Pervasive prophage recombination occurs during evolution of spore-forming Bacilli

Phages are the main source of within-species bacterial diversity and drivers of horizontal gene transfer, but we know little about the mechanisms that drive genetic diversity of these mobile genetic elements (MGEs). Recently, we showed that a sporulation selection regime promotes evolutionary changes within SPβ prophage of Bacillus subtilis, leading to direct antagonistic interactions within the population. Herein, we reveal that under a sporulation selection regime, SPβ recombines with low copy number phi3Ts phage DNA present within the B. subtilis population. Recombination results in a new prophage occupying a different integration site, as well as the spontaneous release of virulent phage hybrids. Analysis of Bacillus sp. strains suggests that SPβ and phi3T belong to a distinct cluster of unusually large phages inserted into sporulation-related genes that are equipped with a spore-related genetic arsenal. Comparison of Bacillus sp. genomes indicates that similar diversification of SPβ-like phages takes place in nature. Our work is a stepping stone toward empirical studies on phage evolution, and understanding the eco-evolutionary relationships between bacteria and their phages. By capturing the first steps of new phage evolution, we reveal striking relationship between survival strategy of bacteria and evolution of their phages.Subject terms: Bacterial genetics, Evolution     

Hepatic hexokinase domain containing 1 (HKDC1) improves whole body glucose tolerance and insulin sensitivity in pregnant mice

Hexokinase domain containing 1, a recently discovered putative fifth hexokinase, is hypothesized to play key roles in glucose metabolism. Specifically, during pregnancy in a recent genome wide association study (GWAS), a strong correlation between HKDC1 and 2-h plasma glucose in pregnant women from different ethnic backgrounds was shown. Our earlier work also reported diminished glucose tolerance during pregnancy in our whole body HKDC1 heterozygous mice. Therefore, we hypothesized that HKDC1 plays important roles in gestational metabolism, and designed this study to assess the role of hepatic HKDC1 in whole body glucose utilization and insulin action during pregnancy. We overexpressed human HKDC1 in mouse liver by injecting a human HKDC1 adenoviral construct; whereas, for the liver-specific HKDC1 knockout model, we used AAV-Cre constructs in our HKDC1^fl/fl mice. Both groups of mice were subjected to metabolic testing before and during pregnancy on gestation day 17–18. Our results indicate that hepatic HKDC1 overexpression during pregnancy leads to improved whole-body glucose tolerance and enhanced hepatic and peripheral insulin sensitivity while hepatic HKDC1 knockout results in diminished glucose tolerance. Further, we observed reduced gluconeogenesis with hepatic HKDC1 overexpression while HKDC1 knockout led to increased gluconeogenesis. These changes were associated with significantly enhanced ketone body production in HKDC1 overexpressing mice, indicating that these mice shift their metabolic needs from glucose reliance to greater fat oxidation and ketone utilization during fasting. Taken together, our results indicate that hepatic HKDC1 contributes to whole body glucose disposal, insulin sensitivity, and aspects of nutrient balance during pregnancy.     

Complementary developmental expression of the two tyrosine hydroxylase transcripts in zebrafish

Tyrosine hydroxylase (TH) is a rate-limiting enzyme in the biosynthesis of catecholamines. In zebrafish, two genes encoding TH have been identified. We cloned them and studied their expression in zebrafish. In adult tissues, th1 mRNA was more abundant than th2 mRNA in the brain and eyes, whereas th2 mRNA was more abundant in the liver, kidney, heart and gills. In developing brain, th1 mRNA was readily detected at 1 day post-fertilization using qPCR and in situ hybridization, whereas th2 mRNA appeared later. th1 was found in 17 catecholaminergic groups in larval brain, whereas th2 was found in four additional groups. A monoclonal antibody commonly used against TH detected preferentially TH1 protein. The two th genes, probably originated as a result of genome duplication, thus show complementary expression, although th1 is predominant in the brain and th2 in the periphery. th2 may be a novel essential factor in regulation of catecholamine synthesis in zebrafish.     

Somatic embryogenesis and plant regeneration inAzadirachta indica A. Juss

Summary Media for induction of somatic embryogenesis from immature cotyledonary tissues ofAzadirachta indica (Neem) were determined. Callus was initiated on Murashige and Skoog medium supplemented with 0.5 mg·liter⁻¹ of indol-3 acetic acid, 1.0 mg·liter⁻¹ of 6-benzyl amino purine, and 1000 mg·liter⁻¹ of casein hydrolysate. Effect of kinetin was also studied for embryo induction. Carbohydrate source in the form of sucrose and glucose alone and in combination was tested for embryogenic efficiency. Seventy percent embryos showed germination. Healthy plants were potted in sand and soil. Histologic studies confirmed indirect somatic embryogenesis.