Nitrogen starvation promotes production of the β-N-methylamino-L-alanine-containing proteins in marine diatoms.

The neurotoxin β-N-methylamino-L-alanine (BMAA) produced by marine diatoms has been implicated in some neurological disorders, and there is a need to elucidate the biological processes involved in the production of BMAA-containing proteins. In this study, growth of seven diatoms was suppressed under nitrogen limitation, however the production of BMAA-containing proteins was significantly increased in six of them, up to 5.22-fold increase in Thalassiosira andamanica. These variations were associated with reduced concentration of dissolved inorganic nitrogen (DIN) and changes in photosynthetic efficiency. Analytical results of non-targeted metabolomics showed that the obvious changes in amino acids, lipids and sugars may help diatoms to adjust growth and physiological parameters. Combined with previous transcriptomic data, a decrease in N-acetyl-D-glucosamine (GlcNAc) leads to an increase in N-glycan terminal modifications, which in turn increases protein misfolding. In addition, the reduced efficiency of vesicular transport in the COPII system may have exacerbated the accumulation of BMAA-containing proteins.