title: "Glucose and ethanol-dependent transcriptional regulation of the astaxanthin biosynthesis pathway in Xanthophyllomyces dendrorhous".
abstract: BACKGROUND
  The yeast Xanthophyllomyces dendrorhous is one of the most promising and economically attractive natural sources of astaxanthin. The biosynthesis of this valuable carotenoid is a complex process for which the regulatory mechanisms remain mostly unknown. Several studies have shown a strong correlation between the carbon source present in the medium and the amount of pigments synthesized. Carotenoid production is especially low when high glucose concentrations are used in the medium, while a significant increase is observed with non-fermentable carbon sources. However, the molecular basis of this phenomenon has not been established.
  
  
  RESULTS
  In this work, we showed that glucose caused transcriptional repression of the three genes involved in the synthesis of astaxanthin from geranylgeranyl pyrophosphate in X. dendrorhous, which correlates with a complete inhibition of pigment synthesis. Strikingly, this regulatory response was completely altered in mutant strains that are incapable of synthesizing astaxanthin. However, we found that addition of ethanol caused the induction of crtYB and crtS gene expression and promoted de novo synthesis of carotenoids. The induction of carotenogenesis was noticeable as early as 24 h after ethanol addition.
  
  
  CONCLUSIONS
  For the first time, we demonstrated that carbon source-dependent regulation of astaxanthin biosynthesis in X. dendrorhous involves changes at the transcriptional level. Such regulatory mechanism provides an explanation for the strong and early inhibitory effect of glucose on the biosynthesis of this carotenoid.
authors.affiliation: Departamento de Ciencias Ecológicas y Centro de Biotecnología, Facultad de Ciencias, Universidad de Chile, Las Palmeras 3425, Ñuñoa, Santiago 7800024, Chile.
authors.forename: Andrés
authors.initials: A
authors.lastname: Marcoleta
authors.forename: Mauricio
authors.initials: M
authors.lastname: Niklitschek
authors.forename: Aniela
authors.initials: A
authors.lastname: Wozniak
authors.forename: Carla
authors.initials: C
authors.lastname: Lozano
authors.forename: Jennifer
authors.initials: J
authors.lastname: Alcaíno
authors.forename: Marcelo
authors.initials: M
authors.lastname: Baeza
authors.forename: Víctor
authors.initials: V
authors.lastname: Cifuentes
mesh_terms: D000431:Ethanol / Q000378:metabolism*; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism; D015966:Gene Expression Regulation, Fungal; D005947:Glucose / Q000378:metabolism*; D014158:Transcription, Genetic; D024341:Xanthophylls / Q000096:biosynthesis; D015003:Yeasts / Q000235:genetics / Q000378:metabolism*
chemical_list: D005656:Fungal Proteins; D024341:Xanthophylls; D000431:Ethanol; C005948:astaxanthine; D005947:Glucose