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RESPONSE OF GLUTAMINE SYNTHETASE GENE TRANSCRIPTION AND ENZYME ACTIVITY TO EXTERNAL NITROGEN SOURCES IN THE DIATOM SKELETONEMA COSTATUM (BACILLARIOPHYCEAE) 1
Author(s) -
Takabayashi Misaki,
Wilkerson Frances P.,
Robertson Deborah
Publication year - 2005
Publication title -
journal of phycology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.85
H-Index - 127
eISSN - 1529-8817
pISSN - 0022-3646
DOI - 10.1111/j.1529-8817.2005.04115.x
Subject(s) - glutamine synthetase , biology , ammonium , diatom , enzyme , gene expression , gene , glutamine , isozyme , transcription (linguistics) , biochemistry , phytoplankton , nitrate , botany , microbiology and biotechnology , ecology , nutrient , amino acid , chemistry , linguistics , philosophy , organic chemistry
To understand the enhanced ability of marine diatoms to assimilate nitrogen (N), we measured changes in the transcript abundance and enzyme activity of glutamine synthetase (GS), one of the key enzymes that link carbon (C) and N metabolism, in the common diatom Skeletonema costatum (Greville) Cleve. Transcript abundance of glnII (the gene that encodes the GSII isoenzyme), measured by quantitative reverse transcriptase‐PCR, and total GS activity increased 2 to 3.5 times above background in the cells taking up nitrate (NO 3 − ) but not the cells taking up ammonium (NH 4 + ). A background level of glnII mRNA was maintained at a steady level up to 15 days of N starvation before decreasing to below detection after 21 days. These results confirm that transcription of glnII is induced to assimilate NH 4 + derived from reduction of NO 3 − . Because of this role of GSII in diatoms assimilating NH 4 + derived from NO 3 − reduction rather than from the environmental NH 4 + , quantification of glnII mRNA promises to be a useful indication of new production by phytoplankton.