To understand the genetic mechanisms involved in the functional transition of cotyledons from non-photosynthetic storage tissue to metabolically active photosynthetic tissue during soybean seedling development, we constructed seven different RNA-Seq libraries using cotyledons from each developmental stage separately. Analysis of RNA-Seq data from different developmental stages revealed the differential expression of many genes including transcription factors. In this study, we focused on NAC and YABBY transcription factors which showed a conspicuous expression pattern during soybean seedling development. Their expression gradually increases from stage 1 to stage 4 of soybean germinating cotyledons. The highest level of expression was found at stage 4. Then it gradually decreased as the germinating cotyledons develop a mature seedling. We investigated the differential expression of NAC and YABBY regulated genes between stage 3 (before the functional transition) and stage 6 (after the functional transition) using our RNA-Seq data. Based on our RNA-Seq data, we found that 10 genes are up-regulated and 21 genes are down-regulated by NAC transcription factor. Similarly we found that 19 genes are up-regulated and 27 genes are down-regulated by YABBY transcription factor. Overall design: High-throughput sequencing using Illumina HiSeq 2000 (RNA-Seq) was performed on seven developmental stages of soybean seedlings, with two biological replicates per stage.