The effect of helper component on the uptake and localization of potyviruses in Myzus persicae

125I-labeled virions were used to determine whether helper component (HC) affected the uptake or distribution of potyviruses in aphids. Aphids were allowed to acquire purified, 125I-labeled tobacco etch virus or potato virus Y mixed with HC or with inactivated HC. Helper component had no effect upon uptake of labeled virus, as measured by gamma counting. Autoradiography of freeze-sectioned aphids revealed, however, that in the presence of HC, label was associated with the maxillary stylets and with portions of the alimentary canal anterior to the gut, as well as with the gut region. Label accumulated only in the gut in control aphids. This selective localization of virus acquired in the presence of HC supports a binding mechanism for the mode of action of HC.