Transcriptional Responses of the Marine Planktonic Diatom Chaetoceros tenuissimus to Nitrogen- and Phosphorus-deficient States

Dissolved nutrients, especially inorganic nitrogen (N) and inorganic phosphorus (P), are typically deficient in the coastal surface waters of temperate regions during warm seasons. Even under the conditions of inorganic N and P deficiencies, the planktonic diatom Chaetoceros tenuissimus sometimes forms blooms. The present study characterized, at the mRNA transcript level, the gene expression patterns in N- or P-limited cultures of C. tenuissimus to propose the molecular markers of N- and P-deficient states of C. tenuissimus. Gene transcriptions of nitrate transporter and glutamine synthetase appeared to be upregulated in N-limited cultures. Phosphate transporter and alkaline phosphatase transcriptions appeared to be induced under P-limited conditions. These results suggest that C. tenuissimus under the N-deficient state expresses a transmembrane nitrate transporter, uptakes nitrate effectively, and assimilates the N source rapidly via glutamine synthesis; P-deficient C. tenuissimus possibly supplements P sources from organic P compounds via hydrolysis actions of phosphatases and uptakes phosphate effectively through phosphate transporters.