Arg-16 and Arg-21 in the N-terminal region of the triple-gene-block protein 1 of Bamboo mosaic virus are essential for virus movement.
The protein encoded by the first gene of the triple gene block (TGBp1) of potexviruses is required for movement of the viruses. It has been reported that single Arg-->Ala substitutions at position 11, 16 or 21 of TGBp1 of Bamboo mosaic virus (BaMV) eliminate its RNA-binding activity, while substitutions at position 16 or 21 only affect its NTPase activity (Liou et al., Virology 277, 336-344, 2000). However, it remains unclear whether these Arg-->Ala substitutions also affect the movement of BaMV in plants. To address this question, six mutants of BaMV, each containing either a single- or a double-alanine substitution at Arg-11, Arg-16 and Arg-21 of TGBp1, were constructed and used to infect Chenopodium quinoa and Nicotiana benthamiana. We found that all of the BaMV mutants were able to replicate in protoplasts of N. benthamiana. However, only the mutant with an Arg-11-->Ala substitution in TGBp1 remained capable of movement from cell to cell in plants. Mutants with Arg-16, Arg-21 or both Arg-16 and Arg-21 of TGBp1 replaced with alanine were defective in virus movement. This defect was suppressed when a wild-type TGBp1 allele was co-introduced into the cells using a novel satellite replicon. The ability to trans-complement the movement defect by the wild-type TGBp1 strongly suggests that the Arg-->Ala substitution at position 16 or 21 of TGBp1, which diminishes the RNA-binding and NTPase activities of TGBp1, also eliminates the capability of BaMV to move from cell to cell in host plants.
Lin
Ming-Kuem
MK
Graduate Institute of Biotechnology, National Chung Hsing University, Taichung 402, Taiwan.
Chang
Ban-Yang
BY
Graduate Institute of Biochemistry, National Chung Hsing University, Taichung 402, Taiwan.
Liao
Jia-Teh
JT
Graduate Institute of Biotechnology, National Chung Hsing University, Taichung 402, Taiwan.
Lin
Na-Sheng
NS
Institute of Botany, Academia Sinica, Taipei 115, Taiwan.
Hsu
Yau-Heiu
YH
Graduate Institute of Biotechnology, National Chung Hsing University, Taichung 402, Taiwan.
D000409:Alanine / Q000737:chemistry; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D001120:Arginine / Q000737:chemistry*; D027465:Chenopodium quinoa / Q000821:virology; D008969:Molecular Sequence Data; D018515:Plant Leaves / Q000821:virology; D053830:Plant Viral Movement Proteins; D017863:Potexvirus / Q000235:genetics / Q000502:physiology*; D031787:Sasa / Q000821:virology*; D014026:Nicotiana / Q000821:virology; D014764:Viral Proteins / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism
D053830:Plant Viral Movement Proteins; D014764:Viral Proteins; D001120:Arginine; D000409:Alanine