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Understanding the Effects of Novel Engineering Targets on Sugar Sensing in S. cerevisiae

Fjölnisdóttir, Birta Líf LU (2018) KMBM01 20181
Applied Microbiology
Biotechnology
Abstract
Baker´s yeast S. cerevisiae has been engineered in order to enable xylose uptake and utilization from lignocellulosic biomass as this yeast cannot naturally metabolize this pentose sugar. However, xylose is not recognized as a fermentable sugar by S. cerevisiae and recent studies on the effect of xylose on the three main sugar signaling pathways (Snf3p/Rgt2p, SNF1/Mig1pt and cAMP/PKA) have indicated that S. cerevisiae cannot sense extracellular xylose. In parallel, it was recently shown that the combined deletions of HOG1, IRA2, GRE3 and ISU2 gave epistatic interactions resulting in improved growth and xylose uptake in recombinant S. cerevisiae strains containing the XI pathway. The objective of the present study was to explore the effects... (More)
Baker´s yeast S. cerevisiae has been engineered in order to enable xylose uptake and utilization from lignocellulosic biomass as this yeast cannot naturally metabolize this pentose sugar. However, xylose is not recognized as a fermentable sugar by S. cerevisiae and recent studies on the effect of xylose on the three main sugar signaling pathways (Snf3p/Rgt2p, SNF1/Mig1pt and cAMP/PKA) have indicated that S. cerevisiae cannot sense extracellular xylose. In parallel, it was recently shown that the combined deletions of HOG1, IRA2, GRE3 and ISU2 gave epistatic interactions resulting in improved growth and xylose uptake in recombinant S. cerevisiae strains containing the XI pathway. The objective of the present study was to explore the effects of those gene deletions on sensing and signaling for the three sugar signaling pathways. Deletions of IRA2, ISU1 and HOG1 were constructed in S. cerevisiae strains containing the XR-XDH pathway as well as a biosensor for each of the signaling pathways and the response was recorded using flow cytometry. Results confirmed clear effects of the deletions on all the signaling pathways, with ira2Δ mutants mimicking high glucose signal with constitutive activation of PKA and hog1Δ mutants giving low glucose responses. When combined with the deletion of ISU1, the SNF1/Mig1p pathway was clearly affected since subpopulations were alleviated. (Less)
Popular Abstract
Can genetic modifications affect the three main sugar signaling pathways of baker´s yeast? Is it possible that sugar sensing is fundamental for the improvement of xylose utilization by yeast?

The need for sustainable production of goods has led to an increased interest for the use of renewable raw materials such as biomass coming from wood or agricultural wastes. Microorganisms have proven to be extremely helpful in the utilization of the sugars present in biomass, for the production of valuable compounds such as biofuels and bioplastics. However, since very few of them can withstand the heavy pretreatment required to access the sugars present in biomass, baker’s yeast also called Saccharomyces cerevisiae, has been considered as the... (More)
Can genetic modifications affect the three main sugar signaling pathways of baker´s yeast? Is it possible that sugar sensing is fundamental for the improvement of xylose utilization by yeast?

The need for sustainable production of goods has led to an increased interest for the use of renewable raw materials such as biomass coming from wood or agricultural wastes. Microorganisms have proven to be extremely helpful in the utilization of the sugars present in biomass, for the production of valuable compounds such as biofuels and bioplastics. However, since very few of them can withstand the heavy pretreatment required to access the sugars present in biomass, baker’s yeast also called Saccharomyces cerevisiae, has been considered as the best good candidate due to its robustness, tolerance to extreme conditions as well as to toxic compounds and the fact that its well studied within the scientific community.

One drawback however is that yeast cannot naturally metabolize xylose that is the second most abundant sugar in nature after glucose. Therefore extensive studies have been performed in order to enable and improve xylose utilization in yeast; but so far, the efficiency is still not comparable to glucose. Recent findings have indicated that yeast does not “sense" xylose outside of the cell, a mechanism that is essential in order to transport the sugar into the cell and induce its utilisation. Another study has also led to the identification of proteins whose inactivation improves xylose utilization; although the mechanism of action is unclear, it is possible that these proteins affect the sensing of xylose.

In the present study, genes corresponding to the proteins discussed above were deleted in yeast strains that had been engineered to use xylose and contained a biosensor that enables monitoring the activation of the various sensing pathway with the help of fluorescent signals. Results indicated a change in behavior of those pathways, indicating that the gene deletions clearly affected sugar signaling. These results might contribute to the engineering development of improved xylose utilization by yeast. (Less)
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author
Fjölnisdóttir, Birta Líf LU
supervisor
organization
alternative title
Utvärdering av effekterna av nya gentekniska målmolekyler på sockersignalleringen i S. cerevisiae
course
KMBM01 20181
year
type
H2 - Master's Degree (Two Years)
subject
keywords
S. cerevisiae, yeast, sugar signaling, Snf3p/Rgt2p, SNF1p/Mig1p, cAMP/PKA, xylose, sustainability, flow cytometry, biosensor, applied microbiology, teknisk mikrobiologi
language
English
id
8950157
date added to LUP
2018-06-18 16:16:54
date last changed
2018-06-18 16:16:54
@misc{8950157,
  abstract     = {{Baker´s yeast S. cerevisiae has been engineered in order to enable xylose uptake and utilization from lignocellulosic biomass as this yeast cannot naturally metabolize this pentose sugar. However, xylose is not recognized as a fermentable sugar by S. cerevisiae and recent studies on the effect of xylose on the three main sugar signaling pathways (Snf3p/Rgt2p, SNF1/Mig1pt and cAMP/PKA) have indicated that S. cerevisiae cannot sense extracellular xylose. In parallel, it was recently shown that the combined deletions of HOG1, IRA2, GRE3 and ISU2 gave epistatic interactions resulting in improved growth and xylose uptake in recombinant S. cerevisiae strains containing the XI pathway. The objective of the present study was to explore the effects of those gene deletions on sensing and signaling for the three sugar signaling pathways. Deletions of IRA2, ISU1 and HOG1 were constructed in S. cerevisiae strains containing the XR-XDH pathway as well as a biosensor for each of the signaling pathways and the response was recorded using flow cytometry. Results confirmed clear effects of the deletions on all the signaling pathways, with ira2Δ mutants mimicking high glucose signal with constitutive activation of PKA and hog1Δ mutants giving low glucose responses. When combined with the deletion of ISU1, the SNF1/Mig1p pathway was clearly affected since subpopulations were alleviated.}},
  author       = {{Fjölnisdóttir, Birta Líf}},
  language     = {{eng}},
  note         = {{Student Paper}},
  title        = {{Understanding the Effects of Novel Engineering Targets on Sugar Sensing in S. cerevisiae}},
  year         = {{2018}},
}