Molecular and physiological responses of diatoms to variable levels of irradiance and nitrogen availability: Growth of Skeletonema costatum in simulated upwelling conditions

• DOI: 10.4319/lo.1992.37.5.0989
• Publication Date: 2010-04-16T19:32:59Z
• Authors: G. Jason Smith; Richard C. Zimmerman; Randall S. Alberte
• Keywords: Assimilation (phonology); Nitrogen Assimilation

Molecular mechanisms that drive metabolic acclimation to environmental shifts have been poorly characterized in phytoplankton. In this laboratory study, the response of light- and N-limited Skeletonema costatum cells an increase light NO3 availability was examined. C assimilation depressed relative N early enrichment, photosynthetic quotient (O2 : CO2) increased, consistent with shunting reducing equivalents from CO2 fixation NO3− reduction. The concomitant dark respiration increased energetic demand associated macromolecular synthesis. accelerations N-specific rates uptake nitrate reductase activity (NRA) over first 24 h were comparable observations for coastal upwelling systems. Increases cell-specific these processes, however, confined 8 enrichment. abundance 18S ribosomal ribonucleic acid (rRNA) immediately after shift, followed by increases levels NR-specific mRNA coincided acceleration assimilation. NRA, exhibited a diurnal rhythm did not correspond changes NR protein abundance, suggesting enzyme also regulated direct modulation existing availability.