The cyanobacterium–Azolla symbiosis: Interactions and cell differentiation
2007 (English)In: Abstracts of the Annual Main Meeting of the Society for Experimental Biology, Glasgow, Scotland, 31st March - 4th April, 2007, 2007Conference paper (Other (popular science, discussion, etc.))
Selected cyanobacteria form stable nitrogen-fixing symbioses with diverse eukaryotes. The water-fern Azolla carries a nitrogen-fixing cyanobacterium (cyanobiont) in its leaves and shows a pronounced intimacy between its partners. It is the only perpetual N2-fixing symbiosis, i.e. the cyanobiont is vertically transmitted in sporocarps between plant generations. The cyanobiont also seems incapable of independent growth which may suggest gene loss and that the symbiosis is on its way to evolve into a N2-fixing plant. Proteomic analyses of the cyanobiont (2-D coupled to MS) resulted in an identification of about 79% of proteins analysed. Processes upregulated were related to energy production, nitrogen and carbon metabolism and stress, while photosynthesis and metabolic turnover rates were downregulated, stressing a slow heterotrophic mode of growth, high heterocyst frequencies and nitrogen-fixing capacities. Peptide mass spectra of NifH demonstrated the presence of a 300–400 Da protein modification localized to a 13 amino acid sequence. Additionally, a short phylogenetic distance between the cyanobiont and some sequenced cyanobacteria (Section IV) and the database hits of the proteins identified by proteomics, together suggest that the Azolla cyanobiont may represent a novel cyanobacterial genus. The genome of the cyanobiont will be sequenced in 2007 (DOE/JGI, USA).
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IdentifiersURN: urn:nbn:se:su:diva-11028DOI: doi:10.1016/j.cbpa.2007.01.475OAI: oai:DiVA.org:su-11028DiVA: diva2:177547