Mutations in cognate genes of Saccharomyces cerevisiae hsp70 result in reduced growth rates at low temperatures.

Expression of two Saccharomyces cerevisiae genes (YG101 and YG103) that are related to the gene encoding inducible 70K protein (hsp70) is repressed upon heat shock. Mutations of the two genes were constructed in vitro and substituted into the yeast genome in place of the wild-type alleles. No phenotypic effect of single mutations of either gene was detected. However, cells containing both YG101 and YG103 mutations showed altered growth properties; double-mutation cells possess an optimal growth temperature of 37 degrees C rather than 30 degrees C and grow increasingly poorly as the temperature is lowered. Mutations of two other members of this hsp70-related multigene family, YG100 and YG102, have been analyzed (E. A. Craig and K. Jacobsen, Cell 38:841-849, 1984). Cells containing both YG100 and YG102 mutations cannot form colonies at 37 degrees C. Fusions between the YG101 and YG102 promoter regions and the YG100 and YG101 structural genes, respectively, were constructed. The YG101 promoter-YG100 structural gene fusion was not able to restore normal growth properties to the yg101- yg103- mutant. Also, yg100- yg102- cells containing the YG102 promoter-YG101 structural gene fusion were unable to grow at 37 degrees C. Failure of the protein products of related genes to rescue the relative cold sensitivity of growth suggests that members of the hsp70 multigene family are functionally distinct.     

Uncoating ATPase is a member of the 70 kilodalton family of stress proteins

The synthetic peptide, VGIDLGTTYSC, derived from the heat shock-induced genes human hsp70, Drosophila hsp70, S. cerevisiae YG100, and E. coli dnaK, elicited antibodies that recognized two constitutive proteins in bovine extracts. One of these proteins, 71 kd, has previously been identified as uncoating ATPase, an enzyme that releases clathrin from coated vesicles. This immunological data complemented the result that uncoating ATPase was indistinguishable from the constitutive mammalian 71 kd stress protein by either partial proteolytic mapping or two-dimensional gel analysis. In addition, affinity-purified uncoating ATPase antibodies recognize proteins in yeast identified as the gene products of the heat shock or heat shock cognate genes YG100 and YG102. The results show that uncoating ATPase is a member of the 70 kd heat shock protein family.     

Complex interactions among members of an essential subfamily of hsp70 genes in Saccharomyces cerevisiae.

Saccharomyces cerevisiae contains a large family of genes related to hsp70, the major heat shock-inducible gene of Drosophila melanogaster. One subfamily, identified by sequence homology, contains four genes, SSA1, SSA2, SSA3, and SSA4 (formerly YG100, YG102, YG106, and YG107, respectively). Previous studies showed that strains containing mutations in SSA1 and SSA2 are temperature sensitive for growth. SSA4, which is normally heat inducible and not expressed during vegetative growth, is expressed at high levels in ssa1 ssa2 strains at 23 degrees C. We constructed mutations in SSA3 and SSA4 and analyzed strains carrying mutations in the four genes. Strains carrying mutations in SSA3 SSA4 or SSA3 and SSA4 were indistinguishable from the wild type. However, ssa1 ssa2 ssa4 strains were inviable. SSA3, like SSA4, is a heat-inducible gene that is not normally expressed at 23 degrees C. Nevertheless, an intact copy of SSA3 regulated by the constitutive SSA2 promoter was capable of rescuing a ssa1 ssa2 ssa4 strain. This indicates that SSA3 encodes a functional protein and that the SSA1, SSA2, SSA3, and SSA4 gene products are functionally similar.     

