Preliminary Studies on the Intergeneric Hybridization Between Brassica napus with OguCMS and Orychophragmus violaceus

In the cross between B. napus with OguCMSOrychophragmus violaceus, pre-fertilizatiocompatibility was observed. An intergeneric hybrid was successfully obtained by usinovary culture. The hybrid status was confirmed by cytology, morphology, fertilityisozyme and miosis analysis. The seed setting rate was 0.0072%. An amphidiploid of thhybrid was also produced by the use of chromosome-doubling method with 0.1% colchicinetreatment. Obtaining this hybrid and its amphidiploid has important theoretical anutilization value.

Genome assembly of the Brassicaceae diploid Orychophragmus violaceus reveals complex whole-genome duplication and evolution of dihydroxy fatty acid metabolism

Orychophragmus violaceus is a Brassicaceae species widely cultivated in China,particularly as a winter cover crop in northern China because of its low-temperature tolerance and low water demand.Recently,O.violaceus has also been cultivated as a potential industrial oilseed crop because of its abundant 24-carbon dihydroxy fatty acids(diOH-FAs),which contribute to superior high-temperature lubricant properties.In this study,we performed de novo assembly of the O.violaceus genome.Whole-genome synteny analysis of the genomes of its relatives demonstrated that O.violaceus is a diploid that has undergone an extrawhole-genome duplication(WGD)after the Brassicaceae-specific a-WGD event,with a basic chromosome number of x=12.Formation of diOH-FAs is hypothesized to have occurred after the WGD event.Based on the genome and the transcriptome data from multiple stages of seed development,we predicted that OvDGAT1-1 and OvDGAT1-2 are candidate genes for the regulation of diOH-FA storage in O.violaceus seeds.These results may greatly facilitate the development of heat-tolerant and eco-friendly plant-based lubricants using O.violaceus seed oil and improve our understanding of the genomic evolution of Brassicaceae.

The genome of Orychophragmus violaceus provides genomic insights into the evolution of Brassicaceaepolyploidizationandits distinct traits

Orychophragmus violaceus,referred to as‘‘eryuelan’’(February orchid)in China,is an early-flowering ornamental plant.The high oil content and abundance of unsaturated fatty acids in O.violaceus seeds make it a potential high-quality oilseed crop.Here,we generated a whole-genome assembly for O.violaceus using Nanopore and Hi-C sequencing technologies.The assembled genome of O.violaceus was~1.3 Gb in size,with 12 pairs of chromosomes.Through investigation of ancestral genome evolution,we determined that the genome of O.violaceus experienced a tetraploidization event from a diploid progenitor with the translocated proto-Calepineae karyotype.Comparisons between the reconstructed subgenomes of O.violaceus identified indicators of subgenome dominance,indicating that subgenomes likely originated via allotetraploidy.O.violaceus was phylogenetically close to the Brassica genus,and tetraploidy in O.violaceus occurred approximately 8.57 million years ago,close in time to the whole-genome triplication of Brassica that likely arose via an intermediate tetraploid lineage.However,the tetraploidization in Orychophragmus was independent of the hexaploidization in Brassica,as evidenced by the results from detailed phylogenetic analyses and comparisons of the break and fusion points of ancestral genomic blocks.Moreover,identification of multi-copy genes regulating the production of high-quality oil highlighted the contributions of both tetraploidization and tandem duplication to functional innovation in O.violaceus.These findings provide novel insights into the polyploidization evolution of plant species and will promote both functional genomic studies and domestication/breeding efforts in O.violaceus.