Transcriptome-wide deregulation of gene expression by artificial light at night in tadpoles of common toads

Nov 22, 2021The Science of the total environment

Artificial Light at Night Alters Gene Activity Across the Whole Genome in Common Toad Tadpoles

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Abstract

Artificial light at night (ALAN) affected 11.2% of gene expression in Bufo bufo tadpoles exposed to 5 lx during the day.

ALAN influenced gene expression both at night and during the day, with 3.5% to 11% of genes being differentially expressed at night depending on light intensity.
A higher percentage of genes were downregulated in response to ALAN, with 58% and 62% downregulated at night at 0.1 and 5 lx, respectively, and 61.2% downregulated during the day at 5 lx.
Effects of ALAN were observed even at very low light levels (0.1 lx).
The majority of affected genes were associated with the innate immune system, indicating potential impacts on immune capacity.
The study highlights the significance of investigating gene expression changes during both day and night in the context of ALAN.

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Artificial light at night (ALAN) affects numerous physiological and behavioural mechanisms in various species by potentially disturbing circadian timekeeping systems and modifying melatonin levels. However, given the multiple direct and indirect effects of ALAN on organisms, large-scale transcriptomic approaches are essential to assess the global effect of ALAN on biological processes. Moreover, although studies have focused mainly on variations in gene expression during the night in the presence of ALAN, it is necessary to investigate the effect of ALAN on gene expression during the day. In this study, we combined de novo transcriptome sequencing and assembly, and a controlled laboratory experiment to evaluate the transcriptome-wide gene expression response using high-throughput (RNA-seq) in Bufo bufo tadpoles exposed to ecologically relevant light levels. Here, we demonstrated for the first time that ALAN affected gene expression at night (3.5% and 11% of differentially expressed genes when exposed to 0.1 and 5 lx compared to controls, respectively), but also during the day (11.2% of differentially expressed genes when exposed to 5 lx compared to controls) with a dose-dependent effect. ALAN globally induced a downregulation of genes (during the night, 58% and 62% of the genes were downregulated when exposed to 0.1 and 5 lx compared to controls, respectively, and during the day, 61.2% of the genes were downregulated when exposed to 5 lx compared to controls). ALAN effects were detected at very low levels of illuminance (0.1 lx) and affected mainly genes related to the innate immune system and, to a lesser extend to lipid metabolism. These results provide new insights into understanding the effects of ALAN on organism. ALAN impacted the expression of genes linked to a broad range of physiological pathways at very low levels of ALAN during night-time and during daytime, potentially resulting in reduced immune capacity under environmental immune challenges.

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Transcriptome-wide deregulation of gene expression by artificial light at night in tadpoles of common toads

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