International Journal of Molecular Sciences Article Comprehensive Analysis of CRISPR/Cas9-Mediated Mutagenesis in Arabidopsis thaliana by Genome-Wide Sequencing Wenjie Xu 1,2 , Wei Fu 2, Pengyu Zhu 2, Zhihong Li 1, Chenguang Wang 2, Chaonan Wang 1,2, Yongjiang Zhang 2 and Shuifang Zhu 1,2,* 1 College of Plant Protection, China Agricultural University, Beijing 100193 China 2 Institute of Plant Quarantine, Chinese Academy of Inspection and Quarantine, Beijing 100176, China * Correspondence:
[email protected] Received: 9 July 2019; Accepted: 21 August 2019; Published: 23 August 2019 Abstract: The clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein (Cas) system has been widely applied in functional genomics research and plant breeding. In contrast to the off-target studies of mammalian cells, there is little evidence for the common occurrence of off-target sites in plants and a great need exists for accurate detection of editing sites. Here, we summarized the precision of CRISPR/Cas9-mediated mutations for 281 targets and found that there is a preference for single nucleotide deletions/insertions and longer deletions starting from 40 nt upstream or ending at 30 nt downstream of the cleavage site, which suggested the candidate sequences for editing sites detection by whole-genome sequencing (WGS). We analyzed the on-/off-target sites of 6 CRISPR/Cas9-mediated Arabidopsis plants by the optimized method. The results showed that the on-target editing frequency ranged from 38.1% to 100%, and one off target at a frequency of 9.8%–97.3% cannot be prevented by increasing the specificity or reducing the expression level of the Cas9 enzyme.