Increased efficiency of targeted mutagenesis by CRISPR/Cas9 in plants using heat stress

The CRISPR/Cas9 system has greatly improved our ability to engineer targeted mutations in eukaryotic genomes. While CRISPR/Cas9 appears to work universally, the efficiency of targeted mutagenesis and the adverse generation of off‐target mutations vary greatly between different organisms. In this study, we report that Arabidopsis plants subjected to heat stress at 37°C show much higher frequencies of CRISPR‐induced mutations compared to plants grown continuously at the standard temperature (22°C). Using quantitative assays relying on green fluorescent protein (GFP) reporter genes, we found that targeted mutagenesis by CRISPR/Cas9 in Arabidopsis is increased by approximately 5‐fold in somatic tissues and up to 100‐fold in the germline upon heat treatment. This effect of temperature on the mutation rate is not limited to Arabidopsis, as we observed a similar increase in targeted mutations by CRISPR/Cas9 in Citrus plants exposed to heat stress at 37°C. In vitro assays demonstrate that Cas9 from Streptococcus pyogenes (SpCas9) is more active in creating double‐stranded DNA breaks at 37°C than at 22°C, thus indicating a potential contributing mechanism for the in vivo effect of temperature on CRISPR/Cas9. This study reveals the importance of temperature in modulating SpCas9 activity in eukaryotes, and provides a simple method to increase on‐target mutagenesis in plants using CRISPR/Cas9.     

Effect of temperature up-shift on fermentation and metabolic characteristics in view of gene expressions in <Emphasis Type="Italic">Escherichia coli</Emphasis>

Background  

Escherichia coli induces heat shock genes to the temperature up-shift, and changes the metabolism by complicated mechanism. The heat shock response is of practical importance for the variety of applications such as temperature-induced heterologous protein production, simultaneous saccharification and fermentation (SSF) etc. However, the effect of heat shock on the metabolic regulation is not well investigated. It is strongly desired to understand the metabolic changes and its mechanism upon heat shock in practice for the efficient metabolite production by temperature up-shift. In the present research, therefore, we investigated the effect of temperature up-shift from 37°C to 42°C on the metabolism in view of gene expressions.     

Lack of an HSP70 heat shock response in two Antarctic marine invertebrates

Members of the HSP70 gene family comprising the inducible (HSP70) genes and GRP78 (glucose-regulated protein 78 kDa) were identified in an Antarctic sea star (Odontaster validus) and an Antarctic gammarid (Paraceradocus gibber). These genes were surveyed for expression levels via Q-PCR after an acute 2-hour heat shock experiment in both animals and a time course assay in O. validus. No significant up-regulation was detected for any of the genes in either of the animals during the acute heat shock. The time course experiment in O. validus produced slightly different results with an initial down regulation in these genes at 2°C, but no significant up-regulation of the genes either at 2 or 6°C. Therefore, the classical heat shock response is absent in both species. The data is discussed in the context of the organisms’ thermal tolerance and the applicability of HSP70 to monitor thermal stress in Antarctic marine organisms.     

Small heat shock protein responses in leaf tissues of wheat cultivars with different heat susceptibility

The effect of heat stress on soluble proteins extracted from leaf tissues of bread (Triticum aestivum cv. Gönen-98, tolerant; cv. Cumhuriyet-75, susceptible; genome ABD) and durum (Triticum durum cv. Ege-88, tolerant; cv. Ankara-98, susceptible; genome AB) wheat cultivars differing in sensitivity to high temperature was examined by two-dimensional gel electrophoresis. At acclimation (37°C) and acclimation→high temperature (37°C→50°C) treatments compared to control (25°C), evaluation of gels revealed 31 proteins to be differentially expressed in first leaves as a result of heat stress in heat-susceptible and heat-tolerant cultivars of bread and durum wheats. All of the increased or decreased proteins in amount, newly synthesized and/or disappeared were in low-molecular-weight (LMW, 16.1–24.0 kDa) and generally acidic character (pI 4.8–6.9). The responses of the four cultivars were compared: Twenty-two of 31 proteins were detected as newly synthesized LMW heat shock proteins (LMW HSPs = small HSPs). The number of these sHSPs was different in cultivars which have the same genome. In addition, the number of the sHSPs in heat-tolerant cultivars was higher than in heat-susceptible cultivars. Some of the sHSPs were specific to cultivar. Most of the sHSPs synthesized at 37°C were also detected at 37°C→50°C treatment. It is suggested that sHSPs have special importance in two points: Firstly, sHSPs in cultivars showed abundance and diversity. Secondly, these proteins may play an important role in the acquiring of thermal tolerance.     

