title: PhOBF1, a petunia ocs element binding factor, plays an important role in antiviral RNA silencing.
abstract: Virus-induced gene silencing (VIGS) is a common reverse genetics strategy for characterizing the function of genes in plants. The detailed mechanism governing RNA silencing efficiency triggered by viruses is largely unclear. Here, we reveal that a petunia (Petunia hybrida) ocs element binding factor, PhOBF1, one of the basic leucine zipper (bZIP) transcription factors, was up-regulated by Tobacco rattle virus (TRV) infection. Simultaneous silencing of PhOBF1 and a reporter gene, phytoene desaturase (PDS) or chalcone synthase (CHS), by TRV-based VIGS led to a failure of the development of leaf photobleaching or the white-corollas phenotype. PhOBF1 silencing caused down-regulation of RNA silencing-related genes, including RNA-dependent RNA polymerases (RDRs), Dicer-like RNase III enzymes (DCLs), and Argonautes (AGOs). After inoculation with the TRV-PhPDS, PhOBF1-RNAi lines exhibited a substantially impaired PDS silencing efficiency, whereas overexpression of PhOBF1 resulted in a recovery of the silencing phenotype (photobleaching) in systemic leaves. A compromised resistance to TRV and Tobacco mosaic virus was found in PhOBF1-RNAi lines, while PhOBF1-overexpressing lines displayed an enhanced resistance to their infections. Compared with wild-type plants, PhOBF1-silenced plants accumulated lower levels of free salicylic acid (SA), salicylic acid glucoside, and phenylalanine, contrarily to higher levels of those in plants overexpressing PhOBF1. Furthermore, transcripts of a number of genes associated with the shikimate and phenylpropanoid pathways were decreased or increased in PhOBF1-RNAi or PhOBF1-overexpressing lines, respectively. Taken together, the data suggest that PhOBF1 regulates TRV-induced RNA silencing efficiency through modulation of RDRs, DCLs, and AGOs mediated by the SA biosynthesis pathway.
authors.affiliation: Department of Landscape Architecture and Arts, Northwest A&F University, Yangling, Shaanxi 712100, China.|Department of Plant Sciences, University of California Davis, Davis, CA 95616, USA.
authors.forename: Daoyang
authors.initials: D
authors.lastname: Sun
authors.affiliation: Department of Landscape Architecture and Arts, Northwest A&F University, Yangling, Shaanxi 712100, China.
authors.forename: Shaohua
authors.initials: S
authors.lastname: Li
authors.affiliation: Department of Landscape Architecture and Arts, Northwest A&F University, Yangling, Shaanxi 712100, China.
authors.forename: Lixin
authors.initials: L
authors.lastname: Niu
authors.affiliation: Department of Plant Sciences, University of California Davis, Davis, CA 95616, USA.
authors.forename: Michael S
authors.initials: MS
authors.lastname: Reid
authors.affiliation: Department of Landscape Architecture and Arts, Northwest A&F University, Yangling, Shaanxi 712100, China.
authors.forename: Yanlong
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Department of Plant Sciences, University of California Davis, Davis, CA 95616, USA.|Crops Pathology and Genetic Research Unit, United States Department of Agriculture, Agricultural Research Service, Davis, CA 95616, USA.
authors.forename: Cai-Zhong
authors.initials: CZ
authors.lastname: Jiang
mesh_terms: D000217:Acyltransferases / Q000235:genetics* / Q000378:metabolism; D050976:Basic-Leucine Zipper Transcription Factors / Q000235:genetics* / Q000378:metabolism; D010088:Oxidoreductases / Q000235:genetics* / Q000378:metabolism; D032306:Petunia / Q000235:genetics* / Q000378:metabolism / Q000821:virology; D018515:Plant Leaves / Q000378:metabolism / Q000821:virology; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D034622:RNA Interference; D012328:RNA Viruses / Q000235:genetics*
chemical_list: D050976:Basic-Leucine Zipper Transcription Factors; D010940:Plant Proteins; D010088:Oxidoreductases; C022398:phytoene dehydrogenase; D000217:Acyltransferases; C020141:flavanone synthetase
keywords: Phenylpropanoid pathways; salicylic acid biosynthesis; shikimate; tobacco mosaic virus; tobacco rattle virus; transcription factor; virus-induced gene silencing.