Autophagy is a conserved pathway for the bulk degradation of cytoplasmic components in all eukaryotes. This process plays a critical role in the adaptation of plants to drastic changing environmental stresses such as starvation, oxidative stress, drought, salt, and pathogen invasion. This paper summarizes the current knowledge about the mechanism and roles of plant autophagy in various plant stress responses.
Adaptation, Physiological ; Arabidopsis ; genetics ; physiology ; Arabidopsis Proteins ; genetics ; metabolism ; Autophagy ; genetics ; Disease Resistance ; Plant Diseases ; immunology ; Saccharomyces cerevisiae ; genetics ; Sequence Homology ; Stress, Physiological

Improving stress tolerance of the microbial producers is of great importance for the process economy and efficiency of bioenergy production. Key genes influencing ethanol tolerance of brewing yeast can be revealed by studies on the molecular mechanisms which can lead to the further metabolic engineering manipulations for the improvement of ethanol tolerance and ethanol productivity. Trahalose shows protective effect on the cell viability of yeast against multiple environmental stress factors, however, further research is needed for the exploration of the underlying molecular mechanisms. In this study, the promoter region of the trehalose-6-phosphate synthase gene TPS1 was cloned from the self-flocculating yeast Saccharomyces cerevisiae flo, and a reporter plasmid based on the expression vector pYES2.0 on which the green fluorescence protein EGFP was directed by the TPS1 promoter was constructed and transformed to industrial yeast strain Saccharomyces cerevisiae ATCC4126. Analysis of the EGFP expression of the yeast transformants in presence of 7% and 10% ethanol revealed that the P(TPS1) activity was strongly induced by 7% ethanol, showing specific response to ethanol stress. The results of this study indicate that trehalose biosynthesis in self-flocculating yeast is a protective response against ethanol stress.
Base Sequence ; Cloning, Molecular ; Ethanol ; metabolism ; pharmacology ; Glucosyltransferases ; biosynthesis ; genetics ; Molecular Sequence Data ; Promoter Regions, Genetic ; genetics ; Saccharomyces cerevisiae ; enzymology ; genetics ; metabolism ; Stress, Physiological ; physiology

Biofuels are renewable and environmentally friendly, but high production cost makes them economically not competitive, and the development of robust strains is thus one of the prerequisites. In this article, strain improvement studies based on the information from systems biology studies are reviewed, with a focus on their applications on stress tolerance improvement. Furthermore, the contribution of systems biology, synthetic biology and metabolic engineering in strain development for biofuel production is discussed, with an expectation for developing more robust strains for biofuel production.
Biofuels ; Genetic Engineering ; methods ; Industrial Microbiology ; methods ; trends ; Lignin ; metabolism ; Saccharomyces cerevisiae ; genetics ; metabolism ; physiology ; Synthetic Biology ; methods ; Systems Biology ; methods

To investigate the function of STT3a gene in salt adaptation and flagellar regeneration of Dunaliella salina (D. salina), a pair of degenerate primers was designed according to conserved homologous amino acid sequences of VCVFTA and DVDYVL of STT3a from Chlamydomonas, Arabidopsis thaliana and other organisms. A cDNA sequence of 1 650 bp encoding a whole functional domain of STT3a was amplified from D. salina by RT-PCR and 3' Rapid Amplification of cDNA Ends (RACE), which shared homology with Chlamydomonas (48%), Arabidopsis thaliana (50%), Homo sapiens (46%), etc. Real-time fluorescence quantitative PCR (real-time Q-PCR) demonstrated that the STT3a mRNAs from D. salina were induced by increased concentration of NaCl, and increased to 11-fold higher by 3.5 mol/L NaCl than that by 1.5 mol/L NaCl (P < 0.01). Also, STT3a mRNA of D. salina maintained at a higher level in the process of flagellar regeneration with than without experiencing deflagellar treatment. In conclusion, the findings of this study demonstrate that the high expression of the STT3a gene enhances the capability of salt adaptation and flagellar regeneration in D. salina.
Adaptation, Physiological ; physiology ; Arabidopsis ; enzymology ; Chlamydomonas ; enzymology ; Chlorophyta ; enzymology ; genetics ; Cloning, Molecular ; Flagella ; metabolism ; Hexosyltransferases ; chemistry ; genetics ; metabolism ; Membrane Proteins ; chemistry ; genetics ; metabolism ; RNA, Messenger ; genetics ; metabolism ; Saccharomyces cerevisiae Proteins ; genetics ; metabolism ; Sodium Chloride ; pharmacology

