2 2 5The Brassica genus contains a diverse range of oilseed and vegetable crops important for human nutrition 1 . Crops of particular agricultural importance include three diploid species, Brassica rapa (AA), Brassica nigra (BB) and Brassica oleracea (CC), and three allopolyploid species, B. napus (AACC), B. juncea (AABB) and Brassica carinata (BBCC). The evolutionary relationships among these Brassica species are described by what is called the 'triangle of U' model 2 , which proposes how the genomes of the three ancestral Brassica species, B. rapa, B. nigra and Brassica oleracae, combined to give rise to the allopolyploid species of this genus. B. juncea formed by hybridization between the diploid ancestors of B. rapa and B. nigra, followed by spontaneous chromosome doubling. Subsequent diversifying selection then gave rise to the vegetable-and oil-use subvarieties of B. juncea. These subvarieties include vegetable and oilseed mustard in China, oilseed crops in India, canola crops in Canada and Australia, and condiment crops in Europe and other regions 3 . Cultivation of B. juncea began in China about 6,000 to 7,000 years ago 4 , and flourished in India from 2,300 BC onward 5 .The genomes of B. rapa, B. oleracea and their allopolyploid offspring B. napus have been published recently [6][7][8] , and are often used to explain genome evolution in angiosperms [6][7][8] . The genomes of all Brassica species underwent a lineage-specific whole-genome triplication 6,7,9 , followed by diploidization that involved substantial genome reshuffling and gene losses 6,10-13 . In general, plant genomes are typically repetitive, polyploid and heterozygous, which complicates genome assembly 14 . The short read lengths of next-generation sequencing hinder assembly through complex regions, and fragmented draft and reference genomes usually lack skewed (G+C)-content sequences and repetitive intergenic sequences. Furthermore, in allopolyploid species, homoeolog expression dominance or bias, and specifically differential homoelog gene expression, has often been detected, for instance in Gossypium [15][16][17] Triticum 18,19 and Arabidopsis 20,21 , but the role of this phenomenon in selection for phenotypic traits remains mechanistically mysterious 22 .We reported here the draft genomes of an allopolyploid, B. juncea var. tumida, constructed by de novo assembly using shotgun reads, single-molecule long reads (PacBio sequencing), genomic (optical) mapping (BioNano sequencing) and genetic mapping, serving to resolve complicated allopolyploid genomes. The multiuse allopolyploid B. juncea genome offers a distinctive model to study the underlying genomic basis for selection in breeding improvement. These findings place this work into the broader context of plant breeding, highlighting The Brassica genus encompasses three diploid and three allopolyploid genomes, but a clear understanding of the evolution of agriculturally important traits via polyploidy is lacking. We assembled an allopolyploid Brassica juncea genome by shotgun and single-m...

BackgroundGut microbiota plays an important role in many metabolic diseases such as diabetes and atherosclerosis. Apolipoprotein E (apoE) knock-out (KO) mice are frequently used for the study of hyperlipidemia and atherosclerosis. However, it is unknown whether apoE KO mice have altered gut microbiota when challenged with a Western diet.MethodsIn the current study, we assessed the gut microbiota profiling of apoE KO mice and compared with wild-type mice fed either a normal chow or Western diet for 12 weeks using 16S pyrosequencing.ResultsOn a western diet, the gut microbiota diversity was significantly decreased in apoE KO mice compared with wild type (WT) mice. Firmicutes and Erysipelotrichaceae were significantly increased in WT mice but Erysipelotrichaceae was unchanged in apoE KO mice on a Western diet. The weighted UniFrac principal coordinate analysis exhibited clear separation between WT and apoE KO mice on the first vector (58.6%) with significant changes of two dominant phyla (Bacteroidetes and Firmicutes) and seven dominant families (Porphyromonadaceae, Lachnospiraceae, Ruminococcaceae, Desulfovibrionaceae, Helicobacteraceae, Erysipelotrichaceae and Veillonellaceae). Lachnospiraceae was significantly enriched in apoE KO mice on a Western diet. In addition, Lachnospiraceae and Ruminococcaceae were positively correlated with relative atherosclerosis lesion size in apoE KO.ConclusionsCollectively, our study showed that there are marked changes in the gut microbiota of apoE KO mice, particularly challenged with a Western diet and these alterations may be possibly associated with atherosclerosis.Electronic supplementary materialThe online version of this article (10.1186/s12944-018-0811-8) contains supplementary material, which is available to authorized users.

