Figure legends
Figure 1. The molecular mechanisms of yeast underlying high
temperature response and thermotolerance
(1) Under normal circumstances, Hsf1p is inhibited by binding to Hsp70
which the association is weak. In response
to high temperature, Hsf1p is
released by binding of Hsp70p with misfolded protein, which then
phosphorylates and imported into the nucleus recruiting mediators (Head,
Middle, Tail, and Kinase) to increase the amount of RNA Pol II occupied
and reconstructing the chromatin distribution in the promoters. The
mediator is a conserved transcriptional coactivation complex. Its
component subunits of Med2p, Med3p, and Med15p can recruit on regulatory
regions of prompter, which enables smooth expression of target genes
involving heat shock protein (HSPs), protein homeostasis and trehalose
synthesis. (2) The number of new ribosomal proteins (RPs) and rRNAs do
not match, resulting in the orphan r-proteins aggregate. Hsf1p is
activated by them, which then stimulate the expression of protein
homeostasis genes. On the other hand, Ifh1p also activated by orphan
r-proteins, which in turn inhibits the synthesis of ribosomal protein
genes. (3) Ras-PKA pathway influence the activation of Msn2/3p by
phosphorylate. Stress leads Msn2/3p dephosphorylated, and then enters
the nucleus and activate the downstream regulated genes expression which
have stress response elements (STREs)
Figure 2. Deleterious effects of ethanol and acetic acid on
yeast cells and cellular adaptive response to stress
(1) Fps1p is the aquaglyceroporin channel which transports the acetic
acid from extracellular to cytoplasm, and it can interact with
regulatory proteins Rgc1p/Rgc2p. To cope with acetic acid stress, Fps1p
is closed in response to increases in cellular acetic acid
concentration. And other ATPase-dependent transporters (Pdr10, Pdr12,
Pma1) seem to play an important role in maintaining intracellular
concentration of
CH3COOH-/H+homeostasis. (2) Hyperphosphorylated Mks1p binds to Bmh1/2p, inhibiting
the Rtg3p and Rtg1p complexes translocate to nucleus and inhibits the
retrograde signals transmission in normal conditions. When the strains
exposure to acetic acid, Mitochondrial dysfunction leads to a decrease
in ATP content. And, Mks1p and Rtg2p are combined to inhibit the
Mks1-Bmh1/2p complex function of inhibiting the RTG pathway, resulting
in the activated Rtg3p-Rtg1p complex entering the cell nucleus to
regulate RTG-dependent nuclear genes expression such as IDH1, IDH12,
DLD3, PYC1. (3) HAA1 is sensitive to intracellular acetic acid.
After too much acetic acid dissociated in the cell to form acetate, it
will be activated by dephosphorylation, thus avoiding anionic toxicity.
(4) To deal with cell membrane destruction caused by ethanol, Ssk1p
which is Cytoplasmic phosphorelay intermediate regulator is activated by
overexpressing Ole1p, then sequentially activates Ssk2/22p and Pbs2p.
Finally, HOG pathway is stimulated by Pbs2p in response to ethanol
stress.
Figure 3. Functional
reaction to oxidant and Toxic molecule stress signals
(1) The activation of Yap1p is dependent or not on ROS caused by
oxidizing chemicals, it transits from cytoplasm to nucleus to stimulate
the expression of oxidative stress responsive gene such as GSH, GSN,
SOD2 and GLR1. And, Hyr1p or Ybp1p-Gpx3p complex can inhibit YAP1 output
from nuclear. (2) The unfolded protein response (UPR) signaling pathway
mainly contains two regulators, i.e., the Ire1p and Hac1p. The original
Hac1p mRNA contains introns which will inhibit its transcription
activity. Once Ire1p releases from upon ER stress, Hac1p introns is cut
to stimulate the expression of UPR genes expression. (3) The glutathione
(GSH) and thioredoxin (TRX) system be respectively regard as
representative of the non-enzymatic antioxidant system and enzyme
antioxidant system. The sulfydryl of GSH has reducing activity interact
with oxidizing chemicals to form oxidized glutathione (GSSG). Using
glutathione reductase and NADPH to restore GSSG to GSH. And, the
thioredoxin system includes thioredoxin reductase, thioredoxin and
thioredoxin peroxidase. Thioredoxin (TPX) is a class of thiol-rich
proteins. It can be used as a reducing substrate to maintain
intracellular redox together with thioredoxin reductase. (3) The
glutathione (GSH) and thioredoxin (TRX) system be respectively regard as
representative of the non-enzymatic antioxidant system and enzyme
antioxidant system. The sulfydryl of GSH has reducing activity interact
with oxidizing chemicals to form oxidized glutathione (GSSG). Using
glutathione reductase and NADPH to restore GSSG to GSH. And, the
thioredoxin system includes thioredoxin reductase, thioredoxin and
thioredoxin peroxidase. Thioredoxin (TPX) is a class of thiol-rich
proteins. It can be used as a reducing substrate to maintain
intracellular redox together with thioredoxin reductase.
Figure 4. Transcription Factor Engineering used to improve
strains industrial value and create new tools
(A) The conventional gene modifying methods including overexpression and
knockout can be brought into reconstructing metabolic networks,
especially in stress defense system. (B) gTME and heterologous
expression based on multi-TF structures provides a possibility for
promoting self-activity and enhancing gene transcription level that
contribute to the tolerance and productivity. (C) ATF together with
their
cognate
binding sites (CBS) and synthetic promoter (PSyn)
construct an orthorhombic gene expression system to regulate the genes
expression. (D) TF-based biosensors consist of effector domain (ED) for
sensing small molecules and DNA-binding domain (DBD) combined with DNA,
which provides more opportunities to
quantitatively evaluating substance
content.