single silent substitution in the genome of Apple stem grooving virus causes symptom attenuation

• Published in: Journal of general virology 2003-09, Vol.84 (9), p.2579-2583
• Main Authors: Hirata, H, Lu, X, Yamaji, Y, Kagiwada, S, Ugaki, M, Namba, S
• Format: Article
• Language: English
• Subjects: Apple stem grooving virus; Blotting, Northern; Blotting, Western; Capsid Proteins - analysis; Genome, Viral; Malus domestica; mutants; Mutation; Open Reading Frames; Plant Diseases - virology; Plant Leaves - virology; Plant Viruses - genetics; Plant Viruses - isolation & purification; RNA Viruses - genetics; RNA Viruses - isolation & purification; RNA, Viral - analysis
• ISSN: 0022-1317; 1465-2099
• DOI: 10.1099/vir.0.19179-0

Laboratory of Bioresource Technology, Graduate School of Frontier Sciences, The University of Tokyo, 202 Bioscience Bldg, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8562, Japan Correspondence Shigetou Namba snamba{at}ims.u-tokyo.ac.jp Among randomly mutagenized clones derived from an infectious cDNA copy of genomic RNA of Apple stem grooving virus (ASGV), we previously identified a clone, pRM21, whose in vitro transcript (ASGV-RM21) does not induce any symptoms characteristic of the original (wild-type) cDNA clone (ASGV-wt) in several host plants. Interestingly, ASGV-RM21 has only a single, translationally silent nucleotide substitution, U to C, at nucleotide 4646 of the viral genome within open reading frame (ORF) 1. Here, we characterize and verify this unprecedented silent-mutation-induced attenuation of symptoms in infected plants. Northern and Western blot analyses showed that less ASGV-RM21 accumulates in host plants than ASGV-wt. In addition, two more silent substitutions, U to A and U to G, constructed by site-directed mutagenesis at the same nucleotide (4646), also induced attenuated symptoms. This is the first report that a single silent substitution attenuates virus-infection symptoms and implicates a novel determinant of disease symptom severity.