A modular toolbox for gRNA–Cas9 genome engineering in plants based on the GoldenBraid standard

Marta Vazquez-Vilar, Joan Miquel Bernabé-Orts, Asun Fernandez-del-Carmen, Pello Ziarsolo, Jose Blanca, Antonio Granell, Diego Orzaez

The efficiency, versatility and multiplexing capacity of RNA-guided genome engineering using the CRISPR/Cas9 technology enables a variety of applications in plants, ranging from gene editing to the construction of transcriptional gene circuits, many of which depend on the technical ability to compose and transfer complex synthetic instructions into the plant cell. The engineering principles of standardization and modularity applied to DNA cloning are impacting plant genetic engineering, by increasing multigene assembly efficiency and by fostering the exchange of well-defined physical DNA parts with precise functional information. Here we describe the adaptation of the RNA-guided Cas9 system to GoldenBraid (GB), a modular DNA construction framework being increasingly used in Plant Synthetic Biology. In this work, the genetic elements required for CRISPRs-based editing and transcriptional regulation were adapted to GB, and a workflow for gRNAs construction was designed and optimized. New software tools specific for CRISPRs assembly were created and incorporated to the public GB resources site. The functionality and the efficiency of gRNA-Cas9 GB tools were demonstrated in Nicotiana benthamiana using transient expression assays both for gene targeted mutations and for transcriptional regulation. The availability of gRNA-Cas9 GB toolbox will facilitate the application of CRISPR/Cas9 technology to plant genome engineering.