Transcriptomic signaling in zebrafish (Danio rerio) embryos exposed to environmental concentrations of glyphosate

Abstract

Glyphosate [N-(phosphonomethyl)glycine] is one of the most popular herbicides worldwide. Globally, the use of glyphosate is increasing, and its residues have been found in drinking water and food products. The data regarding the possible toxic effects of this herbicide are controversial. Therefore, the aim of this study was to evaluate the effects of glyphosate at environmental concentrations in zebrafish (Danio rerio) embryos. Embryos were exposed to 0, 1, 100, and 1,000 µg/L glyphosate for 96 h, and mortality, heart rate, and hatching rate were evaluated. After the experiment, RNA was extracted from the embryos for transcriptional analysis. No mortality was recorded, and exposure to 100 µg/L and 1,000 µg/L of glyphosate resulted in lower heart rates at 48 h. In addition, RNA-seq analysis revealed that glyphosate exposure induced subtle changes in gene transcription profiles. We found 30 differentially expressed genes; however, the highest glyphosate concentration (1,000 µg/L) induced the greatest number of differentially expressed genes involved in oocyte maturation, metabolic processes, histone deacetylation, and nervous system development.

Keywords:

• Glyphosate
• toxicity
• development
• transcriptomic
• zebrafish

Acknowledgments

We thank Irma Eugenia Martínez Rodriguez and Gabriela Aguilar Zárate for their support and technical assistance. We thank Andrea Lievana MacTavish for English language editing. We also thank Pedro Bastidas for the analysis of glyphosate in water.

Ethical approval

According to the EU Directive 2010/63/EU on the protection of animals used for scientific purposes, early life-stages of zebrafish are not protected as animals until the stage of being capable of independent feeding (5 days post fertilization),^[72] therefore for 96 hpf embryos, an Ethical Approval is not required. Nevertheless, we are concerned of animal welfare at any stage of development and followed the Mexican guidelines for animal experimentation (NOM-033-SAG/ZOO-2014), as well as the British guidelines for fish welfare reported by Ashley.^[73]

Additional information

Funding

Partial funding for this study was provided by the National Council for Science and Technology (CONACYT) project (CB2016-288306) and PhD grant to LTS ( #CVU695082).