Nicotinamide adenine nucleotide (NADH), the key cofactor in the metabolic network, plays an essential role in biochemical reaction and physiological function of industrial strains. Manipulation of NADH availability and form is an efficient and easy way to redirect the carbon flux to the target metabolites in industrial strains. We reviewed the physiological function of NADH. Detailed strategies to manipulate NADH availability are addressed. NADH manipulation to enhance metabolic function of industrial strains was discussed and potential solutions were suggested.
Bacteria ; metabolism ; Energy Metabolism ; genetics ; physiology ; Fermentation ; Industrial Microbiology ; Lactococcus lactis ; metabolism ; NAD ; metabolism ; physiology ; Saccharomyces cerevisiae ; metabolism ; Streptococcus mutans ; metabolism

To study the effect of the osmotic stress in the microenvironment on the growth and metabolism of the encapsulated cells under aerobic condition, Osmo-sensitive yeast Y02724 and high-osmotic resistant yeast Hansel were used as models to explore the growth and metabolism state of the cells cultivated inalginate-chitosan-alginate (ACA) microcapsules. The changes of the yeast cells' specific growth rate, maximum product quantity and the secretion of ethanol and glycerol were analyzed. For Y02724, the yield of ethanol was increased in the ACA microenvironment compared to suspension cultivation. For Hansel, the maximum growth speed of microencapsulated cultivation had no obvious difference compared to the suspension cultivation. Moreover, after encapsulation, the production of glycerol was decreased for both Y02724 and Hansel compared to suspension cultivation. In conclusion, osmotic stress existed in the ACA microcapsules and affected the growth and metabolism of the cells.
Alginates ; metabolism ; Capsules ; metabolism ; Cell Culture Techniques ; methods ; Chitosan ; metabolism ; Osmosis ; physiology ; Osmotic Pressure ; Polylysine ; analogs & derivatives ; metabolism ; Saccharomyces cerevisiae ; growth & development ; metabolism ; Yeasts ; classification ; growth & development ; metabolism

The physiological roles of the glutathione(GSH)/glutathione peroxidase(GPx) system in protecting microbial cells against oxidative stress were reviewed. In eukaryotic model microbe Saccharomyces cerevisiae,this system is obligatory in maintaining the redox balance and defending the oxidative stress. However, the GSH/GPx system only conditionally exists in prokaryotes. Namely,for those prokaryote bacteria containing glutathione reductase and GPx, e.g. Haemophilus influenzae and Lactococcus lactis, by taking up GSH, they might develop a conditional GSH-dependent GPx reduction system, which conferred cells a stronger resistance against oxidative challenge.
Glutathione ; metabolism ; physiology ; Glutathione Peroxidase ; metabolism ; physiology ; Glutathione Reductase ; physiology ; Haemophilus influenzae ; physiology ; Lactococcus lactis ; physiology ; Oxidative Stress ; physiology ; Saccharomyces cerevisiae ; enzymology ; physiology

