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Molecular Genetics and Genomics

, Volume 266, Issue 6, pp 914–921 | Cite as

Mutants of the carotene cyclase domain of al-2 from Neurospora crassa

  •  N. Arrach
  •  T. Schmidhauser
  •  J. Avalos
Original Paper

Abstract.

Phytoene synthase and carotene cyclase, two key enzymes in carotenoid biosynthesis, are encoded by two separate genes in bacteria and plants, but by a single bifunctional gene in fungi. The cyclase function has been demonstrated for the products of the genes crtYB from the basidiomycete Xanthophyllomyces dendrorhous, and for carRA and carRP from the zygomycetes Phycomyces blakesleeanus and Mucor circinelloides, respectively. These three genes are highly similar to al-2 from Neurospora crassa. Taking advantage of the high proportion of the final product of the carotenoid pathway that accumulates Neurospora when mycelium is illuminated at low temperature, we have isolated two mutants with a pale reddish pigmentation. Both mutants are complemented by the wild-type al-2 gene, and carry mutations in the al-2 domain to which cyclase activity has been attributed in other fungi. The mutants lack neurosporaxanthin and accumulate an unidentified reddish carotenoid, as shown by column chromatography and HPLC. The chemical and spectrophotometrical properties of this carotenoid are consistent with the absence of carotenoid cyclization, and indicate that the product of al-2 is bifunctional. The existence of a single gene responsible for phytoene synthase and carotene cyclase thus seems to be a widespread trait among filamentous fungi, as shown by the examples now known in a basidiomycete, two zygomycetes and one ascomycete.

Neurospora Carotenoid biosynthesis Al-2 Phytoene synthase Cyclase 

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Copyright information

© Springer-Verlag 2002

Authors and Affiliations

  •  N. Arrach
    • 1
  •  T. Schmidhauser
    • 2
  •  J. Avalos
    • 1
  1. 1.Departamento de Genética, Universidad de Sevilla, Apartado 1095, 41080 Sevilla, Spain
  2. 2.Department of Biology, University of Louisiana, Lafayette, LA 70504, USA

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