Genomic detection of domoic acid biosynthesis uncovers expanded toxigenic diversity across Pseudo-nitzschia diatoms

Genomic and transcriptomic analyses show the domoic acid biosynthesis (dab) gene cluster is present only in Pseudo-nitzschia species with confirmed DA production, despite widespread environmental dab expression.

• Why it matters: DA risk is hard to predict because toxin production varies among morphologically similar, cryptic lineages, and morphology or single markers often cannot resolve toxigenic potential.
• What they did: The study generated and compiled high-quality Pseudo-nitzschia genomes to build a genus-wide phylogenomic framework, then used metatranscriptomics and nutrient limitation experiments with transcriptional profiling and nontargeted metabolomics.
• The result: The dab cluster shows conserved core structure but ongoing evolution (intronization, locus rearrangement, pseudogenization), including dabC relocation in toxigenic P. australis, and silicon limitation in P. pseudodelicatissima links coordinated dab expression to DA accumulation.