SummaryThe Himalayan marmot (Marmota himalayana) is a hibernating mammal that inhabits the high-elevation regions of the Himalayan mountains. Here we present a draft genome of the Himalayan marmot, with a total assembly length of 2.47 Gb. Phylogenetic analyses showed that the Himalayan marmot diverged from the Mongolian marmot approximately 1.98 million years ago. Transcriptional changes during hibernation included genes responsible for fatty acid metabolism in liver and genes involved in complement and coagulation cascades and stem cell pluripotency pathways in brain. Two selective sweep genes, Slc25a14 and ψAamp, showed apparent genotyping differences between low- and high-altitude populations. As a processed pseudogene, ψAamp may be biologically active to influence the stability of Aamp through competitive microRNA binding. These findings shed light on the molecular and genetic basis underlying adaptation to extreme environments in the Himalayan marmot.

Rabbits are a suitable animal model for atherosclerosis due to their sensitivity to dietary cholesterol. Moreover, rabbits have lipoprotein profiles that are more similar to humans than those of other laboratory animals. However, little is known about the transcriptomic information related to atherosclerosis in rabbits. We aimed to determine the changes in the livers of rabbits fed a normal chow diet (control) or high cholesterol diet (HCD) by histological examinations and RNA sequencing analysis. Compared with the control group, the lipid levels and small LDL subfractions in plasma were increased, and aortic atherosclerotic plaques were formed in the HCD group. Most importantly, HCD resulted in lipid accumulation and inflammation in the livers. Transcriptomic analysis of the liver showed that HCD induces 1183 differentially expressed genes (DEGs) that mainly participate in the regulation of inflammation and lipid metabolism. Furthermore, the signaling pathways involved in inflammation and lipid metabolism were enriched by KEGG pathway analysis. In addition, hepatic DEGs of the HCD group were further validated by real-time PCR. These results suggest that HCD causes liver lipid accumulation and inflammatory response. Although the relationships between these hepatic changes and atherogenesis need further investigation, these findings provide a fundamental framework for future research on human atherosclerosis using rabbit models.

Rabbits (Oryctolagus cuniculus) are one of the most widely used animal models for the study of human lipid metabolism and atherosclerosis because they are more sensitive to a cholesterol diet than other experimental animals such as rodents. Currently, two hypercholesterolemic rabbit models are frequently used for atherosclerosis studies. One is a cholesterol-fed wild-type rabbit and the other is the Watanabe heritable hyperlipidemic (WHHL) rabbit, which is genetically deficient in low density lipoprotein (LDL) receptor function. Wild-type rabbits can be easily induced to develop severe hypercholesterolemia with a cholesterol-rich diet due to the marked increase in hepatically and intestinally derived remnant lipoproteins, called β-very low density lipoproteins (VLDL), which are rich in cholesteryl esters. WHHL rabbits are characterized by elevated plasma LDL levels on a standard chow diet, which resembles human familial hypercholesterolemia. Therefore, both rabbit models develop aortic and coronary atherosclerosis, but the elevated plasma cholesterol levels are caused by completely different mechanisms. In addition, cholesterol-fed rabbits but not WHHL rabbits exhibit different degrees of hepatosteatosis. Recently, we along with others have shown that there are many differentially expressed genes in the atherosclerotic lesions and livers of cholesterol-fed rabbits that are either significantly up- or down-regulated, compared with those in normal rabbits, including genes involved in the regulation of inflammation and lipid metabolism. Therefore, dietary cholesterol plays an important role not only in hypercholesterolemia and atherosclerosis but also in hepatosteatosis. In this review, we make an overview of the recent progress in genomic and transcriptomic analyses of hypercholesterolemic rabbits. These transcriptomic profiling data should provide novel insight into the relationship between hypercholesterolemia and atherosclerosis or hepatic dysfunction caused by dietary cholesterol.