Jennifer Alcaino
Universidad de Chile
Title: Genetic control and regulation of the biosynthesis of isoprenoids in the red yeast Xanthophyllomyces dendrorhous
Biography
Biography: Jennifer Alcaino
Abstract
Isoprenoids are natural compounds fulfi lling diverse biological roles. Th ey are structurally conformed by isoprene units,
being isopentenyl-pyrophosphate (IPP) the active form that is synthesized by the mevalonate pathway in non-photosynthetic
organisms. Carotenoids and sterols derive from IPP, being astaxanthin and ergosterol the fi nal products of both biosynthetic
pathways in the red yeast Xanthophyllomyces dendrorhous. Th ese products are biotechnologically attractive because astaxanthin
has antioxidant properties and is used as colorant, while ergosterol is precursor of vitamin D. Th us, the main goal of our group is
to study common genetic elements involved in control and regulation of the synthesis of carotenoids and ergosterol. According
to our results, X. dendrorhous mutants unable to synthesize ergosterol overproduce carotenoids and other sterols, suggesting
that ergosterol regulates its own synthesis by a negative feedback mechanism aff ecting the overall synthesis of isoprenoids in
this yeast. Sterol regulatory element binding proteins (SREBPs) are a family of membrane-bound transcription factors that are
activated by proteolytic cleavage depending on sterol levels to release the N-terminal domain that activates the transcription of
the target genes. SREBPs have been identifi ed in fungi, named as Sre1, being Sre1N the active form. Our studies indicate that
X. dendrorhous has an orthologous sterol-regulated SREBP activation pathway that regulates sterol and carotenoid biosynthesis
as the production of both is aff ected in sre1- mutants. Moreover, the expression of only the Sre1N domain, increases sterol and
carotenoid production, suggesting that Sre1 is responsible for the carotenoid and sterol overproducing phenotype in mutants
unable to produce ergosterol.