Function Analysis of the PR55/B Gene Related to Self-Incompatibility in Chinese Cabbage Using CRISPR/Cas9.

Chinese cabbage, a major crop in Korea, shows self-incompatibility (SI). SI is controlled by the type 2A serine/threonine protein phosphatases (PP2As). The PP2A gene is controlled by regulatory subunits that comprise a 36 kDa catalyst C subunit, a 65 kDa regulatory A subunit, and a variety of regulatory B subunits (50-70 kDa). Among them, the PP2A 55 kDa B regulatory subunit (PR55/B) gene located in the A05 chromosome has 13 exons spanning 2.9 kb, and two homologous genes, Bra018924 and Bra014296, were found to be present on the A06 and A08 chromosome, respectively. In this study, we performed a functional analysis of the PR55/B gene using clustered regularly interspaced short palindromic repeats/CRISPR-associated system 9 (CRISPR/Cas9)-mediated gene mutagenesis. CRISPR/Cas9 technology can be used to easily introduce mutations in the target gene. Tentative gene-edited lines were generated by the Agrobacterium-mediated transfer and were selected by PCR and Southern hybridization analysis. Furthermore, pods were confirmed to be formed in flower pollination (FP) as well as bud pollination (BP) in some gene-edited lines. Seed fertility of gene-edited lines indicated that the PR55/B gene plays a key role in SI. Finally, self-compatible T-DNA-free T2 gene-edited plants and edited sequences of target genes were secured. The self-compatible Chinese cabbage developed in this study is expected to contribute to Chinese cabbage breeding.