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標題: A single amino acid substitution in the movement protein enables the mechanical transmission of a geminivirus
作者: Chia-Hwa Lee 
You-Xiu Zheng 
Chin-Hsiang Chan 
Hsin-Mei Ku 
Chung-Jan Chang 
Fuh-Jyh Jan 
關鍵字: begomovirus;mechanical transmissibility;movement protein;ToLCNDV oriental melon isolate;tomato leaf curl New Delhi virus
Begomoviruses of the Geminiviridae are usually transmitted by whiteflies and rarely
by mechanical inoculation. We used tomato leaf curl New Delhi virus (ToLCNDV), a
bipartite begomovirus, to address this issue. Most ToLCNDV isolates are not mechanically
transmissible to their natural hosts. The ToLCNDV-OM isolate, originally identified
from a diseased oriental melon plant, is mechanically transmissible, while the
ToLCNDV-CB isolate, from a diseased cucumber plant, is not. Genetic swapping and
pathological tests were performed to identify the molecular determinants involved in
mechanical transmission. Various viral infectious clones were constructed and successfully
introduced into Nicotiana benthamiana, oriental melon, and cucumber plants
by Agrobacterium-mediated inoculation. Mechanical transmissibility was assessed via
direct rub inoculation with sap prepared from infected N. benthamiana. The presence
or absence of viral DNA in plants was validated by PCR, Southern blotting, and in situ
hybridization. The results reveal that mechanical transmissibility is associated with the
movement protein (MP) of viral DNA-B in ToLCNDV-OM. However, the nuclear shuttle
protein of DNA-B plays no role in mechanical transmission. Analyses of infectious
clones carrying a single amino acid substitution reveal that the glutamate at amino
acid position 19 of MP in ToLCNDV-OM is critical for mechanical transmissibility. The
substitution of glutamate with glycine at this position in the MP of ToLCNDV-OM
abolishes mechanical transmissibility. In contrast, the substitution of glycine with glutamate
at the 19th amino acid position in the MP of ToLCNDV-CB enables mechanical
transmission. This is the first time that a specific geminiviral movement protein has
been identified as a determinant of mechanical transmissibility.
Appears in Collections:植物病理學系

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