The sense and antisense coat protein gene of alfalfa mosaic virus strain N20 confers protection in transgenic tobacco plants

The coat protein gene of a South Australian strain of alfalfa mosaic virus (AMV-N20 (NcS)) has been cloned, sequenced, and transferred into Nicotiana tabacum L. cv. Xanthi via Agrobacterium tumefaciens under the control of the CaMV 35S promoter. A number of lines (T0 generation) were selected with the coat protein gene either in sense orientation (CP+) or in antisense orientation (CPi). The T0 plants were tested for their gene expression and susceptibility to the homologous AMV strain. A signiflcant delay in the onset of symptoms and a reduction in virus accumulation was observed in CP+ plants mechanically inoculated with AMV. CPi plants were also signiflcantly protected but less so than the CP+ plants. Plants transformed with the expression vector only (CP0) showed a minor resistance to local infection on inoculated leaves compared with untransformed plants. The strategy of coat protein mediated protection (CPMP) using the CP gene in either messenger sense or antisense would therefore be appropriate for testing on economically important pasture legumes.