Expression of Cauliflower Mosaic Virus (CaMV) Gene VI in Transgenic Nicotiana bigelovii Complements a Strain of CaMV Defective in Long-Distance Movement in Nontransformed N. bigelovii. James E. Schoelz. Department of Plant Pathology, University of Missouri, Columbia 65211. Karen-Beth Goldberg(2), and Jennifer Kiernan(2). (1)Department of Plant Pathology, University of Missouri, Columbia 65211, and (2)Department of Plant Pathology, University of Kentucky, Lexington 40546 U.S.A. MPMI 4:350-355. Accepted 11 March 1991. Copyright 1991 The American Phytopathological Society.

Transgenic Nicotiana bigelovii var. multivalvus plants that express the gene VI-encoded product of strain D4 of cauliflower mosaic virus (CaMV) allow long-distance transport of CaMV strain H31, a virus that is unable to move systemically in non-transformed N. bigelovii. Previous work showed that the gene VI-encoded product of strain D4 determines the ability of recombinant viruses to infect N. bigelovii systemically. To test whether long-distance spread of H31 resulted from complementation or recombination with the “trans-gene,” transformed and normal N. bigelovii plants were inoculated with CaMV strain H31 recovered from noninoculated leaves of transgenic plants. Transgenic N. bigelovii developed systemic symptoms 3 to 4 wk after inoculation with passaged CaMV strain H31, while the non-transformed N. bigelovii remained symptomless. These experiments show that complementation by gene VI of D4 in the transgenic plant conferred on H31 the ability to move systemically in plants that do not normally allow systemic infection by this strain of CaMV.