Combined effect of copper and cadmium on Chlorella vulgaris growth and photosynthesis-related gene transcription
2009
Qian, Haifeng | Li, Jingjing | Sun, Liwei | Chen, Wei | Sheng, G Daniel | Liu, Weiping | Fu, Zhengwei
Chlorella vulgaris was tested to assess their toxicities in freshwater contaminated by the metal compounds of copper (Cu) and cadmium (Cd), both singly and combined. Exposure to 0.5 and 1.5μM Cu or 1.0 and 2.0μM Cd alone significantly decreased algal growth and chlorophyll content and increased reactive oxygen species (ROS) content. Two-way ANOVA analysis shows that the combination of these two metal compounds decreased cell growth, chlorophyll content and increased ROS content synergistically. The highest algal cell inhibition was 78.55%, the lowest levels of chl a, chl b and total-chl were 10.59%, 33.33% and 17.94% of the control, respectively. The highest increase in ROS was 9.15-fold greater than that of the control when exposed to Cu(1.5)+Cd(2.0). Real-time PCR shows that Cu and Cd reduced the transcript abundance of psbA and rbcL, but without a synergistic interaction, whereas Cu and Cd increased the transcript abundance of psaB synergistically. These results demonstrate that Cu and Cd independently inhibit PSII activity and CO₂ assimilation, but synergistically increase ROS content to disrupt chlorophyll synthesis and inhibit cell growth.
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