CRISPR/Cas9-Mediated Multiplex Genome Editing of JAGGED Gene in Brassica napus L.

Abstract

Pod shattering resistance is an essential component to achieving a high yield, which is a substantial objective in polyploid rapeseed cultivation. Previous studies have suggested that the Arabidopsis JAGGED (JAG) gene is a key factor implicated in the regulatory web of dehiscence fruit. However, its role in controlling pod shattering resistance in oilseed rape is still unknown. In this study, multiplex genome editing was carried out by the CRISPR/Cas9 system on five homoeologs (BnJAG.A02, BnJAG.C02, BnJAG.C06, BnJAG.A07, and BnJAG.A08) of the JAG gene. Knockout mutagenesis of all homoeologs drastically affected the development of the lateral organs in organizing pod shape and size. The cylindrical body of the pod comprised a number of undifferentiated cells like a callus, without distinctive valves, replum, septum, and valve margins. Pseudoseeds were produced, which were divided into two halves with an incomplete layer of cells (probably septum) that separated the undifferentiated cells. These mutants were not capable of generating any productive seeds for further generations. However, one mutant line was identified in which only a BnJAG.A08-NUB-Like paralog of the JAG gene was mutated. Knockout mutagenesis in BnJAG.A08-NUB gene caused significant changes in the pod dehiscence zone. The replum region of the mutant was increased to a great extent, resulting in enlarged cell size, bumpy fruit, and reduced length compared with the wild type. A higher replum–valve joint area may have increased the resistance to pod shattering by ~2-fold in JAG mutants compared with wild type. Our results offer a basis for understanding variations in Brassica napus fruit by mutating JAG genes and providing a way forward for other Brassicaceae species.