Rice protein-binding microarrays: a tool to detect cis-acting elements near promoter regions in rice.

The present study showed that a rice (Oryza sativa)-specific protein-binding microarray (RPBM) can be applied to analyze DNA-binding motifs with a TF where binding is evaluated in extended natural promoter regions. The analysis may facilitate identifying TFs and their downstream genes and constructing gene networks through cis-elements. Transcription factors (TFs) regulate gene expression at the transcriptional level by binding a specific DNA sequence. Thus, predicting the DNA-binding motifs of TFs is one of the most important areas in the functional analysis of TFs in the postgenomic era. Although many methods have been developed to address this challenge, many TFs still have unknown DNA-binding motifs. In this study, we designed RPBM with 40-bp probes and 20-bp of overlap, yielding 49 probes spanning the 1-kb upstream region before the translation start site of each gene in the entire genome. To confirm the efficiency of RPBM technology, we selected two previously studied TFs, OsWOX13 and OsSMF1, and an uncharacterized TF, OsWRKY34. We identified the ATTGATTG and CCACGTCA DNA-binding sequences of OsWOX13 and OsSMF1, respectively. In total, 635 and 932 putative feature genes were identified for OsWOX13 and OsSMF1, respectively. We discovered the CGTTGACTTT DNA-binding sequence and 195 putative feature genes of OsWRKY34. RPBM could be applicable in the analysis of DNA-binding motifs for TFs where binding is evaluated in the promoter and 5' upstream CDS regions. The analysis may facilitate identifying TFs and their downstream genes and constructing gene networks through cis-elements.