Research article

Cloning of the cytochrome p450 reductase (crtR) gene and its involvement in the astaxanthin biosynthesis of Xanthophyllomyces dendrorhous

Jennifer Alcaíno, Salvador Barahona, Marisela Carmona, Carla Lozano, Andrés Marcoleta, Mauricio Niklitschek, Dionisia Sepúlveda, Marcelo Baeza and Víctor Cifuentes^*

• * Corresponding author: Víctor Cifuentes vcifuentes@uchile.cl

Author Affiliations

Departamento de Ciencias Ecológicas, Facultad de Ciencias, Universidad de Chile, Santiago, Chile

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BMC Microbiology 2008, 8:169 doi:10.1186/1471-2180-8-169

Published: 6 October 2008

Abstract

Background

The yeast Xanthophyllomyces dendrorhous synthesizes astaxanthin, a carotenoid with high commercial interest. The proposed biosynthetic route in this organism is isopentenyl-pyrophosphate (IPP) → geranyleranyl pyrophosphate (GGPP) → phytoene → lycopene → β-carotene → astaxanthin. Recently, it has been published that the conversion of β-carotene into astaxanthin requires only one enzyme, astaxanthin synthase or CrtS, encoded by crtS gene. This enzyme belongs to the cytochrome P450 protein family.

Results

In this work, a crtR gene was isolated from X. dendrorhous yeast, which encodes a cytochrome P450 reductase (CPR) that provides CrtS with the necessary electrons for substrate oxygenation. We determined the structural organization of the crtR gene and its location in the yeast electrophoretic karyotype. Two transformants, CBSTr and T13, were obtained by deleting the crtR gene and inserting a hygromycin B resistance cassette. The carotenoid composition of the transformants was altered in relation to the wild type strain. CBSTr forms yellow colonies because it is unable to produce astaxanthin, hence accumulating β-carotene. T13 forms pale colonies because its astaxanthin content is reduced and its β-carotene content is increased.

Conclusion

In addition to the crtS gene, X. dendrorhous requires a novel gene, crtR, for the conversion of β-carotene to astaxanthin.