Figure 7.

A, Transcript levels of StSUT4, the GA biosynthetic enzyme GA20ox1, and the ethylene biosynthetic enzyme StACO3 in StSUT4-RNAi plants as determined by quantitative real-time PCR. A, StSUT4 expression in potato leaves treated with phytohormones and phytohormone inhibitors paclobutrazol (inhibitor of GA biosynthesis) and silver nitrate (inhibitor of the ethylene receptor). StSUT4 expression is inducible by GA₃ at the end of the light period and by ethephon treatment over the whole light period. Potato wild-type plants were treated with 20 μm GA₃, 350 μm paclobutrazol, 350 μm ethephon, or 1 mm silver nitrate, and StSUT4 mRNA was determined by real-time PCR analysis relative to the level of ubiquitin transcripts. B, Quantification of transcripts of the GA biosynthetic enzyme GA20ox1 in wild-type and StSUT4-RNAi plants showing reduced levels of GA20ox1 in source leaves of StSUT4-RNAi plants at the end of the light period if compared to wild-type levels. C, Quantification of the transcripts of the ethylene biosynthetic enzyme StACO3 in wild-type and StSUT4-RNAi plants showing significantly reduced levels of StACO3 mRNA levels in StSUT4-RNAi plants at any time. Ubiquitin transcript levels were used as internal standard for relative quantification in all experiments. Experiments were performed with greenhouse plants grown under LD conditions. sd is given.