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The Effects And Mechanisms On Photosynthesis System Of Green Algae After Carbon Ions Irradiation

Posted on:2017-01-14Degree:DoctorType:Dissertation
Country:ChinaCandidate:J WangFull Text:PDF
GTID:1220330503964386Subject:Biophysics
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Microalgae have been considered as the third generation feedstocks for biofuel and biomaterials. Industrial application of microalgae not only need high metabolic products but also need high biomass. High biomass is related with high photosynthetic efficiency. Recently, researchers have found promising application strains irradiated by heavy ions beam, and also have found chlorophyll deficient mutants. There is seldom reports about the effects and mechanisms of photosynthetic system in green algae after carbon ions irradiation in domestic. This research could be a good supplement for this field. Investigation of heavy ions irradiation mechanism on photosystem of green algae also provide reliable theoretical basis for microalgae breeding. Little research about the changes of proteome level which direct related with the phenotype. Therefore this research provides new perspective for mechanisms of heavy ions irradiation through proteomics. This thesis is about three parts of effects and mechanisms of two common freshwater microalgae species Scenedesmus quadricauda and Selenastrum capricornutum after carbon ions irradiation. The first part is about the dose and time effects of major light harvesting complex(LHC) proteins and pigments of two green algae within 48 h after irradiated by carbon ions beam. The second part is about the photosynthetic features and transcriptional levels of LHC proteins of Selenastrum capricornutum progenies. The third part is about the proteomics research and photosynthetic features on progenies of Scenedesmus quadricauda. The main results are as following:(1) Different doses of carbon-ion irradiation had benefits on improvement of photosynthetic efficiency of Scenedesmus quadricauda within 24-48 h. The improvement of photosynthetic efficiency of 20 Gy was more fast than that of the 60 Gy and 120 Gy. The photosynthetic efficiency of 20 Gy of Selenastrum capricornutum were improved after 24 h.(2) 20 Gy of Scenedesmus quadricauda started the photoprotection more fast than the other doses of Scenedesmus quadricauda. Selenastrum capricornutum started the photoprotection after different doses irradiation. 20 Gy of Scenedesmus quadricauda generated less 3Chl* at 4 h. 60 Gy of Selenastrum capricornutum generated more 3Chl* after 24 h.(3) 20 Gy carbon ions irradiation had markedly influence on transcriptional levels of Lhcb1 and Lhcb2 in the two green algae.(4) Five progenies of Selenastrum capricornutum deficient in chlorophyll a were isolated after carbon-ion exposure. Photosynthetic efficiency, photoprotection ability and the expression of light-harvesting antennae in 5 Selenastrum capricornutum progenies can be markedly influenced after carbon-ion irradiation.(5) Six progenies of Scenedesmus quadricauda deficient in chlorophyll a were isolated after carbon-ion exposure. The biomass of S-26# was higher than that of the wild type, and the biomass of S-4# was the lowest among the six progenies. After analyzing the proteomics data of the two progenies, several differential proteins were found from LHCs. The most differential photosystem proteins of S-4# were Lhcb1、Lhcb2 and Lhcb5(CP26) after q PCR verified. The most differential photosystem expressed proteins of S-26# were Lhcb1、Lhca5.(6) Combined the Fv/Fm and rapid light curves of ΦPSII results of S-4#, it indicates 100 μmol photons m-2 s-1 was beyond S-4# ability, so the low photosynthetic of S-4# could cause photoinhibition. According to the results of Fv/Fm and ΦPSII of S-26#, PSII reaction center of S-26# was more complete than that of the wild type.(7) Lhcb2 protein is related with thermal dissipation ability. Because Lhcb2 protein of S-4# was upregulated, thermal dissipation ability of S-4# indeed was remarkable higher than that of the wild type after exposure to high light. Thermal dissipation ability of S-26# was stronger than the wild type within exposure to high light 6 h, and no more 3Chl* generated after exposure to high light for a long time. Therefore, S-26# could have ability to defend high light exposure.In summary, It can be concluded that carbon ions beam have markedly influenced on transcriptional and expressions levels of Lhcb1 and Lhcb2 proteins of the green algae, photosynthetic efficiency and photoprotection ability from both the effects research and progenies photosynthetic features investigation. Meanwhile, progeny with low photosynthetic ability and progeny which has strong ability to defend high light were found for further investigation.
Keywords/Search Tags:carbon-ion beam, Scenedesmus quadricauda, light harvesting antenna, chlorophyll fluorescence, xanthophyll cycle, proteomics
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