3.2 Molecular responses of A. erythraea and its gut microbiota on a DA diet
To find the potential detoxification mechanisms associated with the DA diet, a metatranscriptome analysis was conducted. We analyzed the results of A. erythraea and gut microbiota separately. A total of 844 million raw reads were generated, resulting in 752 million clean reads. Among these, the average proportion of sequences mapped toA. erythraea was 26.69%, the average proportion mapped to gut microbiota was 8.62%, and the detailed proportions for each sample are provided in Table S2.
A. erythraea fed with toxic and non-toxic diets exhibited distinct gene expression profiles (Fig. S3A). Through KEGG enrichment analysis, we found that pathways involved in ingestion, such as protein digestion and absorption (map04974) and lysosome (map04142), were significantly downregulated on the toxic diet (Table S3). This finding is consistent with the observed reduction in grazing by A. erythraea on the toxic diet (Fig. 2A).Additionally , we found that processes related to cell death and cell proliferation were significantly upregulated on the toxic diet (Table S3), which was further supported by stronger TUNEL and EdU signals observed in the toxic diet (Fig. S4). This suggests that A. erythraea may accelerate cell proliferation to repair damaged cells and mitigate the adverse effects of DA.
We then examined the gene expression profiles of gut bacteria. Similar to copepods, the PCA plot revealed that the toxic and non-toxic diets clustered into distinct groups (Fig. 3A), indicating the different expression profiles between the two. Compared to the non-toxic group,A. erythraea exhibited 9,867 DEGs on the first day (7,329 upregulated and 2,538 downregulated) and 23,871 DEGs on the second day (13,757 upregulated and 10,114 downregulated) (Fig. 3B). To further investigate, we conducted KEGG enrichment analysis on these DEGs to identify key pathways activated by DA diet. In this context , metabolism is the primary process involved in microbial detoxification and adaptation to toxicity. Consequently , we concentrated on the metabolic pathways that were significantly enriched (adjusted p -value < 0.05). Eight metabolic pathways were significantly upregulated on the first day, and twelve on the second day (Fig. 3C; Table S4).