Expression pattern of RBBI genes during germination. A, Northern-blot analysis of RBBI genes. Accumulation of the RBBI mRNAs was detected 24, 48, and 72 h after the onset of seed imbibition. In situ hybridization results showing RBBI gene expression in scutellar epithelium (SE; B), aleurone layer (AL; C), and young embryo (EM; D) of imbibed germinating rice seeds. The conserved coding region of the RBBI2-3 gene (450 bp) was used as the probe.