title: The relationship between the plant-encoded RNA-dependent RNA polymerase 1 and alternative oxidase in tomato basal defense against Tobacco mosaic virus.
abstract: Salicylic acid (SA) plays a critical role in plant defense against pathogen attack. The SA-induced viral defense in plants is distinct from the pathways mediating bacterial and fungal defense, which is pathogenesis-related protein-independent but involves an RNA-dependent RNA polymerase 1 (RDR1)-mediated RNA silencing mechanism and/or an alternative oxidase (AOX)-associated defense pathway. However, the relationship between these two viral defense-related pathways remains unclear. In this study, Tobacco mosaic virus (TMV) inoculation onto Solanum lycopersicum (tomato) leaves induced a rapid induction of the SlAOX1a transcript level as well as the total and CN-resistant respiration at 0.5 dpi, followed by an increase in SlRDR1 gene expression at 1 dpi in the upper uninoculated leaves. Silencing SlRDR1 using virus-induced gene silencing system significantly reduced SlRDR1 expression and tomato defense against TMV but had no evident effect on SlAOX1a transcription. Conversely, silencing SlAOX1a not only effectively reduced the AOX1a transcript level, but also blocked the TMV-induced SlRDR1 expression and decreased the basal defense against TMV. Furthermore, the application of an exogenous AOX activator on empty vector-silenced control plants greatly induced the accumulation of SlRDR1 and SlAOX1a transcript and reduced TMV viral RNA accumulation, but failed to have such effects on SlRDR1-silenced plants. Moreover, RDR1-overexpressed transgenic Nicotiana benthamiana plants enhanced defense against TMV than the empty vector-transformed plants, but these effects were not affected by the exogenous AOX activator or inhibitor. These results indicate that RDR1 is involved in the AOX-mediated defense pathway against TMV infection and plays a crucial role in enhancing RNA silencing to limit virus systemic spread.
authors.affiliation: Department of Horticulture Zijingang Campus, Zhejiang University, 866 Yuhangtang Road, Hangzhou, 310058, People's Republic of China.
authors.forename: Yang-Wen-Ke
authors.initials: YW
authors.lastname: Liao
authors.forename: Ya-Ru
authors.initials: YR
authors.lastname: Liu
authors.forename: Jia-Yang
authors.initials: JY
authors.lastname: Liang
authors.forename: Wen-Ping
authors.initials: WP
authors.lastname: Wang
authors.forename: Jie
authors.initials: J
authors.lastname: Zhou
authors.forename: Xiao-Jian
authors.initials: XJ
authors.lastname: Xia
authors.forename: Yan-Hong
authors.initials: YH
authors.lastname: Zhou
authors.forename: Jing-Quan
authors.initials: JQ
authors.lastname: Yu
authors.forename: Kai
authors.initials: K
authors.lastname: Shi
mesh_terms: D001483:Base Sequence; D019069:Cell Respiration; D020868:Gene Silencing; D054884:Host-Pathogen Interactions; D018551:Solanum lycopersicum / Q000201:enzymology* / Q000235:genetics / Q000821:virology; D024101:Mitochondrial Proteins / Q000378:metabolism*; D008969:Molecular Sequence Data; D010088:Oxidoreductases / Q000378:metabolism*; D010940:Plant Proteins / Q000378:metabolism*; D011190:Potassium Cyanide; D012324:RNA-Dependent RNA Polymerase / Q000378:metabolism*; D020239:Receptor Cross-Talk; D014027:Tobacco Mosaic Virus / Q000502:physiology*; D000099188:Alternative Oxidase
chemical_list: D024101:Mitochondrial Proteins; D010088:Oxidoreductases; D010940:Plant Proteins; D011190:Potassium Cyanide; D012324:RNA-Dependent RNA Polymerase; D000099188:Alternative Oxidase