Activation of a plant virus by related incomplete nucleoprotein particles

Abstract

In tests with bean pod mottle virus and cowpea yellow mosaic virus, the addition of noninfectious middle component of either virus to the corresponding bottom component resulted in an increase in infectivity of the latter. Top component, which contains no RNA, had no effect. Unrelated nucleoproteins or the middle component of related strains did not cause activation, which only occurred in homologous systems. The activating ability of middle component was sentitive to ultraviolet irradiation. Heated bottom component particles were reclaimable in terms of lesion formation when mixed with middle component particles. The data suggest that RNA in part of bottom component populations had been rendered noninfectious in such a way as to allow middle component to cause activation.