Seed-specific repression of GUS activity in tobacco plants by antisense RNA

β-Conglycinin, the 7S storage protein of soybean, is expressed only in seeds and is regulated predominantly by gene transcription [5]. We applied an antisense strategy to modify expression of a β-glucuronidase (uidA or gusA) gene in seeds using a promoter from a β-conglycinin gene. Transgenic tobacco plants harboring the gusA gene under the control of the CaMV 35S promoter were retransformed with a gene construct comprising the β-conglycinin promoter fused to the gusA gene in the antisense orientation. Double transformants were regenerated and transformation was confirmed by Southern blot hybridization. Seed-specific repression of GUS activity was observed in lines containing high copy numbers of the antisense gusA transgene. Suppression of GUS activity was correlated with the amounts of (−) sense gusA transcript detected and concomitantly with a decrease in gusA transcript levels. Furthermore, the amount of suppression of GUS activity was greatest during mid to late stages of seed development, when expression of the α′ promoter is high. These results indicate that suppression of GUS activity is due to expression of the antisense gene.