Estimation of transcript levels of the tomato (S. peruvianum) BRI1 transgene in tobacco plants. Top, The phenotypical difference between wild-type and tobacco plants containing the 35S∷SpSR160 construct when grown in vitro. Bottom, Semiquantitative reverse transcription-PCR was performed to estimate the transcript levels of SpBRI1 in wild-type tobacco plants, and tobacco plants transformed with SpBRI1 (35S∷SpSR160; generated and provided by J. Scheer and C. A. Ryan; two individual plants). For comparison, SpBRI1 levels were estimated in S. peruvianum suspension-cultured cells. Primers specifically amplified SpBRI1, but not NtBRI1. ACTIN transcript levels are shown as a loading control. Molecular weight marker (1-kb ladder, New England Biolabs: only the markers from 0.5 til 5.0 kb are visible) is shown in the first lanes of each gel. Samples were taken after 22, 24, 26, 28, 30, 32, and 34 cycles.