Transcriptional regulation of an hsp70 heat shock gene in the yeast Saccharomyces cerevisiae.

The yeast Saccharomyces cerevisiae contains three heat-inducible hsp70 genes. We have characterized the promoter region of the hsp70 heat shock gene YG100, that also displays a basal level of expression. Deletion of the distal region of the promoter resulted in an 80% drop in the basal level of expression without affecting expression after heat shock. Progressive-deletion analysis suggested that sequences necessary for heat-inducible expression are more proximal, within 233 base pairs of the initiation region. The promoter region of YG100 contains multiple elements related to the Drosophila melanogaster heat shock element (HSE; CnnGAAnnT TCnnG). Deletion of a proximal promoter region containing one element, HSE2, eliminated most of the heat-inducible expression of YG100. The upstream activation site (UAS) of the yeast cytochrome c gene (CYC1) can be substituted by a single copy of HSE2 plus its adjoining nucleotides (UASHS). This hybrid promoter displayed a substantial level of expression before heat shock, and the level of expression was elevated eightfold by heat shock. YG100 sequences that flank UASHS inhibited basal expression of UASHS in the hybrid promoter but not its heat-inducible expression. This inhibition of basal UASHS activity suggests that negative regulation is involved in modulating expression of this yeast heat shock gene.     

The Arabidopsis HSP18.2 promoter/GUS gene fusion in transgenic Arabidopsis plants: a powerful tool for the isolation of regulatory mutants of the heat-shock response

A detailed study of the expression of the promoter of the HSP18.2 gene from Arabidopsis fused to the bacterial gene for β-glucuronidase (GUS) in transgenic Arabidopsis plants is described. High levels of GUS activity were induced in all organs of transformants except for seeds during heat shock. The optimum temperature for expression of GUS in Arabidopsis was 35°C regardless of the plant growth temperature. Heat shock of 40°C did not induce any detectable levels of GUS activity. Pre-incubation at 35°C was found to have a protective effect on the induction of GUS activity at 40°C. GUS activity was also increased in response to a gradual increase in temperature. Histochemical analysis revealed that basal levels of GUS activity were induced in the vascular tissue of leaves and sepals, as well as at the tips of carpels, at the normal growth temperature. Heat treatment of a limited part of the plant tissue did not appear to cause systemic induction of GUS activity. To extend the analysis of the plant heat-shock response, we attempted to screen mutations in genes involved in the regulation of the induction of heat-shock protein (HSP) genes, using the GUS gene as a selection marker in transgenic Arabidopsis plants, and the results of this analysis are described.     

Expression of heat shock proteins in response to high and low temperature extremes in diapausing pharate larvae of the gypsy moth,Lymantria dispar

Diapausing pharate first instars of the gypsy moth, Lymantria dispar, respond to high temperature (37–41°C) by suppressing normal protein synthesis and synthesizing a set of seven heat shock proteins with M_rs of 90,000, 75,000, 73,000, 60,000, 42,000, 29,000, and 22,000 as determined by SDS-PAGE. During recovery at 25°C from heat shock, synthesis of the heat shock proteins gradually decreases over a period of 6 h, while normal protein synthesis is restored. A subset of these same heat shock proteins is also expressed during recovery at 4°C or 25°C from brief exposures to low temperature (-10 to 20°C), and its expression is more intense with increased severity of cold exposure. During recovery at 4°C after 24 h at ?20°C, both 90,000 and 75,000 M_r heat shock proteins are expressed for more than 96 h. While normal protein synthesis is suppressed during heat shock and recovery from heat shock, normal protein synthesis coincides with synthesis of the heat shock proteins during recovery from low temperatures, thus implying that expression of the heat shock proteins is not invariably linked to suppression of normal protein synthesis. Western transfer, using a monoclonal antibody that recognizes the inducible form of the human 70,000 M_r heat shock protein, demonstrates that immunologically related proteins in the gypsy moth are expressed at 4°C and during recovery from cold and heat shock.