tailieunhanh - Báo cáo khoa học: Deviation of the neurosporaxanthin pathway towards b-carotene biosynthesis in Fusarium fujikuroi by a point mutation in the phytoene desaturase gene

Carotenoids are widespread terpenoid pigments with applications in the food and feed industries. Upon illumination, the gibberellin-producing fun-gusFusarium fujikuroi(Gibberella fujikuroimating population C) develops an orange pigmentation caused by an accumulation of the carboxylic apoc-arotenoid neurosporaxanthin. | ễFEBS Journal Deviation of the neurosporaxanthin pathway towards b-carotene biosynthesis in Fusarium fujikuroi by a point mutation in the phytoene desaturase gene Alfonso Prado-Cabrero1 Patrick Schaub2 Violeta Diaz-Sanchez1 Alejandro F. Estrada1 Salim Al-Babili2 and Javier Avalos1 1 Departamento de Genetica Universidad de Sevilla Spain 2 Albert-Ludwigs University of Freiburg Faculty of Biology Germany Keywords carB carotenogenesis carotenoid overproducing mutant filamentous fungi PDS enzyme Correspondence J. Avalos Departamento de Genetica Universidad de Sevilla Apartado 1095 E-41080 Sevilla Spain Fax 34 95 455 7104 Tel 34 95 455 7110 E-mail avalos@ Received 12 May 2009 revised 12 June 2009 accepted 22 June 2009 doi Carotenoids are widespread terpenoid pigments with applications in the food and feed industries. Upon illumination the gibberellin-producing fungus Fusarium fujikuroi Gibberella fujikuroi mating population C develops an orange pigmentation caused by an accumulation of the carboxylic apocarotenoid neurosporaxanthin. The synthesis of this xanthophyll includes five desaturation steps presumed to be catalysed by the carB-encoded phytoene desaturase. In this study we identified a yellow mutant SF21 by mutagenesis of a carotenoid-overproducing strain. HPLC analyses indicated a specific impairment in the ability of SF21-CarB to perform the fifth desaturation as implied by the accumulation of y-carotene and b-carotene which arise through four-step desaturation. Sequencing of the SF21 carB allele revealed a single mutation resulting in an exchange of a residue conserved in other five-step desaturases. Targeted carB allele replacement proved that this single mutation is the cause of the SF21 carotenoid pattern. In support expression of SF21 CarB in engineered carotene-producing Escherichia coli strains demonstrated its reduced ability to catalyse the fifth desaturation step on both monocyclic and acyclic substrates. Further .