MPMI Vol. 8, No. 6, 1995, pp. 979-987.

Open Reading Frames of Turnip Crinkle Virus Involved in Satellite Symptom Expression and Incompatibility with Arabidopsis thaliana Ecotype Dijon

Jong-Won Oh*, Qingzhong Kong#, Chuanzheng Song#, Clifford D. Carpenter#, and Anne E. Simon#

*Department of Microbiology, #Department of Biochemistry and Molecular Biology and Program in Molecular and Cellular Biology, University of Massachusetts, Amherst 01003, U.S.A.

Received 9 January 1995. Accepted 1 August 1995.

Carmoviruses are single-stranded, single component RNA viruses that include turnip crinkle virus (TCV) and the recently discovered cardamine chlorotic fleck virus (CCFV). Full-length, biologically active cDNAs were constructed for the TCV-M isolate and the Blue Lake isolate of CCFV. Using chimeric viruses constructed between isolates of TCV that produce mild or severe symptoms when coinoculated with a virulent satellite RNA, a Glu residue at position 1,144 in the polymerase open reading frame was identified as being involved in satellitemediated symptom expression. To analyze viral determinants involved in resistance, chimeric viruses with precisely exchanged open reading frames were produced between TCV, which does not infect the Arabidopsis thaliana ecotype Dijon (Di-0), and CCFV, which can infect Di-0. TCV with the coat protein of CCFV was able to systemically infect Di-0 although whole plant hybridizations revealed that the hybrid virus spread more slowly than either of the two parental viruses. These results indicate that the coat protein is an important viral determinant in the resistance of Di-0 to TCV.