title: Suppression of bamboo mosaic virus accumulation by a putative methyltransferase in Nicotiana benthamiana.
abstract: Bamboo mosaic virus (BaMV) is a 6.4-kb positive-sense RNA virus belonging to the genus Potexvirus of the family Flexiviridae. The 155-kDa viral replicase, the product of ORF1, comprises an N-terminal S-adenosyl-l-methionine (AdoMet)-dependent guanylyltransferase, a nucleoside triphosphatase/RNA 5'-triphosphatase, and a C-terminal RNA-dependent RNA polymerase (RdRp). To search for cellular factors potentially involved in the regulation of replication and/or transcription of BaMV, the viral RdRp domain was targeted as bait to screen against a leaf cDNA library of Nicotiana benthamiana using a yeast two-hybrid system. A putative methyltransferase (PNbMTS1) of 617 amino acid residues without an established physiological function was identified. Cotransfection of N. benthamiana protoplasts with a BaMV infectious clone and the PNbMTS1-expressing plasmid showed a PNbMTS1 dosage-dependent inhibitory effect on the accumulation of BaMV coat protein. Deletion of the N-terminal 36 amino acids, deletion of a predicted signal peptide or transmembrane segment, or mutations in the putative AdoMet-binding motifs of PNbMTS1 abolished the inhibitory effect. In contrast, suppression of PNbMTS1 by virus-induced gene silencing in N. benthamiana increased accumulation of the viral coat protein as well as the viral genomic RNA. Collectively, PNbMTS1 may function as an innate defense protein against the accumulation of BaMV through an uncharacterized mechanism.
authors.affiliation: Graduate Institute of Biotechnology, National Chung Hsing University, Taichung, Taiwan.
authors.forename: Chun-Wei
authors.initials: CW
authors.lastname: Cheng
authors.forename: Yi-Yuong
authors.initials: YY
authors.lastname: Hsiao
authors.forename: Hui-Chuan
authors.initials: HC
authors.lastname: Wu
authors.forename: Chi-Mau
authors.initials: CM
authors.lastname: Chuang
authors.forename: Jao-Shien
authors.initials: JS
authors.lastname: Chen
authors.forename: Ching-Hsiu
authors.initials: CH
authors.lastname: Tsai
authors.forename: Yau-Heiu
authors.initials: YH
authors.lastname: Hsu
authors.forename: Yao-Chu
authors.initials: YC
authors.lastname: Wu
authors.forename: Cheng-Cheng
authors.initials: CC
authors.lastname: Lee
authors.forename: Menghsiao
authors.initials: M
authors.lastname: Meng
mesh_terms: D000595:Amino Acid Sequence; D008780:Methyltransferases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D017863:Potexvirus / Q000201:enzymology* / Q000235:genetics; D011485:Protein Binding; D011523:Protoplasts / Q000378:metabolism; D013379:Substrate Specificity; D014026:Nicotiana / Q000821:virology*; D020798:Two-Hybrid System Techniques
chemical_list: D008780:Methyltransferases