title: Regulation of carotenoid biosynthetic genes expression and carotenoid accumulation in the green alga Haematococcus pluvialis under nutrient stress conditions.
abstract: Haematococcus pluvialis, a green alga, accumulates carotenoids, predominantly astaxanthin, when exposed to stress conditions. In the present work, changes in the pigment profile and expression of carotenogenic genes under various nutrient stress conditions and their regulation were studied. Nutrient stress and higher light intensity in combination with NaCl/sodium acetate (SA) enhanced total carotenoid and total astaxanthin content to 32.0 and 24.5 mg g(-1) of dry biomass, respectively. Expression of carotenogenic genes, phytoene synthase (PSY), phytoene desaturase (PDS), lycopene cyclase (LCY), beta-carotene ketolase (BKT), and beta-carotene hydroxylase (CHY) were up-regulated under all the stress conditions studied. However, the extent of expression of carotenogenic genes varied with stress conditions. Nutrient stress and high light intensity induced expression of astaxanthin biosynthetic genes, BKT and CHY, transiently. Enhanced expression of these genes was observed with SA and NaCl/SA, while expression was delayed with NaCl. The maximum content of astaxanthin recorded in cells grown in medium with SA and NaCl/SA correlated with the expression profile of the astaxanthin biosynthetic genes. Studies using various inhibitors indicated that general carotenogenesis and secondary carotenoid induction were regulated at both the transcriptional and the cytoplasmic translational levels. The induction of general carotenoid synthesis genes was independent of cytoplasmic protein synthesis while BKT gene expression was dependent on de novo protein synthesis.
authors.affiliation: Plant Cell Biotechnology Department, Central Food Technological Research Institute, Mysore-570 020, India.
authors.forename: Raman
authors.initials: R
authors.lastname: Vidhyavathi
authors.forename: Lakshmanan
authors.initials: L
authors.lastname: Venkatachalam
authors.forename: Ravi
authors.initials: R
authors.lastname: Sarada
authors.forename: Gokare Aswathanarayana
authors.initials: GA
authors.lastname: Ravishankar
mesh_terms: D019883:Alkyl and Aryl Transferases / Q000037:antagonists & inhibitors / Q000235:genetics; D018533:Biomass; D053898:Biosynthetic Pathways / Q000187:drug effects / Q000235:genetics; D002338:Carotenoids / Q000235:genetics* / Q000378:metabolism*; D000460:Chlorophyta / Q000187:drug effects / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D015870:Gene Expression / Q000187:drug effects; D020869:Gene Expression Profiling; D051232:Geranylgeranyl-Diphosphate Geranylgeranyltransferase; D019753:Intramolecular Lyases / Q000037:antagonists & inhibitors / Q000235:genetics; D008027:Light; D006899:Mixed Function Oxygenases / Q000037:antagonists & inhibitors / Q000235:genetics; D019384:Nucleic Acid Synthesis Inhibitors / Q000494:pharmacology; D010088:Oxidoreductases / Q000037:antagonists & inhibitors / Q000235:genetics; D010860:Pigments, Biological / Q000378:metabolism; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D048030:RNA, Algal / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D019384:Nucleic Acid Synthesis Inhibitors; D010860:Pigments, Biological; D011500:Protein Synthesis Inhibitors; D048030:RNA, Algal; D002338:Carotenoids; D006899:Mixed Function Oxygenases; D010088:Oxidoreductases; C022398:phytoene dehydrogenase; D019883:Alkyl and Aryl Transferases; D051232:Geranylgeranyl-Diphosphate Geranylgeranyltransferase; D019753:Intramolecular Lyases; C070925:lycopene cyclase-isomerase