The Preliminary Study On The Molecular Mechanism Of Nitrogen Nutrition Absorption And Metabolism Of Prorocentrum Donghaiense

Prorocentrum donghaiense is considered to be the most harmful algae in the East China sea,because of its ability to form high biomass blooms that cover wide areas and maintain high densities for a long time.Nitrogen is an essential nutrient for phytoplankton in the marine environment as it is the major component of macromolecules.The capacity of P.donghaiense to changing ambient N is essential to their success in the ocean.Therefore,the study on the physiological and molecular mechanism of nitrogen absorption and metabolism of P.donghaiense is of great significance.In this study,P.donghaiense was selected as the research object.P.donghaiense's capability in utilizing DOM released from Skeletonema costatum.Quantitative reverse transcriptase PCR were used to identity the molecular response of P.donghaiense's nitrogen absorption and metabolism genes to different nitrogen source and concentrations.The objective of the thesis was to provide some theoretical foundation for the physiological and molecular mechanism of nitrogen catabolization during the occurrence and persistence of P.donghaiense in coastal waters of china.Results were as follows:1.S.costatum released a broad range of organic compounds.The composition of DOM released by S.costatum were dominated by protein-like DOM and humic-like DOM,P.donghaiense and S.costatum could highly express Leucine aminopeptidase?LAP?and Alkaline phosphatase?AP?to utilizing DOM released from S.costatum.The cell APA and LAP of P.donghaiense was greater than that of S.costatum.P.donghaiense was more sensitive than S.costatum in expression.Large amounts of organic nutrients were released into the environment during the decling phases of S.costatum,The organic nutrients released by S.costatum stimulated the growth of P.donghaiense.2.The study of P.donghaiense's gene in relative to nitrogen absorption and metabolism,Transcript abundances of ammonium transporter?nitrate transporter?glutamine synthetase?nitrite reductase were significantly affected by nitrogen sources and concentrations.Ammonium transporter in the NH₄⁺and urea treatments increased in abundance relative to the NO₃^-control treatments.Transcript abundance of glutamine synthetase was highest in the NO₃^-treatments.Transcript abundances of nitrate transporter?nitrate reductase?nitrite reductase decreased in abundance at the oneset of nitrogen starvation.Interestingly ammonium transporter?glutamine synthetase was induced during the stages of nitrogen deprivation.3.The study of P.donghaiense's gene in relative to urea cycle.Transcript abundances of ornithine aminotransferase and arginase were significantly affected by nitrogen sources and concentrations.Transcript abundances of ornithine aminotransferase and arginase decreased in abundance at the oneset of nitrogen starvation.Results showed that,P.donghaiense could efficiently regenerate DOM for growth,and that the avability of abundant DOM favor P.donghaiense growth.P.donghaiense possess a full nitrogen absorption?metabolism and urea cycle genes,and that transcript abundances of these genes were significantly affected by nitrogen sources and concentrations,this might favor P.donghaiense growth and even dominance in natural communities when the nitrogen was limitation or the nitrogen sources were different.