authors.lastname: Cervera
authors.forename: Berta
authors.initials: B
authors.lastname: Alquézar
authors.forename: José
authors.initials: J
authors.lastname: Gadea
authors.forename: Aurelio
authors.initials: A
authors.lastname: Gómez-Cadenas
authors.forename: Carlos José
authors.initials: CJ
authors.lastname: De Ollas
authors.forename: María Jesús
authors.initials: MJ
authors.lastname: Rodrigo
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Zacarías
authors.forename: Leandro
authors.initials: L
authors.lastname: Peña
mesh_terms: D032084:Citrus sinensis / Q000235:genetics* / Q000276:immunology / Q000382:microbiology*; D053138:Cyclohexenes / Q000378:metabolism* / Q000494:pharmacology; D003517:Cyclopentanes / Q000378:metabolism / Q000494:pharmacology; D015536:Down-Regulation; D051231:Farnesyltranstransferase / Q000235:genetics / Q000378:metabolism; D005638:Fruit / Q000187:drug effects / Q000235:genetics / Q000378:metabolism / Q000382:microbiology*; D018506:Gene Expression Regulation, Plant; D054884:Host-Pathogen Interactions / Q000502:physiology; D007113:Immunity, Innate / Q000235:genetics; D019753:Intramolecular Lyases / Q000235:genetics / Q000378:metabolism; D000077222:Limonene; D054883:Oxylipins / Q000378:metabolism / Q000494:pharmacology; D010407:Penicillium / Q000472:pathogenicity; D010935:Plant Diseases / Q000235:genetics / Q000382:microbiology; D030821:Plants, Genetically Modified; D015398:Signal Transduction / Q000235:genetics; D013729:Terpenes / Q000378:metabolism* / Q000494:pharmacology
chemical_list: D053138:Cyclohexenes; D003517:Cyclopentanes; D054883:Oxylipins; D013729:Terpenes; C011006:jasmonic acid; D000077222:Limonene; D051231:Farnesyltranstransferase; D019753:Intramolecular Lyases; C040265:pinene cyclase I