The 3′-untranslated region of RNA1 as a primary determinant of temperature sensitivity of red clover necrotic mosaic virus Canadian strain

Abstract

Red clover necrotic mosaic virus Canadian strain (RCNMV-Can) induces symptoms on host plants at 17°C, but not at 25°C. We investigated the temperature sensitivity of RCNMV-Can in Nicotiana benthamiana plants and protoplasts using infectious transcripts of genomic RNAs 1 and 2. Viral RNAs accumulated in both inoculated and noninoculated leaves at 17°C, whereas no viral RNAs were detected at 25°C in either inoculated or noninoculated leaves. Similar temperature sensitivity in RNA accumulation was observed in protoplasts, and no viral RNAs were detected at temperatures above 22°C. These results indicate that the temperature sensitivity of RCNMV-Can occurs at an early stage of infection, including during RNA replication. Using reassortant viruses and chimeric RNAs 1 between RCNMV-Can and the RCNMV Australian strain, which accumulates viral RNAs at nonpermissive temperatures for RCNMV-Can, we demonstrated that a viral determinant for the temperature sensitivity resides in the 3′-untranslated region of RNA1. © 2002 Elsevier Science (USA).