Relative comparison of strobilurin fungicides at environmental levels: Focus on mitochondrial function and larval activity in early staged zebrafish (Danio rerio).

Affiliation

Li XY(1), Qin YJ(1), Wang Y(2), Huang T(3), Zhao YH(3), Wang XH(4), Martyniuk CJ(5), Yan B(1).
Author information:
(1)Institute of Environmental Research at Greater Bay Area, Key Laboratory for Water Quality and Conservation of the Pearl River Delta, Ministry of Education, Guangzhou University, Guangzhou, 510006, China.
(2)The New Hope Liuhe Co., Ltd., Qingdao, China.
(3)State Environmental Protection Key Laboratory of Wetland Ecology and Vegetation Restoration, School of Environment, Northeast Normal University, Changchun, Jilin 130117, China.
(4)Institute of Environmental Research at Greater Bay Area, Key Laboratory for Water Quality and Conservation of the Pearl River Delta, Ministry of Education, Guangzhou University, Guangzhou, 510006, China. Electronic address: [Email]
(5)Center for Environmental and Human Toxicology, Department of Physiological Sciences, College of Veterinary Medicine, UF Genetics Institute, Interdisciplinary Program in Biomedical Sciences Neuroscience, University of Florida, Gainesville, FL 32611, USA. Electronic address: [Email]

Abstract

Strobilurin fungicides are used globally and have been detected in microgram per liter concentrations in aquatic environments. Here, we determined the potential toxicity of four commonly used strobilurins (azoxystrobin, kresoxim-methyl, pyraclostrobin, trifloxystrobin) on mitochondrial function and locomotor activity of larval zebrafish at an environmentally relevant level. As the mode of action of strobilurins in fungi is binding to cytochrome bc1 in mitochondrial complex III, we evaluated exposure effects on mitochondrial oxidative phosphorylation of zebrafish, by measuring oxygen consumption rates, mitochondria-related enzyme activities, and transcripts levels for genes associated with the electron transfer chain and citric acid cycle. We found that 50 nM pyraclostrobin and trifloxystrobin lowered basal respiration, oligomycin-induced ATP respiration, and maximal respiration of embryos. Dysfunction in mitochondrial bioenergetics was associated with changes in mitochondrial complex III activity and transcripts of oxidative respiration and stress-related genes. Lower activity of complex III, and reduced cytb mRNA levels were hypothesized to contribute to reduced electron supply to complex IV and V. Both coxI and atp6 were up-regulated, suggesting a compensatory response to impaired oxidative respiration. Cluster analysis indicated that strobilurin-induced oxidative stress and cytb transcript were related to impaired oxidative phosphorylation. We also assessed larval behavior responses, as reduced ATP can affect activity. We observed that pyraclostrobin and trifloxystrobin induced hypoactive responses in zebrafish. At 50 nM, azoxystrobin and kresoxim-methyl exerted no effects on mitochondrial function nor locomotion of zebrafish. Studies such as this are important for determining sublethal toxicity to these fungicides, as widespread detection of strobilurins in aquatic environments suggests there is a potential for adverse effects in aquatic organisms.