Grazing-induced cellular responses in toxic diatom Pseudo-nitzschia multiseries

Blooms of Pseudo-nitzschia are frequent in coastal areas, and many species have been confirmed to synthesize the neurotoxin domoic acid (DA). DA accumulates in filter-feeding marine organisms, posing a threat to human health. Grazing on Pseudo-nitzschia is considered a factor that affects the production of DA. There is a substantial body of literature focusing on the biotic and abiotic factors that influence DA accumulation, while the detailed molecular processes within the algal cells remain largely unexplored. Using co-culture of Pseudo-nitzschia multiseries and Artemia salina nauplii, we integrated multi-omics and physiological analyses to investigate the defense mechanisms of P. multiseries against grazing. The data revealed increased levels of secondary metabolites such as DA (0.20 pg/cell/day) and jasmonic acid (1.88-fold increase, by metabolomics), decreased metabolic efficiency, enhanced photosynthetic efficiency, and reduced cell growth rates. These observations suggest that algal cells respond to grazing by modulating their biochemical composition and energy metabolism pathways. Our findings provide a molecular basis for the resistance of toxic diatoms to grazing pressure.