Coexpression of R2 and Os;cycH;1 in tobacco leaf sections. (A) Amplification of R2 and Os;cycH;1 cDNAs by RT-PCR. Transgenic seedlings were treated with (+) or without (-)1 μM DEX for 24 h, and 1 μg of total RNA was used for RT-PCR with specific primers for R2, Os;cycH;1, or 18S rRNA. The vector control line (Vec), the R2 transgenic line R1-1, and lines transformed with both R2 and Os;cycH;1 cDNAs, B1-1 (lane 1), B1-3 (lane 2), B1-9 (lane 3), and B1-12 (lane 4) are shown. (B) Enhancement of callus growth by coexpression of Os;cycH;1 with R2. Leaf discs (measuring 6 mm in diameter) carrying the empty vector (Vec), R2 cDNA (R1-1), or both R2 and Os;cycH;1 cDNAs (B1-3) were cultured for 4 weeks on media containing 2.0 μg/ml NAA with (open bars) or without (solid bars) 1 μM DEX, and their weight was measured. Data are mean ± SD of 18 samples.