Global gene expression in recombinant and non-recombinant yeast Saccharomyces cerevisiae in three different metabolic states
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Dáz, H.
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Global gene expression in recombinant and non-recombinant yeast Saccharomyces cerevisiae in three different metabolic states
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Abstract
Global gene expression of two strains of Saccharomyces cerevisiae, one recombinant (P+), accumulating large
amounts of an intracellular protein Superoxide Dismutase (SOD) and one non-recombinant (P−) which does
not contain the recombinant plasmid, were compared in batch culture during diauxic growth when cells were
growing exponentially on glucose, when they were growing exponentially on ethanol, and in the early
stationary phase when glycerol was being utilized.
When comparing the gene expression for P− (and P+) during growth on ethanol to that on glucose (Eth/
Gluc), overexpression is related to an increase in consumption of glycerol, activation of the TCA cycle,
degradation of glycogen and metabolism of ethanol. Furthermore, 97.6% of genes (80 genes) involved in the
central metabolic pathway are overexpressed. This is similar to that observed by DeRisi et al. [DeRisi, J.L.,
Iyer, V.R. & Brown, P.O. 1997. Exploring the metabolic and genetic control of gene expression on a genomic
scale. Science 278:680–686.] but very different fromwas observed forMetabolic Flux Analysis (MFA),where
the specific growth rate is lowered to ca. 40%, the fluxes in the TCA cycle are reduced to ca. 40% (to 30% inP+),
glycolysis is reduced to virtually 0 and protein synthesis to ca. 50% (to 40% in P+). Clearly it is not possible to
correlate in a simple or direct way, quantitativemRNA expression levels with cell functionwhich is shown by
the Metabolic Flux Analysis (MFA).
When comparing the two strains in the 3 growth stages, 4 geneswere found to be under or overexpressed in
all cases. The products of all of these genes are expressed at the plasma membrane or cell wall of the yeast.
While comparing the strains (P+/P−) when growing on glucose, ethanol and in the early stationary phase,
many of the genes of the central metabolic pathways are underexpressed in P+, which is similar to the
behaviour of the metabolic fluxes of both strains (MFA). Comparing the gene expression for P−(and to some
extent P+) during the early stationary phase to growth on ethanol (Stat/Eth), underexpression is
generalized. This shows that the switch in metabolism between ethanol and early stationary phases has
an almost instantaneous effect on gene expression but a much more retarded effect on metabolic fluxes and
that the “early stationary” phase represents a “late ethanol” phase fromthe metabolic analysis point of view
since ethanol is still present and being consumed although at a much slower rate.
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URI: https://repositorio.uchile.cl/handle/2250/125936
DOI: DOI:10.1016/j.biotechadv.2009.05.015
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Biotechnology Advances 27 (2009) 1092–1117
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