Project description:Higher aridity and more extreme rainfall events in drylands are predicted under climate change. Yet it is unclear how changing precipitation regimes may affect nitrogen (N) cycling, especially in areas with extremely high aridity. Here we investigated soil N isotopic values (M-NM-415N) along a 3200 km aridity gradient and show a hump-shaped relationship between soil M-NM-415N and aridity index (AI) with a threshold at AI=0.32. Also, using a micro-array metageomics tool named GeoChip 5.0, we showed that Variations of nitrification and denitrification gene abundance along the gradient which provide further evidence for the existence of this threshold. Data support the hypothesis that the increase of gaseous N losses is higher than the increase of net plant N accumulation with increasing AI below AI=0.32, while the opposite is favoured above this threshold. Our results suggest the importance of N-cycling microbes in extremely dry areas and the different controlling factors of N cycling on the either side of the threshold.
Project description:Chemosynthetic symbioses occur worldwide in marine habitats, but comprehensive physiological studies of chemoautotrophic bacteria thriving on animals are scarce. Stilbonematinae are coated by monocultures of thiotrophic Gammaproteobacteria. As these nematodes migrate through the redox zone, their ectosymbionts experience varying oxygen concentrations. Here, by applying omics, Raman microspectroscopy and stable isotope labeling, we investigated the effect of oxygen on the metabolism of Candidatus Thiosymbion oneisti. Unexpectedly, sulfur oxidation genes were upregulated in anoxic relative to oxic conditions, but carbon fixation genes and incorporation of 13C-labeled bicarbonate were not. Instead, several genes involved in carbon fixation, organic carbon assimilation and polyhydroxyalkanoate (PHA) biosynthesis, as well as nitrogen fixation and urea utilization were upregulated in oxic conditions. Furthermore, in the presence of oxygen, stress-related genes were upregulated together with vitamin biosynthesis genes likely necessary to withstand its deleterious effects, and fewer symbionts were detected to divide. Based on this first global physiological study of an uncultured chemosynthetic ectosymbiont, we propose that, in anoxic sediment, its proliferation is powered by anaerobic sulfur oxidation coupled to denitrification, whereas in upper layers it makes use of aerobic respiration to facilitate assimilation of carbon and nitrogen, and to survive oxidative stress. The ectosymbiont’s versatile metabolism is thus well-adapted to exploiting a highly changeable environment.
Project description:Maize and rice are the two most economically important grass crops and utilize distinct forms of photosynthesis to fix carbon: C4 and C3 respectively. Relative to C3 photosynthesis, C4 photosynthesis reduces photorespiration and affords higher water and nitrogen use efficiencies under hot arid conditions. To define key innovations in C4 photosynthesis, we profiled metabolites and gene expression along a developing leaf gradient. A novel statistical method was implemented to compare transcriptomes from these two species along a unified leaf developmental gradient and define candidate cis-regulatory elements and transcription factors driving photosynthetic gene expression. We also present comparative primary and secondary metabolic profiles along the gradients that provide new insight into nitrogen and carbon metabolism in C3 and C4 grasses. These resources, including community viewers to access and mine these datasets, will enable the elucidation and engineering of C4 photosynthetic networks to improve the photosynthetic capacity of C3 and C4 grasses.
2014-10-12 | GSE54274 | GEO
Project description:Spatial and temporal variability of microbial communities and salt distributions across an aridity gradient before and after heavy rains in the Atacama Desert
Project description:Colonization of deep-sea hydrothermal vents by invertebrates was made efficient through their adaptation to a symbiotic lifestyle with chemosynthetic bacteria, the primary producers of these ecosystems. Anatomical adaptations such as the establishment of specialized cells or organs have been evidenced in numerous deep-sea invertebrates. However, very few studies detailed global inter-dependencies between host and symbionts in these ecosystems. In this study, we proposed to describe, using a proteo-transcriptomic approach, the effects of symbionts on the deep-sea mussel Bathymodiolus azoricus’ molecular biology. We induced an in situ depletion of symbionts and compared the proteo-transcriptome of the gills of mussels in three conditions: symbiotic mussels (natural population), symbiont-depleted mussels and aposymbiotic mussels
Project description:Maize and rice are the two most economically important grass crops and utilize distinct forms of photosynthesis to fix carbon: C4 and C3 respectively. Relative to C3 photosynthesis, C4 photosynthesis reduces photorespiration and affords higher water and nitrogen use efficiencies under hot arid conditions. To define key innovations in C4 photosynthesis, we profiled metabolites and gene expression along a developing leaf gradient. A novel statistical method was implemented to compare transcriptomes from these two species along a unified leaf developmental gradient and define candidate cis-regulatory elements and transcription factors driving photosynthetic gene expression. We also present comparative primary and secondary metabolic profiles along the gradients that provide new insight into nitrogen and carbon metabolism in C3 and C4 grasses. These resources, including community viewers to access and mine these datasets, will enable the elucidation and engineering of C4 photosynthetic networks to improve the photosynthetic capacity of C3 and C4 grasses. [Maize] Nine day old third leaves of maize were cut into fifteen 1 cm segments; samples were pooled from an average of seven plants per biological replicate and six biological replicates in total were collected on different dates. [Rice] 14 day old third leaves of rice were cut into eleven 2 cm segments, samples were pooled from an average of 15 plants per biological replicate and four replicates in total were collected.