PSTV INFECTION IN TOBACCO (NICOTIANA-TABACUM-L) TRANSFORMED WITH PSTVCDNA

Tobacco cv. White Burley was transformed with disarmed expression vect or pCB1314 containing dimeric cDNA of potato spindle tuber viroid (PST V, severe strain) in plus orientation regulated from the mannopine pro moter. Amount of PSTV specific (-) and (+) sequences and PSTV circular forms was measured in transformed tobacco stock and compared with PST V content in untransformed tomato and tobacco grafts. It follows from the results that lower rate of accumulation of PSTV in tobacco as comp ared with tomato is due to less intensive viroid transportation throug h the cytoplasm and/or cell to cell movement, whereas both, viroid rep lication and processing showed comparable characteristics in tomato an d tobacco with respect to accumulation of minus and plus strands and c ircular forms in infected tissues. Despite of accumulation of viroid i n comparable amount in both transformed tobacco and infected tomato, n o expression of any morphological symptom of disease was observed in t ransgenic tobacco.