OPEN READING FRAMES OF TURNIP CRINKLE VIRUS INVOLVED IN SATELLITE SYMPTOM EXPRESSION AND INCOMPATIBILITY WITH ARABIDOPSIS-THALIANA ECOTYPE DIJON

Carmoviruses are single-stranded, single component RNA viruses that in clude 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 CC FV. Using chimeric viruses constructed between isolates of TCV that pr oduce mild or severe symptoms when coinoculated with a virulent satell ite RNA, a Glu residue at position 1,144 in the polymerase open readin g frame was identified as being involved in satellite-mediated symptom expression, To analyze viral determinants involved in resistance, chi meric viruses with precisely exchanged open reading frames were produc ed between TCV, which does not infect the Arabidopsis thaliana ecotype Dijon (Di-0), and CCFV, which can infect Di-0, TCV with the coat prot ein 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 co at protein is an important viral determinant in the resistance of Di-0 to TCV.