Department of Genetics, Cell Biology and Development, University of Minnesota, St. Paul, Minnesota 55108.
Pairwise, Durham, North Carolina 27709.
Plant Physiol. 2020 Aug;183(4):1453-1471. doi: 10.1104/pp.19.01194. Epub 2020 May 26.
Site-directed nucleases (SDNs) used for targeted genome editing are powerful new tools to introduce precise genetic changes into plants. Like traditional approaches, such as conventional crossing and induced mutagenesis, genome editing aims to improve crop yield and nutrition. Next-generation sequencing studies demonstrate that across their genomes, populations of crop species typically carry millions of single nucleotide polymorphisms and many copy number and structural variants. Spontaneous mutations occur at rates of ∼10 to 10 per site per generation, while variation induced by chemical treatment or ionizing radiation results in higher mutation rates. In the context of SDNs, an off-target change or edit is an unintended, nonspecific mutation occurring at a site with sequence similarity to the targeted edit region. SDN-mediated off-target changes can contribute to a small number of additional genetic variants compared to those that occur naturally in breeding populations or are introduced by induced-mutagenesis methods. Recent studies show that using computational algorithms to design genome editing reagents can mitigate off-target edits in plants. Finally, crops are subject to strong selection to eliminate off-type plants through well-established multigenerational breeding, selection, and commercial variety development practices. Within this context, off-target edits in crops present no new safety concerns compared to other breeding practices. The current generation of genome editing technologies is already proving useful to develop new plant varieties with consumer and farmer benefits. Genome editing will likely undergo improved editing specificity along with new developments in SDN delivery and increasing genomic characterization, further improving reagent design and application.
靶向基因组编辑用的位点特异性核酸酶（SDN）是将精确的遗传变化引入植物的强大新工具。与传统方法（如常规杂交和诱导诱变）一样，基因组编辑旨在提高作物产量和营养价值。新一代测序研究表明，在其基因组中，作物物种的群体通常携带数百万个单核苷酸多态性，以及许多拷贝数和结构变异。自发突变的发生率为每代每位点 10 到 10 个，而化学处理或电离辐射诱导的变异导致更高的突变率。在 SDN 的情况下，脱靶变化或编辑是指在与靶向编辑区域具有序列相似性的位点上发生的非预期的、非特异性突变。与在育种群体中自然发生的或通过诱导诱变方法引入的变异相比，SDN 介导的脱靶变化可导致少量额外的遗传变异。最近的研究表明，使用计算算法来设计基因组编辑试剂可以减轻植物中的脱靶编辑。最后，通过经过充分验证的多代育种、选择和商业品种开发实践，作物受到强烈选择，以消除非典型植物。在这种情况下，与其他育种实践相比，作物中的脱靶编辑不会带来新的安全问题。当前一代的基因组编辑技术已经在开发具有消费者和农民利益的新型植物品种方面证明是有用的。随着 SDN 传递和不断增加的基因组特征的新发展，基因组编辑可能会提高编辑特异性，进一步改进试剂设计和应用。
