Metabolic acclimation to excess light intensity in Chlamydomonas reinhardtii.
There are several well-described acclimation responses to excess light in green algae but the effect on metabolism has not been thoroughly investigated. This study examines the metabolic changes during photoacclimation to high-light (HL) stress in Chlamydomonas reinhardtii using nuclear magnetic resonance and mass spectrometry. Using principal component analysis, a clear metabolic response to HL intensity was observed on global metabolite pools, with major changes in the levels of amino acids and related nitrogen metabolites. Amino acid pools increased during short-term photoacclimation, but were especially prominent in HL-acclimated cultures. Unexpectedly, we observed an increase in mitochondrial metabolism through downstream photorespiratory pathways. The expression of two genes encoding key enzymes in the photorespiratory pathway, glycolate dehydrogenase and malate synthase, were highly responsive to the HL stress. We propose that this pathway contributes to metabolite pools involved in nitrogen assimilation and may play a direct role in photoacclimation. Our results suggest that primary and secondary metabolism is highly pliable and plays a critical role in coping with the energetic imbalance during HL exposure and a necessary adjustment to support an increased growth rate that is an effective energy sink for the excess reducing power generated during HL stress.
Department of Biology, University of New Brunswick, Fredericton, NB E3B 5A3, Canada.
Maria C
MC
Davis
Genome Center, University of California Davis, Davis, CA, 95616, USA.
Oliver
O
Fiehn
Department of Biology, University of New Brunswick, Fredericton, NB, Canada, E3B 5A3.
Dion G
DG
Durnford
D000064:Acclimatization; D000429:Alcohol Oxidoreductases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D020418:Algal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D000596:Amino Acids / Q000378:metabolism; D016825:Chlamydomonas reinhardtii / Q000235:genetics / Q000378:metabolism* / Q000528:radiation effects; D008401:Gas Chromatography-Mass Spectrometry; D018506:Gene Expression Regulation, Plant / Q000528:radiation effects; D008027:Light; D008292:Malate Synthase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D013058:Mass Spectrometry; D053858:Metabolic Networks and Pathways / Q000528:radiation effects; D055432:Metabolomics; D008928:Mitochondria / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism; D019906:Nuclear Magnetic Resonance, Biomolecular; D010788:Photosynthesis; D013312:Stress, Physiological
D020418:Algal Proteins; D000596:Amino Acids; D000429:Alcohol Oxidoreductases; C020819:glycolic acid dehydrogenase; D008292:Malate Synthase; D009584:Nitrogen
light stress; metabolomics; photoacclimation; photorespiration