Genome Assembly Of Orychophragmus Limprichtianus And Hydroxy Fatty Acid Synthesis Related Genes Evolution Analysis

The seed oil of Orychophragmus violaceus（Chinese violet cress）is enriched in two novel C24 dihydroxy fatty acids(nebraskanic acid,7,18-OH-24:1^Δ15;wuhanic acid,7,18-OH-24:2^Δ15,21)that confer superior high-temperature lubrication properties to the oil.To better understand the biosynthesis of these fatty acids,we exploited the availability of Orychophragmus limprichtianus,a close relative of O.violaceus that is native to the Yellow Mountain region of China.In this study,we assembled the genome of O.limprichtianus,analyzed its evolutionary process,compared the differentially expressed genes in the seeds at the middle and late stages of development silique,and conducted phylogenetic analysis of dihydroxy fatty acid metabolism candidate genes,Finally,we obtained the following results:1.O.limprichtianus genome size was about 585Mb,with 69%repeat sequences and 0.96%heterozygosity.As the karyotype of each chromosomes pairs in the genome of O.limprichtianus is still highly consistent at the genome level,we considered it to be an allienated autotetraploid,and divided it into two subgroups（subgroup A:Chr01 to Chr07,subgroup B:Chr08 to Chr14）.2.The results of ancestral karyotype construction showed that the karyotypes of the two subgroups were basically the same as those of the Brassica ancestors.These results indicated that the genome of O.limprichtianus did not undergo large-scale fracture and recombination after the whole genome duplication,while gradually alienated and tended to be stable.3.The results of differential gene expression enrichment analysis showed that there were three different copies of FAE1 gene（Ol FAE1-1,Ol FAE1-2 and Ol FAE1-3）and three different copies of FAD2 gene（Ol FAD2-1,Ol FAD2-2 and Ol FAD2-3）.Phylogenetic analysis and amino acid comparison showed that Ol FAE1-1 was homologous with Ov FAE1-1,Ol FAE1-2 was homologous with Ov FAE1-2,while Ol FAE1-3 was homologous with At KCS17.Ol FAD2-2 was homologous to Lf FA12H,whereas far related to Ov FAD2-2.Ol FAD2-1 and Ol FAD2-3 were clustered in the same branch with other FAD2 genes.On the one hand,the study of the O.limprichtianus genome can help us better understand the evolution of Brassica plants,on the other hand,it can also help us to better exploit the genes related dihydroxy fatty acid metabolism.These results will provide us with important theoretical basis not only for the further study of dihydroxy fatty acids but also for the development of better plant-based lubricants.