Copper Disturb Electron Transfer And Induce Oxidative Damage In Phaeodactylum Tricornutum

Because of the anthropogenic activities,such as industrial and domestic wastes disposal,copper mine drainage,and antifouling paints mining etc,copper(Cu)has been gradually accumulate in aquatic environments and become one of the most toxic metals in phytoplankton.Algae are the primary producers of aquatic system and have been widelyused in ecological risk assessment to evaluate the impacts of contamination.In this study,we examine the toxicity targets of Cu in the modeled marine diatom,Phaeodactylum tricornutum,on the physiological,biochemical,structural and genetic levels.The results showed that the growth of P.tricornutum was inhibited exposure to Cu,and With the increase of Cu treated concentration,the percent inhibition increased and reached 1.1%,0.3%,32.1%,48.9%,55.2%,60.8%and 63.1%after 96 h of exposure to 10,20,40,60,80,100 and 150?M Cu,respectively.Based on these results,we selected 20,40 and 60 ?M Cu concentrations for subsequent exposure experiments.The toxicity of Cu also reflected in the decrease of chlorophylls and carotenoids content.By measuring the content of metal ions in the algae cells,we found that Fe,Na,Mg,K and Ca Significant increase in medium containing 40 and 60 ?M Cu,and significant decrease of Mn and no change in content of Zn in Cu-treated groups,implicating that copper destroyed the ion balance of algal cell.Cu can cause algal cell oxidative injure,and the results of laser confocal microscope observation and fluorescence detection showed that high concentration of Cu treatment accumulated high concentration of ROS.Furthermore,the content of MDA increased in Cu-treated groups,alsosuggesting that algae cells suffered oxidative damage.Our results from flow cytometry showed that Cu accelerated cell proliferation by inducing the conversion of G0/G1 phase to G2/M phase.By analyzing the transcript levels of cell division-related gene,ftsH,we found that the transcript of ftsH was significantly increased after 96 h of exposure to 40 and 60 ?M Cu.This result indicating that Cu toxicity was torupture algae cells,but not inhibit cell division.Cu can disturb the electron transfer,by analyzing the transcript levels of electron transfer chain of respiratory(nad5,SDH2,cox3 and atpA)and photosynthetic-related genes(psbD,petD,psaB,petF and rbcL),we found that these genes were significantly decreased after 48 h of exposure to 20 and 40 ?M Cu,and the transcripts of these genes increased in a dose-dependent manner after 96 h of exposure to Cu-treated groups.Our results also indicated that the Fe had an effect on alleviation toxicity of Cu.