Genome-Wide Identification of Binding Sites for NAC and Yabby Transcription Factors and Co-Regulated Genes by ChIP-Seq and RNA-Seq

Two plant-specific transcription factors, NAC and YABBY, are involved in important plant developmental processes. However their molecular mechanisms, especially DNA binding sites and co-regulated genes, are largely unknown during soybean seedling development. In order to identify genome-wide binding sites of specific members of the NAC and YABBY transcription factors and co-regulated genes, we performed Chromatin Immunoprecipitation Sequencing (ChIP-Seq) and RNA Sequencing (RNA-Seq) using cotyledons from soybean seedling developmental stages. Our RNA-Seq data revealed that these particular NAC and YABBY transcription factors showed a clear expression pattern during soybean seedling development. The highest level of their expression was found in seedling developmental stage 4 when cotyledons undergo a physiological transition from non-photosynthetic storage tissue to a metabolically active photosynthetic tissue.  Our ChIP-Seq data identified 72 genes potentially regulated by the NAC and 96 genes by the YABBY transcription factors examined. Our RNA-Seq data revealed highly differentially expressed candidate genes regulated by the NAC transcription factor include lipoxygense, pectin methyl esterase inhibitor, DEAD/DEAH box helicase and homeobox proteins. YABBY-regulated genes include AP2 transcription factor, fatty acid desaturase and WRKY transcription factor. Additionally, we have identified DNA binding motifs for the NAC and YABBY transcription factors. Genome-wide determination of binding sites for NAC and YABBY transcription factors and identification of candidate genes regulated by these transcription factors will advance the understanding of complex gene regulatory networks during soybean seedling development.  Our data imply that there is transcriptional reprogramming during the functional transition of cotyledons from non-photosynthetic storage tissue to metabolically active photosynthetic tissue.