Characterization of petunia BPBT gene expression. A, Tissue specificity of BPBT mRNA. RNA gel blot of total RNA (5 μg per lane) isolated from young leaves, sepals, tubes, and limbs of corollas, pistil, stamens, and ovaries of 2-d-old petunia flowers. The top gel represents the results of hybridization with a coding region of the BPBT genes as a probe. Autoradiography was performed overnight. The blot shown here as well as in B and C were rehybridized with an 18S rDNA probe (bottom) to standardize samples. B, Developmental changes in steady-state BPBT mRNA level in limbs of petunia corollas. Total RNA was isolated at different stages of flower development, from mature buds to day 7 postanthesis. Each lane contained 5 μg of total RNA. Autoradiography was performed overnight. C, RNA gel-blot analysis of steady-state BPBT mRNA levels in petunia flowers during a normal light/dark cycle. Total RNA was isolated from limbs of 2- and 3-d-old flowers at time points indicated at top of figure, and 5 μg of total RNA was loaded in each lane. Autoradiography was performed overnight.