Distinct m⁶A methylome profiles in poly(A) RNA from Xenopus laevis testis and that treated with atrazine

Recent discovery of reversible N⁶-methyladenosine (m⁶A) methylation on messenger RNA (mRNA) and mapping of m⁶A methylomes in mammals, plant and yeast revealed potential regulatory functions of this RNA modification. However, the role of the m⁶A methylomes in amphibious is still poorly understood. Here, we examined the m⁶A transcriptome-wide profile in testis tissues of Xenopus laevis (X. laevis) with and without treatment with 100 μg/L atrazine (AZ) through m⁶A sequencing analysis using the latest Illumina HiSeq sequencer. The results revealed that m⁶A is a highly conserved modification of mRNA in X. laevis. Distinct from that in mammals, m⁶A in X. laevisis enriched around the stop codon and start codon, as is reported in plant. We then investigated the differential expression m⁶A in testes of AZ-exposed X. laevis and compared that with the X. laevis in the control group by m⁶A sequencing. The results indicated that AZ leads to altered expression profile in 1380 m⁶A modification sites (696 upregulated and 684 downregulated). KEGG pathway analysis indicates that the "NOD-like receptors", "tight junction", "Peroxisome proliferator-activated receptors", "adherens junctions", "Glycerophospholipid metabolism" and "Fatty acid biosynthesis" signaling pathways may be associated with abnormal testis development of X. laevis due to exposure to AZ. Analysis results showed a positive correlation between m⁶A modification and mRNA abundance, suggesting a regulatory role of m⁶A in amphibious gene expression. Our first report of m⁶A transcriptome-wide map of an amphibian species X. laevis presented here provides a starting roadmap for uncovering m⁶A functions that may affect/control amphibian testis development.