Revolutionizing Classical Breeding in Agriculture through Genome Editing.

Historically, plant breeders have relied on natural variation and selection processes to develop traits critical for increased productivity in agronomically important food and feed crops. The ability to induce genetic variation and develop new traits by simple, inexpensive, fast, and precise methods to direct the modification of endogenous genes has been viewed as the next breakthrough. The rate-limiting step in genome editing has been the ability to produce and precisely direct DNA double-strand breaks (DSBs) to the targeted genomic location. With the introduction of protein-based DSB reagents like zinc-finger nucleases, meganucleases and TALENs, plant biotechnology began to take steps towards realizing a revolutionary change in agriculture. Most recently, a DSB system of bacterial origin known as CRISPR (Clustered Regularly Interspersed Short Palindromic Repeats) has been discovered in which CRISPR associated components (Cas) provide natural immunity against invading foreign DNA. Using the Cas9-guideRNA component of this system, a programmable RNA-guided endonuclease system has been developed to become a simple, inexpensive and versatile platform for genome editing in eukaryotic organisms, including plants. Cas9-guideRNA gene editing can achieve changes in the targeted native genes without the introduction of the foreign DNA material into the final organism. Therefore, this outcome parallels classical mutagenesis-based breeding, although achieved with much higher efficiency and precision.  Adoption of robust genome modification methods to induce genetic variation will accelerate the continued development of modern breeding techniques to address challenges of a growing population.  The Genome Modification Group at DuPont Pioneer uses a variety of DSB approaches in its research programs to modify the corn, rice, sorghum and soybean genomes for the purpose of gene editing and gene stacking.  Examples of gene editing and gene insertion and their application to accelerate crop improvement will be presented.