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The molecular impacts of abiotic stress factors on photosynthesis in cyanobacteria and higher plants

The molecular impacts of abiotic stress factors on photosynthesis in cyanobacteria and higher plants

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LOHSCHEIDER, Jens Nikolaus, 2010. The molecular impacts of abiotic stress factors on photosynthesis in cyanobacteria and higher plants

@phdthesis{Lohscheider2010molec-8524, title={The molecular impacts of abiotic stress factors on photosynthesis in cyanobacteria and higher plants}, year={2010}, author={Lohscheider, Jens Nikolaus}, address={Konstanz}, school={Universität Konstanz} }

<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:bibo="http://purl.org/ontology/bibo/" xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:dcterms="http://purl.org/dc/terms/" xmlns:xsd="http://www.w3.org/2001/XMLSchema#" > <rdf:Description rdf:about="https://kops.uni-konstanz.de/rdf/resource/123456789/8524"> <dc:contributor>Lohscheider, Jens Nikolaus</dc:contributor> <dcterms:title>The molecular impacts of abiotic stress factors on photosynthesis in cyanobacteria and higher plants</dcterms:title> <dc:format>application/pdf</dc:format> <dcterms:alternative>Der Einfluß abiotischer Streßfaktoren auf die Photosynthese in Cyanobakterien und höheren Pflanzen auf molekularer Ebene</dcterms:alternative> <dc:language>eng</dc:language> <bibo:uri rdf:resource="http://kops.uni-konstanz.de/handle/123456789/8524"/> <dc:creator>Lohscheider, Jens Nikolaus</dc:creator> <dc:date rdf:datatype="http://www.w3.org/2001/XMLSchema#dateTime">2011-03-24T17:44:23Z</dc:date> <dcterms:issued>2010</dcterms:issued> <dc:rights>deposit-license</dc:rights> <dcterms:abstract xml:lang="eng">During photosynthesis, the physical energy of sunlight is used for the production of biomass, consuming atmospheric CO2 and water and at the same time releasing molecular oxygen. This process is tightly regulated and its efficiency is strongly dependent on external abiotic and biotic factors influencing the status of the photosynthetic machinery, and thus, all downstream molecular processes. Light plays a central role because variations of light intensity and quality are frequent in most habitats. This causes the requirement of acclimation mechanisms in the photosynthetic cells in order to guarantee optimal activity of physiological processes. Photosynthetic organisms have developed a variety of cellular and molecular mechanisms to acclimate to conditions when light is limiting as well as to avoid or repair damage caused by high light (HL) intensities. At HL intensities, reactive oxygen species (ROS) are generated during photosynthesis, which lead to damage of cellular components. On the molecular level, photosynthetic organisms can prevent this photooxidative damage by adjusting the size of their light-harvesting antennae, by effective repair mechanisms of damaged cell components, by direct detoxification of ROS via protective molecules or enzymatic radical scavenging systems, and by the induction of light stress proteins. The family of early light-induced proteins (ELIP) has been described to be involved in protection against photooxidative damage in cyanobacteria and photosynthetic eukaryotes. They presumably act as quenchers of excess light energy. Although the stress-enhanced proteins (SEP) represent the dominant members of the ELIP family in Arabidopsis thaliana, they are not well studied yet. Therefore in this study, mRNA data concerning the expression patterns of SEPs in different organs as well as during the plant s life cycle were verified on the protein level. In order to determine the role of SEPs in photoprotection, localisation studies of these proteins inside the cell were performed for selected SEP members. The results revealed association of all investigated SEPs with photosystem II (PSII). For studies of the physiological functions of SEPs in higher plants, mutant and transgenic A. thaliana lines were identified and used in light stress experiments. While mutants with reduced amounts of SEP3a did not show significant differences as compared to wild type plants, sep3a over-expressor mutant lines developed a circular chlorosis of the leaf rosette, in which chlorophyll fluorescence parameters were altered. This implied a function of SEPs in stabilisation of PSII and/or a role in pigment biosynthesis. Apart from induction of ELIPs under high light (HL) conditions, the arrangement of the photosystems antenna is changed and photodamaged proteins are exchanged by newly-synthesised copies. In a process called state transition, mobile parts of the PSII antenna become phosphorylated and migrate to PSI to balance energy fluxes between the two photosystems. In this study, novel light-regulated phosphorylation sites are described. Moreover, nitrations at the D1 protein were discovered, which might act as degradation signal of the damaged PSII reaction centres. Furthermore, the impact of light stress on different cyanobacteria was analysed. It could be shown that the vertical distribution of closely related Synechococcus isolates from Lake Constance is influenced by their genetically fixed mechanisms for stress protection. While phycocyanin-rich strains isolated from the water surface were stress resistant, phycoerythrin-rich isolates from deeper water areas of the littoral zone displayed a reduction in pigment and protein concentrations after HL exposure. In contrast, analysis of the marine cyanobacterium Trichodesmium erythraeum exposed to HL and low light conditions indeed revealed a reduction of pigment concentrations and increased growth rates. This indicates effective acclimation mechanisms in Trichodesmium reflecting the environmental variations in the natural habitat. Apart from variations in the light regime, nutrient availability strongly influences the photosynthetic capacity of cyanobacteria, algae and higher plants. Obviously, macronutrients like phosphorus, nitrogen and carbon are important for cellular biomass production and are usually the factors limiting plant growth. However, micronutrients may also be limiting because they act as important cofactors necessary for general function or regulation of proteins. In the oceans, cyanobacterial and algal growth is strongly limited by the availability of iron, which is an essential cofactor in proteins involved in photosynthetic reactions and cellular respiration as well as in the enzyme nitrogenase which is responsible for the fixation of atmospheric nitrogen. The effects of iron limitation on the marine filamentous cyanobacterium Trichodesmium were studied by showing it s impact on photosynthesis and nitrogen fixation.</dcterms:abstract> <dcterms:available rdf:datatype="http://www.w3.org/2001/XMLSchema#dateTime">2012-07-31T22:25:05Z</dcterms:available> <dcterms:rights rdf:resource="http://nbn-resolving.org/urn:nbn:de:bsz:352-20140905103416863-3868037-7"/> </rdf:Description> </rdf:RDF>

Dateiabrufe seit 01.10.2014 (Informationen über die Zugriffsstatistik)

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