Toxicity and mechanisms of atrazine to the photosynthetic physiology and central carbon metabolism of Phaeodactylum tricornutum, at environmental dose

Atrazine is one of the most commonly used herbicide and has been frequently detected in estuarine and offshore waters worldwide. As a photosystem Ⅱ inhibitor, atrazine may inhibit phytoplankton from fixating of CO2 and alter its carbon metabolism, which will undoubtedly have negative effect on the primary productivity and carbon sequestration capacity of coastal waters. However, the existing reports mainly focused on agriculture and freshwater ecosystems and are mostly toxicity test with high-dose of atrazine, which have little concern about the negative effects of atrazine on the carbon metabolism of phytoplankton and can’t reflect the actual toxic situation in offshore water. Diatoms are widely distributed in freshwater and oceans and contribute at least 20% of the global CO2 assimilation, which is an ideal model group to assess the ecological risk of atrazine. Here we present a comprehensive analysis of the physiological and genome-wide gene expression characteristics of the diatom P. tricornutum Pt-1 (CCMP 2561) treated with environmental dose of atrazine at different stress stages. 18 samples were analysed as following: 1) D1-C, P. tricornutum Pt-1 inoculated in uncontaminated culture medium for 12 hours; 2) D1-T, P. tricornutum Pt-1 inoculated in atrazine-contaminated culture medium for 12 hours; 3) D2-C, P. tricornutum Pt-1 inoculated in uncontaminated culture medium for 2 days ; 4)D2-T, P. tricornutum Pt-1 inoculated in atrazine-contaminated culture medium for 2 days; 5) D7-C, P. tricornutum Pt-1 inoculated in uncontaminated culture medium for 7 days ; 6) D7-T, P. tricornutum Pt-1 inoculated in atrazine-contaminated culture medium for 7 days. Three replicates were set up for each treatment.