Transcriptomic analysis of Raphidocelis subcapitata exposed to erythromycin: The role of DNA replication in hormesis and growth inhibition

The occurrence of hormesis in the algal growth inhibition test is a major challenge in the dose-response char-acterization, whereas the molecular mechanism remains unraveled. The aim of this study is therefore to investigate the changes in the molecular pathways in a model green alga Raphidocelis subcapitata treated with erythromycin (ERY; 4, 80, 120 mu g L-1) by transcriptomic analysis. After 7 day exposure, ERY at 4 mu g L-1 caused hormetic effects (21.9 %) on cell density, whereas 52.0 % and 65.4 % were inhibited in two higher exposures. By using adj p 0.05 and absolute log2 fold change 1 as a cutoff, we identified 218, 950, and 2896 differentially expressed genes in 4, 80, 120 mu g L-1 treatment groups, respectively. In two higher ERY treated groups, genes involved in phases I, II & III metabolism processes and porphyrin and chlorophyll metabolism pathway were consistently suppressed. Interestingly, genes (e.g., pri2, mcm2, and mcm6) enriched in DNA replication process were up-regulated in 4 mu g L-1 group, whereas these genes were all repressed in 120 mu g L-1 group. Alteration trend in gene expression was consistent with algal growth. Taken together, our results unveiled the molecular mechanism of action in ERYstimulated/ inhibited growth in green alga.

Automated summary

This study uncovered the hormetic effects of erythromycin on green algal growth and the changes in molecular mechanisms at different concentrations. Transcriptomic analysis revealed distinct alterations in gene expression under different concentrations, affecting the growth of algae.