RESUMO
In the yeast Xanthophyllomyces dendrorhous the genes idi, crtE, crtYB, crtl and ast are involved in the biosynthesis of astaxanthin from isopentenyl pyrophosphate. The carotenoid production and the kinetics of mRNA expression of structural genes controlling the carotenogenesis in a wild-type ATCC 24230 and in carotenoid overproducer deregulated atxS2 strains were studied. The biosynthesis of carotenoid was induced at the late exponential growth phase in both strains. However, the cellular carotenoid concentration was four times higher in atxS2 than in the wild-type strain in the exponential growth phase, suggesting that carotenogenesis was deregulated in atxS2 at the beginning of growth. In addition, the maximum expression of the carotenogenesis genes at the mRNA level was observed during the induction period of carotenoid biosynthesis in the wild-type strain. The mRNA level of the crtYB, crtl, ast genes and to a lesser extent the idi gene, decayed at the end of the exponential growth phase. The mRNA levels of the crtE gene remained high along the whole growth curve of the yeast. In the atxS2 strain the mRNA levels of crtE gene were about two times higher than the wild-type strain in the early phase of the growth cycle.
Assuntos
Basidiomycota/genética , Carotenoides/genética , Regulação Fúngica da Expressão Gênica , Basidiomycota/metabolismo , Carotenoides/biossíntese , Meios de Cultura , RNA Fúngico/genética , RNA Mensageiro/genética , Reação em Cadeia da Polimerase Via Transcriptase Reversa , XantofilasRESUMO
In the yeast Xanthophyllomyces dendrorhous the genes idi, crtE, crtYB, crtl and ast are involved in the biosynthesis of astaxanthin from isopentenyl pyrophosphate. The carotenoid production and the kinetics of mRNA expression of structural genes controlling the carotenogenesis in a wild-type ATCC 24230 and in carotenoid overproducer deregulated atxS2 strains were studied. The biosynthesis of carotenoid was induced at the late exponential growth phase in both strains. However, the cellular carotenoid concentration was four times higher in atxS2 than in the wild-type strain in the exponential growth phase, suggesting that carotenogenesis was deregulated in atxS2 at the beginning of growth. In addition, the maximum expression of the carotenogenesis genes at the mRNA level was observed during the induction period of carotenoid biosynthesis in the wild-type strain. The mRNA level of the crtYB, crtl, ast genes and to a lesser extent the idi gene, decayed at the end of the exponential growth phase. The mRNA levels of the crtE gene remained high along the whole growth curve of the yeast. In the atxS2 strain the mRNA levels of crtE gene were about two times higher than the wild-type strain in the early phase of the growth cycle.
Assuntos
Basidiomycota/genética , Carotenoides/genética , Regulação Fúngica da Expressão Gênica , Basidiomycota/metabolismo , Meios de Cultura , Carotenoides/biossíntese , Reação em Cadeia da Polimerase Via Transcriptase Reversa , RNA Fúngico/genética , RNA Mensageiro/genética , XantofilasRESUMO
Xanthophyllomyces dendrorhous is one of the relevant sources of the carotenoid astaxanthin. In this paper, we describe for the first time cloning of unexpected cDNAs obtained from the crtI and crtYB genes of X. dendrorhous strain UCD 67-385. The cDNA of the crtI gene conserves 80 bp of the first intron, while the cDNA of the crtYB gene conserves 55 bp of the first intron and lacks 111 bp of the second exon. The crtI and crtYB RNAs could be spliced in alternative splice sites, which produced alternative transcripts which could not be translated to active CRTI and CRTYB proteins since they had numerous stop codons in their sequences. The ratio of mature mRNA to alternative mRNA for the crtI gene decreased as a function of the age of the culture, while the cellular content of carotenoids increased. It is possible that splicing to mature or alternative transcripts could regulate the cellular concentrations of phytoene desaturase and phytoene synthase-lycopene cyclase proteins, depending on the physiological or environmental conditions.