Abstract
We produced dwarf torenia plants by genetic engineering using a gibberellin (GA) 20-oxidase gene from pumpkin immature seeds. A strong promoter cassette (El2-Ω) was used to enhance the 20-oxidase expression in transgenic plants. We selected 2 lines of transformants (#1-1 and 1-6) showing a dwarf-phenotype compared with wild-type plants. In the T2 generations of each line, the transgene was integrated as 2 copies in #1-1 line and as a single copy in #1-6 line. The transcripts for the transgene were detected only in dwarfs of both lines. The endogenous levels of biologically active GA1 and its precursors were reduced, whereas large amounts of GA17, which are inactive products of the pumpkin GA 20-oxidase, accumulated in the dwarfs. These results indicate that over-expression of the pumpkin GA 20-oxidase results in a diversion of the GA biosynthetic pathway to inactive products and this technique may be useful for producing dwarf plants.