ATP-NAD kinase phosphorylates NAD to produce NADP by using ATP, whereas ATP-NADH kinase phosphorylates both NAD and NADH. Three NAD kinase homologues, namely, Utr1p, Pos5p and Utr1p, exist in the yeast Saccharomyces cerevisiae, which were all confirmed as ATP-NADH kinases and found to be important to supply NADP(H) for yeast cells. In S. cerevisiae, fatty acid beta-oxidation is restricted to peroxisomes and peroxisomal NADPH is required for beta-oxidation of unsaturated fatty acids with the double bonds at even positions. Single and double gene disruption strains of NAD kinase genes, i.e., utr1, pos5, yef1, utr1yef1, utr1pos5 and yef1pos5 were constructed by PCR-targeting method. The utilization ability of these mutants for unsaturated fatty acids with the double bonds at even or uneven positions was examined, with wild type BY4742 as positive control cell, and fatty-acyl-CoA oxidase gene deletion mutant (fox1) and peroxisomal NADP-dependent isocitrate dehydrogenase isoenzymes gene deletion mutant (idp3) as negative control cells. The results indicated that the NAD kinase homologues, especially Pos5p, were critical for supplying NADP and then NADPH in peroxisomal matrix. NADP, which was supplied mainly by Utr1p, Pos5p and Yef1p, particularly by Pos5p, was proposed to be able to transfer from outside of peroxisome into peroxisomal matrix and then converted to NADPH by Idp3p.
Fatty Acids, Unsaturated ; metabolism ; Mitochondrial Proteins ; physiology ; NADP ; metabolism ; Oxidation-Reduction ; Phosphotransferases (Alcohol Group Acceptor) ; physiology ; Saccharomyces cerevisiae ; growth & development ; metabolism ; Saccharomyces cerevisiae Proteins ; physiology

It has long been thought that bioprocess, with their inherent measurement difficulties and complex dynamics, posed almost insurmountable problems to engineers. A novel software sensor is proposed to make more effective use of those measurements that are already available, which enable improvement in fermentation process control. The proposed method is based on mixtures of Gaussian processes (GP) with expectation maximization (EM) algorithm employed for parameter estimation of mixture of models. The mixture model can alleviate computational complexity of GP and also accord with changes of operating condition in fermentation processes, i.e., it would certainly be able to examine what types of process-knowledge would be most relevant for local models' specific operating points of the process and then combine them into a global one. Demonstrated by on-line estimate of yeast concentration in fermentation industry as an example, it is shown that soft sensor based state estimation is a powerful technique for both enhancing automatic control performance of biological systems and implementing on-line monitoring and optimization.
Algorithms ; Bioreactors ; microbiology ; Cell Culture Techniques ; methods ; Cell Proliferation ; Ethanol ; metabolism ; Fermentation ; physiology ; Hydrogen-Ion Concentration ; Models, Biological ; Models, Statistical ; Online Systems ; Oxygen ; metabolism ; Oxygen Consumption ; physiology ; Saccharomyces cerevisiae ; growth & development ; metabolism ; Software

A combination of three amino acids including 1.0 g/L isoleucine, 0.5 g/L methionine and 2.0 g/L phenylalanine was found to enhance ethanol tolerance of a self-flocculating fusant of Schizosaccharomyces pombe and Saccharomyces cerevisiae. When subjected to 20% (V/V) ethanol for 9 h at 30 degrees C, all cells died whereas 57% remained viable for the cells grown in the presence of the three amino acids. Based on the analysis of protein amino acid composition of plasma membranes and the determination of plasma membrane fluidity by measuring fluorescence anisotropy using diphenylhexatriene as a probe, it was found that the significantly increased ethanol tolerance of cells grown with the three amino acids was due to the incorporation of the supplementary amino acids into the plasma membranes, thus resulting in enhanced ability of the plasma membranes to efficiently counteract the fluidizing effect of ethanol when subjected to ethanol stress. This is the first time to report that plasma membrane fluidity can be influenced by protein amino acid composition of plasma membranes.
Amino Acids ; analysis ; physiology ; Cell Membrane ; chemistry ; Culture Media ; Drug Tolerance ; Ethanol ; pharmacology ; Flocculation ; Membrane Fluidity ; Saccharomyces cerevisiae ; chemistry ; drug effects ; growth & development ; Schizosaccharomyces ; chemistry ; drug effects ; growth & development