By analyzing successive lifestyle stages of a model Rhizobium–legume symbiosis using mariner-based transposon insertion sequencing (INSeq), we have defined the genes required for rhizosphere growth, root colonization, bacterial infection, N2-fixing bacteroids, and release from legume (pea) nodules. While only 27 genes are annotated as nif and fix in Rhizobium leguminosarum, we show 603 genetic regions (593 genes, 5 transfer RNAs, and 5 RNA features) are required for the competitive ability to nodulate pea and fix N2. Of these, 146 are common to rhizosphere growth through to bacteroids. This large number of genes, defined as rhizosphere-progressive, highlights how critical successful competition in the rhizosphere is to subsequent infection and nodulation. As expected, there is also a large group (211) specific for nodule bacteria and bacteroid function. Nodule infection and bacteroid formation require genes for motility, cell envelope restructuring, nodulation signaling, N2 fixation, and metabolic adaptation. Metabolic adaptation includes urea, erythritol and aldehyde metabolism, glycogen synthesis, dicarboxylate metabolism, and glutamine synthesis (GlnII). There are 17 separate lifestyle adaptations specific to rhizosphere growth and 23 to root colonization, distinct from infection and nodule formation. These results dramatically highlight the importance of competition at multiple stages of a Rhizobium–legume symbiosis.
Liver glycogen, a highly branched polymer of glucose, is important for maintaining blood-glucose homeostasis. It was recently shown that db/db mice, a model for Type 2 diabetes, are unable to form the large composite glycogen α particles present in normal, healthy mice. In this study, the structure of healthy mouse-liver glycogen over the diurnal cycle was characterized using size exclusion chromatography and transmission electron microscopy. Glycogen was found to be formed as smaller β particles, and then only assembled into large α particles, with a broad size distribution, significantly after the time when glycogen content had reached a maximum. This pathway, missing in diabetic animals, is likely to give optimal blood-glucose control during the daily feeding cycle. Lack of this control may contribute to, or result from, diabetes. This discovery suggests novel approaches to diabetes management.
41 42 By analyzing successive lifestyle stages of a model Rhizobium-legume symbiosis using 43 mariner-based transposon insertion sequencing (INSeq), we have defined the genes 44 required for rhizosphere growth, root colonization, bacterial infection, N2-fixing 45 bacteroids and release from legume (pea) nodules. While only 27 genes are annotated 46 as nif and fix in Rhizobium leguminosarum, we show 603 genetic regions (593 genes, 5 47 tRNAs and 5 RNA features) are required for the competitive ability to nodulate pea and 48 fix N2. Of these, 146 are common to rhizosphere growth through to bacteroids. This 49 large number of genes, defined as rhizosphere-progressive, highlights how critical 50 successful competition in the rhizosphere is to subsequent infection and nodulation. As 51 expected, there is also a large group (211) specific for nodule bacteria and bacteroid 52 function. Nodule infection and bacteroid formation require genes for motility, cell 53 envelope restructuring, nodulation signalling, N2 fixation, and metabolic adaptation. 54 Metabolic adaptation includes urea, erythritol and aldehyde metabolism, glycogen 55 synthesis, dicarboxylate metabolism and glutamine synthesis (GlnII). There are 56 separate lifestyle adaptations specific to rhizosphere growth (17) and root colonization 57 (23), distinct from infection and nodule formation. These results dramatically highlight 58
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