Stable and heritable inhibition of the expression of nopaline synthase in tobacco expressing antisense RNA.

Antisense nopaline synthase (nos) (D-nopaline synthase; EC 1.5.1.19) RNA is stably expressed from the cauliflower mosaic virus 35S promoter in transformed tobacco plants. The expression of a previously introduced wild-type nos gene is inhibited by the antisense RNA, with less nos enzyme activity detected (by a factor of 8-50) depending on the tissue analyzed. The steady-state levels of nos mRNA are reduced in the presence of the antisense RNA, implying that mRNA degradation is probably the main mode of action for the decrease in expression in this system. The antisense RNA-expressing gene and its inhibition of nos expression are shown to be heritable, demonstrating that it is a potentially useful method for the modification of phenotype.