Development of an efficient chromatin immunoprecipitation method to investigate protein-DNA interaction in oleaginous castor bean seeds.

Chromatin immunoprecipitation (ChIP) is usually a reliable technique to find the binding sites of a transcription factor. In the current study, we developed a suitable ChIP method using developing castor bean seeds. A castor bean seed with large and persistent endosperm contains high amounts of storage lipids (ca. 50-60%) and is often considered as a model material to studying seed biology. In oleaginous seeds, due to the rich oils which could seriously affect immunoprecipitation and DNA isolation, it is often difficult to carry out a successful ChIP experiment. Thus, the development of an efficient ChIP method for oleaginous seeds is required. In this study, we modified different steps, including tissue preparation for cross-linking, chromatin washing, sonication and immunoprecipitation of other existing methods. As exemplified by the targeted gene identification of a master regulator WRI1, which regulates fatty acid biosynthesis, we found that the improved ChIP method worked well. We analyzed percentage input and fold changes of the ChIPed DNA. We also made successful ChIP-seq libraries using this method. This method provides a technical support not only for use on castor bean seeds; it might be used equally to analyze protein-DNA interaction in vivo in other oleaginous seeds.