RESISTANCE RESPONSES OF PLANTS TO VIRUS INFECTIONS

Authors:	G. Loebenstein, A. Gera
Abstract: Non-host resistance, active responses and possibilities of obtaining transgenic resistant plants are discussed. The association of an inhibitor of virus replication (IVR) with the local lesion response may serve as a marker for such a resistance gene. IVR was found to be released from tobacco mosaic virus (TMV)-infected protoplasts of Samsun NN, a tobacco cultivar in which infection by TMV causes local lesions. IVR was not released from TMV-infected protoplasts of Samsun, which responds systemically to TMV. The biological activity was associated with two fractions with molecular weights of approximately 26,000 and 57,000, as determined by gel filtration. Antisera prepared against the two fractions were highly cross reactive, indicating that the 57,000 fraction is a dimer of the 26,000 fraction. IVR has a proteinaceous nature and its induction is sensitive to actinomycin D. A specific band (around 23K) was regularly observed in polyacrylamide gel electrophoresis (PAGE) of IVR. IVR was also obtained directly from TMV-infected tobacco NN leaves and from non-infected induced-resistant tissue.
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