Identification of BD PROs from the MA and RS data sets. Embryos were isolated from 20 DAP immature maize kernels. Each construct was introduced twice using a particle gun with six embryos per bombardment. A: Promoters cloned based on the microarray data set (MA); B: Promoters cloned based on the RNA-seq data set (RS). Putative BD PROs that showed promoter activity in both directions are indicated by a red box. The remaining putative BD PROs showed either promoter activity in one direction or no promoter activity.