Degradation Mechanism Of Pyrene By Scripus Triqueter And Its Rhizosphere In The Simulated Wetland

Scirpus triqueter, a dominant species in wetland of Huangpu River, was firstly used asphytoremediation plant. Pyrene was used as objective contaminant. The objectives of thisstudy were:(1) to estimate the dissipation ratios of pyrene in the presence of S. triqueter;(2)to ascertain the growth parameters and physiological response of S. triqueter after pyrenetreatment;(3) to study the changes of the soil enzymes in different parts of the soils afterpyrene treatment at the presence of S. triqueter;(4) to investigate the response of themicrobial communities to pyrene and S. triqueter;(5) finally, to elucidate the molecularmechanism of S. triqueter in response to pyrene by using proteomic method. The majorfindings are summarized as follow:(1) The dissipation ratios of pyrene were enhanced at the presence of S. triqueter, thedissipation ratio was up to70%after80-day treatment. Pyrene contaminated soil inhibited thegrowth of S. triqueter.10-40mg·kg–1of pyrene could reduce activities of catalase (CAT), andthen the activities would increase with increasing pyrene concentration. At the early growthstage of S. triqueter, the peroxidase (POD) activity of shoot was inhibited at first, and thenwas stimulated with increasing pyrene concentration; however, the activity experienced theprocess of stimulation-inhibition-stimulation at the vigorous stage. The activity of superoxidedismutase (SOD) declined with increasing pyrene concentration. Activity of CAT in shootwas higher than that in root, while the activities of POD and SOD in root were higher thanthose in shoot. Enzyme activities exhibited significant differences in different growth stages.(2) The CAT activities of soils were promoted at lower pyrene concentrations and wereinhibited at higher pyrene concentrations; CAT activities in the rhizospheric soils increasedgreatly compared to those in the bulk and unplanted soils at the vigorous and reproductivestage of S. triqueter. The activities of POD in soils were inhibited by prene at the reproductivestage of S. triqueter. When the concentration range of pyrene was from5to20mg·kg–1, thepolyphenoloxidase (PPO) activities of bulk and unplanted soils at the vigorous stage andthose of rhizospheric soils at the reproductive stage were significantly positively related topyrene. However, the dehydrogenase (DHA) activities of soils were significantly negativelyrelated to pyrene; moreover, PPO activities in the rhizospheric soils were higher than those in the bulk and unplanted soils. The growth stage of S. triqueter was the main impact factor tothe activities of soil enzymes; the effects of pyrene concentration and the interactionsbetween growth stages and pyrene concentration on the activities of soil enzymes dependedon the type of enzyme and soil handling.(3) High pyrene concentration reduced the populations of some bacteria, fungi andactinomyces, but increased pyrene-tolerant bacteria abundance. It is important that S.triqueter is favorable for the growth of microorganisms. The pH and organic matter of soilwere important parameters to the growth of microorganism.(4) The biomass of soil microbes declined after pyrene treatment, however, the biomassincreased at the presence of S. triqueter. Bacteria were more tolerant to pyrene than fungi;while Gram-positive bacteria showed a greater tolerance than Gram-negative bacteria. Theintroduction of S. triqueter was benefit to fungi, Gram-negative bacteria and aerobic bacteria.Additionally, there was discrimination in microbial community structure under the stress ofpyrene from the principal component analysis (PCA).(5) After treated by pyrene, a total of37protein spots from culm showed significantchanges, among which, the expression levels of13protein spots were downregulated,24protein spots were upregulated. A total of55protein spots from root showed significantchanges, and36protein spots were downregulated,19protein spots were upregulated.Protein spots which were significantly regulated by pyrene were identified by massspectrometry. A total of17and7proteins were successfully identified in shoot and root,respectively.(6) The identified proteins were grouped according to functional categories. Proteins inshoot included: photosynthesis related protein, defense related protein, energy and materialmetabolism related protein, coenzyme metabolism related protein and protein metabolismrelated protein. Proteins involved in photosynthesis accounted for more than70%of theidentified proteins of shoot. The proteins in root included: stress response related proteins,defense related protein, energy and material metabolism related protein and proteinmodification related protein. Pyrene affected the photosynthesis of S. triqueter seriously,simultaneously, had an impact on the multiple metabolic processes, protein synthesis andsignal transduction.