Summary: Recently, CRISPR‐Cas (clustered, regularly interspaced short palindromic repeats–CRISPR‐associated proteins) system has been used to produce plants resistant to DNA virus infections. However, there is no RNA virus control method in plants that uses CRISPR‐Cas system to target the viral genome directly. Here, we reprogrammed the CRISPR‐Cas9 system from Francisella novicida to confer molecular immunity against RNA viruses in Nicotiana benthamiana and Arabidopsis plants. Plants expressing FnCas9 and sgRNA specific for the cucumber mosaic virus (CMV) or tobacco mosaic virus (TMV) exhibited significantly attenuated virus infection symptoms and reduced viral RNA accumulation. Furthermore, in the transgenic virus‐targeting plants, the resistance was inheritable and the progenies showed significantly less virus accumulation. These data reveal that the CRISPR/Cas9 system can be used to produce plant that stable resistant to RNA viruses, thereby broadening the use of such technology for virus control in agricultural field.

Despite early domestication around 3000 BC, the evolutionary history of the ancient allotetraploid speciesBrassica juncea(L.) Czern & Coss remains uncertain. Here, we report a chromosome-scale de novo assembly of a yellow-seededB. junceagenome by integrating long-read and short-read sequencing, optical mapping and Hi-C technologies. Nuclear and organelle phylogenies of 480 accessions worldwide supported thatB. junceais most likely a single origin in West Asia, 8,000–14,000 years ago, via natural interspecific hybridization. Subsequently, new crop types evolved through spontaneous gene mutations and introgressions along three independent routes of eastward expansion. Selective sweeps, genome-wide trait associations and tissue-specific RNA-sequencing analysis shed light on the domestication history of flowering time and seed weight, and on human selection for morphological diversification in this versatile species. Our data provide a comprehensive insight into the origin and domestication and a foundation for genomics-based breeding ofB. juncea.

Besides its powerful capability for genome editing, the clustered, regularly interspaced short palindromic repeats (CRISPR)/CRISPR‐associated (Cas) (CRISPR/Cas) systems, has been exploited to combat virus infection in eukaryotic organisms (Zaidi et al., 2016). By harnessing CRISPR/Cas system, its compelling inhibiting activities against DNA viruses (Ali et al., 2015; Baltes et al., 2015; Ji et al., 2015) or RNA viruses (Aman et al., 2018; Zhang et al., 2018) were reported in many cases. Moreover, due to the facts that the eukaryotic viruses themselves do not equip the ability to counter this prokaryotic immune defense, by utilization of such strategy, we could establish effective control and eradiation strategy against the eukaryotic virus.

Brassica napus, an allotetraploid crop, is hypothesized to be a hybrid from unknown varieties of Brassica rapa and Brassica oleracea. Despite the economic importance of B. napus, much is unresolved regarding its phylogenomic relationships, genetic structure, and diversification. Here we conduct a comprehensive study among diverse accessions from 183 B. napus (including rapeseed, rutabaga, and Siberian kale), 112 B. rapa, and 62 B. oleracea and its wild relatives. Using RNA-seq of B. napus accessions, we define the genetic diversity and sub-genome variance of six genetic clusters. Nuclear and organellar phylogenies for B. napus and its progenitors reveal varying patterns of inheritance and post-formation introgression. We discern regions with signatures of selective sweeps and detect 8,187 differentially expressed genes with implications for B. napus diversification. This study highlights the complex origin and evolution of B. napus providing insights that can further facilitate B. napus breeding and germplasm preservation.