The response of Chlamydomonas reinhardtii to nitrogen deprivation: a systems biology analysis

Citations Over TimeTop 10% of 2014 papers

Abstract

Drastic alteration in macronutrients causes large changes in gene expression in the photosynthetic unicellular alga Chlamydomonas reinhardtii. Preliminary data suggested that cells follow a biphasic response to this change hinging on the initiation of lipid accumulation, and we hypothesized that drastic repatterning of metabolism also followed this biphasic modality. To test this hypothesis, transcriptomic, proteomic, and metabolite changes that occur under nitrogen (N) deprivation were analyzed. Eight sampling times were selected covering the progressive slowing of growth and induction of oil synthesis between 4 and 6 h after N deprivation. Results of the combined, systems-level investigation indicated that C. reinhardtii cells sense and respond on a large scale within 30 min to a switch to N-deprived conditions turning on a largely gluconeogenic metabolic state, which then transitions to a glycolytic stage between 4 and 6 h after N depletion. This nitrogen-sensing system is transduced to carbon- and nitrogen-responsive pathways, leading to down-regulation of carbon assimilation and chlorophyll biosynthesis, and an increase in nitrogen metabolism and lipid biosynthesis. For example, the expression of nearly all the enzymes for assimilating nitrogen from ammonium, nitrate, nitrite, urea, formamide/acetamide, purines, pyrimidines, polyamines, amino acids and proteins increased significantly. Although arginine biosynthesis enzymes were also rapidly up-regulated, arginine pool size changes and isotopic labeling results indicated no increased flux through this pathway.

Related Papers

• → Humic substances stimulate maize nitrogen assimilation and amino acid metabolism at physiological and molecular level(2015)83 cited
• → Five nitrate assimilation-related loci are clustered in Chlamydomonas reinhardtii(1993)89 cited
• → Effect of Nitrate, Ammonium and Glutamine on Nitrogen Assimilation Enzymes during Callus Growth of Maize(1986)11 cited
• → Nitrogen assimilation and metabolism in rusted leek leaves(1988)8 cited
• → Nitrogen assimilation and regulation of nitrate and nitrite reductases in cultured Ipomoea cells(1977)11 cited