MOVEMENT OF TOMATO YELLOW LEAF CURL GEMINIVIRUS (TYLCV) - INVOLVEMENTOF THE PROTEIN ENCODED BY ORF C4

Tomato yellow leaf curl virus (TYLCV) is a whitefly-transmitted gemini virus with a monopartite genome. We have investigated the ability of a TYLCV DNA mutant containing a disrupted ORF C4 to infect Nicotiana be nthamiana and tomato plants. The mutant retained the capability of aut onomous replication in protoplast-derived cells of tomato and was able to infect N. benthamiana plants systemically although DNA levels were reduced and symptom development was attenuated. However, when tomato plants were inoculated, the virus was unable to move systemically unle ss a second site mutation or a reversion in planta restored the integr ity of ORF C4. The infected plants remained asymptomatic or showed ver y mild symptoms. The results strongly suggest that the ORF C4 encodes a protein involved in virus movement, a novel finding for whitefly-tra nsmitted geminiviruses. The involvement of a C4 protein in symptom det ermination is discussed, (C) 1994 Academic Press, Inc.