Genome and transcriptome of Papaver somniferum Chinese landrace CHM indicates that massive genome expansion contributes to high benzylisoquinoline alkaloid biosynthesis

Opium poppy(Papaver somniferum)is a source of morphine,codeine,and semisynthetic derivatives,including oxycodone and naltrexone.Here,we report the de novo assembly and genomic analysis of P.somniferum traditional landrace‘Chinese Herbal Medicine’.Variations between the 2.62 Gb CHM genome and that of the previously sequenced high noscapine 1(HN1)variety were also explored.Among 79,668 protein-coding genes,we functionally annotated 88.9%,compared to 68.8%reported in the HN1 genome.Gene family and 4DTv comparative analyses with three other Papaveraceae species revealed that opium poppy underwent two whole-genome duplication(WGD)events.The first of these,in ancestral Ranunculales,expanded gene families related to characteristic secondary metabolite production and disease resistance.The more recent species-specific WGD mediated by transposable elements resulted in massive genome expansion.Genes carrying structural variations and large-effect variants associated with agronomically different phenotypes between CHM and HN1 that were identified through our transcriptomic comparison of multiple organs and developmental stages can enable the development of new varieties.These genomic and transcriptomic analyses will provide a valuable resource that informs future basic and agricultural studies of the opium poppy.

Antioxidant response to severe hypoxia in Brandt’s vole Lasiopodomys brandtii

The antioxidant defense system is essential for animals to cope with homeostasis disruption and overcome oxidative stress caused by adverse environmental conditions such as hypoxia.However,our understanding of how this system works in subterranean rodents remains limited.In this study,Brandt’s vole Lasiopodomys brandtii was exposed to normoxia(21%O_(2))or hypoxia(mild or severe hypoxia:10%or 5%O_(2))for 6 h.Changes in key enzymes of the classic enzymatic antioxidant system at both mRNA and enzyme activity levels,and tissue antioxidant levels of the low-molecular-weight antioxidant system were determined in brain,liver,and kidney.Transcript levels of the upstream regulator NF-E2-related factor 2(Nrf2)were also measured.We found that the mRNA expression of Nrf2 and its downstream antioxidant enzyme genes in L.brandtii were relatively conserved in response to hypoxia in most tissues and genes tested,except in the liver.Hepatic Nrf2,Cu/Zn SOD,GPx1,and GPx3 levels were significantly upregulated in response to mild hypoxia,whereas Mn SOD level decreased significantly in severe hypoxia.Unmatched with changes at the RNA level,constitutively high and relatively stable antioxidant enzyme activities were maintained throughout.For the low-molecular-weight antioxidant system,an abrupt increase of cerebral ascorbic acid(AA)levels in hypoxia indicated a tissue-specific antioxidant response.Although hypoxia did not cause significant oxidative damage in most tissues tested,the significant decrease in antioxidant enzyme activities(GPX and GR)and increase in lipid peroxidation in the kidney suggest that prolonged hypoxia may pose a critical threat to this species.