AUTHOR=Wang Xiaoping , Yang Xiyu , Chen Siyu , Li Qianqian , Wang Wei , Hou Chunjiang , Gao Xiao , Wang Li , Wang Shucai 

TITLE=Zinc Oxide Nanoparticles Affect Biomass Accumulation and Photosynthesis in Arabidopsis

JOURNAL=Frontiers in Plant Science

VOLUME=6

YEAR=2016

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2015.01243

DOI=10.3389/fpls.2015.01243

ISSN=1664-462X

ABSTRACT=<p>Dramatic increase in the use of nanoparticles (NPs) in a variety of applications greatly increased the likelihood of the release of NPs into the environment. Zinc oxide nanoparticles (ZnO NPs) are among the most commonly used NPs, and it has been shown that ZnO NPs were harmful to several different plants. We report here the effects of ZnO NPs exposure on biomass accumulation and photosynthesis in <italic>Arabidopsis</italic>. We found that 200 and 300 mg/L ZnO NPs treatments reduced <italic>Arabidopsis</italic> growth by ∼20 and 80%, respectively, in comparison to the control. Pigments measurement showed that Chlorophyll a and b contents were reduced more than 50%, whereas carotenoid contents remain largely unaffected in 300 mg/L ZnO NPs treated <italic>Arabidopsis</italic> plants. Consistent with this, net rate of photosynthesis, leaf stomatal conductance, intercellular CO<sub>2</sub> concentration and transpiration rate were all reduced more than 50% in 300 mg/L ZnO NPs treated plants. Quantitative RT-PCR results showed that expression levels of chlorophyll synthesis genes including <italic>CHLOROPHYLL A OXYGENASE</italic> (<italic>CAO</italic>), <italic>CHLOROPHYLL SYNTHASE</italic> (<italic>CHLG</italic>)<italic>, COPPER RESPONSE DEFECT 1</italic> (<italic>CRD1</italic>)<italic>, MAGNESIUM-PROTOPORPHYRIN IX METHYLTRANSFERASE</italic> (<italic>CHLM</italic>) <italic>and MG-CHELATASE SUBUNIT D</italic> (<italic>CHLD</italic>), and photosystem structure gene <italic>PHOTOSYSTEM I SUBUNIT D-2</italic> (<italic>PSAD2</italic>), <italic>PHOTOSYSTEM I SUBUNIT E-2</italic> (<italic>PSAE2</italic>)<italic>, PHOTOSYSTEM I SUBUNIT K</italic> (<italic>PSAK</italic>) and <italic>PHOTOSYSTEM I SUBUNIT K</italic> (<italic>PSAN</italic>) were reduced about five folds in 300 mg/L ZnO NPs treated plants. On the other hand, elevated expression, though to different degrees, of several carotenoids synthesis genes including <italic>GERANYLGERANYL PYROPHOSPHATE SYNTHASE 6</italic> (<italic>GGPS6</italic>)<italic>, PHYTOENE SYNTHASE</italic> (<italic>PSY</italic>) <italic>PHYTOENE DESATURASE</italic> (<italic>PDS</italic>), and <italic>ZETA-CAROTENE DESATURASE</italic> (<italic>ZDS</italic>) were observed in ZnO NPs treated plants. Taken together, these results suggest that toxicity effects of ZnO NPs observed in <italic>Arabidopsis</italic> was likely due to the inhibition of the expression of chlorophyll synthesis genes and photosystem structure genes, which results in the inhibition of chlorophylls biosynthesis, leading to the reduce in photosynthesis efficiency in the plants.</p>