The rhizosphere is defined as the area of soil surrounding plant roots, which is influenced by plant exudates. The rhizosphere hosts a diverse and dynamic microbiome, which is shaped by both plant and environmental factors. The plant-microbe and microbe-microbe functional interactions which occur in the rhizosphere can have significant impacts on plant growth. Developing understanding of the composition, functions and interactions of the rhizosphere microbiome and the factors which shape it, may prove valuable to improve agricultural sustainability. The rhizosphere and bulk soil microbiomes of contrasting Brassica napus genotypes growing in the field under high and low N inputs were characterised using amplicon sequencing. Taxonomic identification, functional prediction tools and network analysis were used to gauge how nutrient availability and plant genotype influenced the microbiome. N availability was seen to have a greater influence on composition, function and connectivity of the microbiome than crop genotype, with varying effects on microbes from different Kingdoms. Metatranscriptome analysis enables analysis of the functioning of the microbiome. The effectiveness of different methods for the separation of root and rhizosphere soil for metatranscriptome analysis was compared. Washing roots in water to separate roots and rhizosphere soil followed by freeze drying prior to RNA extraction was shown to be the best method to avoid distorting the metatranscriptome profile. Metatranscriptome analysis of field grown B. napus revealed increases in the rhizosphere relative to soil for protein metabolism functions, and the root compartment contained a high proportion of transcripts related to phage activity. Plant rhizosphere functions were investigated using transcriptomic analysis of a diverse range of cultivated and wild Brassica oleracea plants. Uptake of PO4 is a vital plant process but the identity of PO4 transporters is unknown in B. oleracea. A number of putative PHT1 PO4 transporter genes were identified. Significant differences in expression of the putative PHT1 genes were found between cultivated and wild lines, which may inform future plant breeding strategies.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:742244 |
| Date | January 2017 |
| Creators | Hale, Christopher Charles |
| Publisher | University of Warwick |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://wrap.warwick.ac.uk/102344/ |
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