Expression of Hop Stunt Viroid from Its cDNA in Transgenic Tobacco Plants: Identification of Tobacco as a Host Plant. Jun Yamaya. Plant Laboratory, Kirin Brewery Company, Kitsuregawa-machi, Shioya-gun, Tochigi 329-14, Japan.. Masaharu Yoshioka(1),Teruo Sano(2), Eishiro Shikata(2), and Yoshimi Okada(3). (1)Plant Laboratory, Kirin Brewery Company, Kitsuregawa-machi, Shioya-gun, Tochigi 329-14, Japan; (2)Department of Botany, Faculty of Agriculture, Hokkaido University, Sapporo 060, Japan; and (3)Department of Biophysics and Biochemistry, Faculty of Science, University of Tokyo, Hongo, Tokyo 113, Japan.. MPMI 2:169-174. Accepted 27 February 1989. Copyright 1989 The American Phytopathological Society.

Hop stunt viroid (HSV) cDNAs were introduced into tobacco plants by a Ti plasmid-mediated transformation. The replication of infectious HSV was detected in transgenic tobacco plants, carrying two tandemly repeated HSV cDNA sequences, and in their progeny as well. This is the first report of transgenic plants expressing viroids and offers a novel strategy for the study of viroid-host interactions. Previously, tobacco had been reported to be resistant to HSV infection. Accordingly, we examined the susceptibility of tobacco to HSV by two different methods, agroinfection and mechanical inoculation. Tobacco was readily agroinfected with HSV; however, tobacco was mechanically infected at a greatly reduced level of efficiency. These results identify Nicotiana tabacum as a host of HSV.