Project description:Anthropogenic activities have dramatically increased the inputs of reactive nitrogen (N) into terrestrial ecosystems, with potentially important effects on the soil microbial community and consequently soil C and N dynamics. Our analysis of microbial communities in soils subjected to 14 years of 7 g N m-2 year-1 Ca(NO3)2 amendment in a Californian grassland showed that the taxonomic composition of bacterial communities, examined by 16S rRNA gene amplicon sequencing, was significantly altered by nitrate amendment, supporting the hypothesis that N amendment- induced increased nutrient availability, yielded more fast-growing bacterial taxa while reduced slow-growing bacterial taxa. Nitrate amendment significantly increased genes associated with labile C degradation (e.g. amyA and xylA) but had no effect or decreased the relative abundances of genes associated with degradation of more recalcitrant C (e.g. mannanase and chitinase), as shown by data from GeoChip targeting a wide variety of functional genes. The abundances of most N cycling genes remained unchanged or decreased except for increases in both the nifH gene (associated with N fixation), and the amoA gene (associated with nitrification) concurrent with increases of ammonia-oxidizing bacteria. Based on those observations, we propose a conceptual model to illustrate how changes of functional microbial communities may correspond to soil C and N accumulation.
2017-11-21 | GSE107168 | GEO
Project description:Jardines de la Reina facultative nitrate reducers
Project description:As multicellular organisms, plants must integrate responses to environmental cues across different cell types and also over time. Nitrate is the major source of available Nitrogen for plants, and a limiting factor for plant growth and productivity. Plant root s are highly impacted by nitrate availability, modifying their architecture to optimize nitrate uptake from soils. In order to understand how this functional response is dynamically orchestrated across different cell types of the root, space and time must be addressed within the same experimental setup. We performed a transcriptomic analysis in five major root cell types of Arabidopsis plants in response to nitrate treatments considering short and long time exposure to this macronutrient. We found nitrate treatment triggers a dynamic reprogramming of root cell gene expression that follows a spatial pattern over time consistent with an early regulation of nitrate transport and assimilation in external layers of the root and a later regulation of hormonal and developmental processes in more internal layers of the root.
Project description:Nitrogen availability in the soil is a major determinant of crop yield. While the application of fertilizer can substantially increase the yield on poor soils, it also causes nitrate pollution of water resources and high costs for farmers. Increasing the nitrogen use efficiency in crop plants is a necessary step to implement low input agricultural systems. We exploited the genetic diversity present in the world-wide Arabidopsis thaliana population to study adaptive growth patterns and changes in gene expression associated with chronic low nitrate stress, with the aim to identify biomarkers associated with good plant performance under low nitrate availability. Transcription and epigenetic factors were identified as important players in the adaptatiion to limited nitrogen in a global gene expression analysis using the Affymetrix ATH1 chip.