A study of the effect of heat shock and metal ions on protein synthesis in Neurospora crassa cells

Variability in Protein Expression in Marine-Derived Purpureocillium lilacinum Subjected to Salt and Chromium Stresses

Abiotic factors can cause substantial limitation of growth of microbes. A combination of salinity stress along with chromium (Cr+6), one of the carcinogen, can pose an immediate threat to any living system. To understand how salinity (0, 35 and 100 PSU) and Cr(VI) stress (0, 100 and 500 ppm), affects cells at the molecular level, the cellular response of Purpureocillium lilacinum to the individual as well the combination of both the stresses were studied by peptide mass fingerprinting technique. The study reports 1412 proteins, of which 105 proteins were found to be present across all conditions. The most prevalent functional class expressed was genetic information processing. Proteins involved in free radical scavenging were up-regulated in response to the oxidative stress generated due to both the applied stresses while expression of metal chelators, transporters systems, indicated towards multiple stress tolerance mechanisms to combat synergistic effects of salt and Cr stress.

Heat-shock response of the entomopathogenic fungus Beauveria brongniartii

The heat-shock response of five strains of the entomopathogenic fungus Beauveria brongniartii was studied using two-dimensional (2D) gel electrophoresis. The fungal cells were heat shocked at 45 °C for 1 h and the total cellular protein was subjected to 2D gel electrophoresis. Proteins were separated in the first dimension using isoelectric focusing (pH range of 3.0–10) and in the second dimension by sodium dodecyl sulphate – polyacrylamide gel electrophoresis. More than 150 polypeptides for each strain were visualized by silver staining and have been assigned individual numbers as polypeptide coordinates. Analysis of the polypeptide map obtained by 2D gels indicated three patterns; several unique heat-shock proteins (HSPs) were (i) induced, (ii) enhanced, or (iii) repressed. Some of the HSPs induced by 45 °C were unique for each of the strains tested. Identification of heat-inducible protein synthesis or repression has ramifications for field survival and performance of entomopathogenic fungi. As well, the HSPs can be used as "signature proteins" for identification pruposes and this raises the possibility of using HSPs as a diagnostic tool applicable to other pest control fungi.Key words: heat-shock proteins, heat-shock response, two-dimensional electrophoresis, entomopathogenic fungi, Beauveria brongniartii.

Biochemical effects of heat shock and caffeine on post-irradiation oxic and anoxic damage in barley seeds of low and high water content

Wet heat shock (60 degrees C, 90 s) and caffeine (3.8 X 10(-4) M) afford significant radioprotection against post-irradiation O2-dependent damage which develops in seeds of approximately 3.5% moisture content. The damage was assessed in terms of seedling injury on the eighth day of growth. An increase in seedling injury is clearly seen, associated with a parallel increase in the peroxidase activity. There is a concomitant decrease in the content of total peroxides. Both these post-irradiation treatments potentiate the O2-independent component of seedling injury, irrespective of the seed moisture content. Analysis of the peroxidase activity in the seedlings using non-denaturing polyacrylamide gel electrophoresis reveals that two additional bands appear with the post-irradiation oxic damage. Radioprotection against this damage by caffeine, heat shock and O2-free post-irradiation hydration is accompanied by the disappearance of these two additional bands. However there is no appearance of the two additional bands in the peroxidase family even though the enzyme activity is substantially increased due to the action of caffeine and/or heat shock on the post-irradiation O2-independent pathway of damage. The probable mechanisms of radioprotection are discussed in this paper.

Microbial stress proteins

There is general agreement that a function, perhaps the major function, of stress proteins under normal physiological conditions is to help assembly and disassembly of protein complexes and to catalyse protein-translocation processes. It remains unclear, however, as to what role these processes play in stressed cells. It could be that cells under stress produce abnormal, misfolded or otherwise damaged proteins and that increased synthesis of stress proteins is required to counter protein modifications. A role for stress proteins in recovery of cells from stress, as opposed to a role in helping cells to withstand a lethal stress, is thus suggested. The intracellular location of stress proteins, in the unstressed and stressed cell, is worthy of further studies. Members of the hsp70 family are associated with the cytosol, mitochondria and endoplasmic reticulum. There is evidence, particularly from studies on mammalian cells (Tanguay, 1985; Welch and Mizzen, 1988; Arrigo et al., 1988), that following stress hsps migrate to various cellular compartments and subsequently delocalize after stress. However, there is little comparable data from microbial systems for this phenomenon (e.g. Rossi and Lindquist, 1989). The question as to the role of stress proteins in the transient acquisition of thermotolerance remains to be answered. It is insufficient to equate the kinetics of stress-protein synthesis with acquisition of thermotolerance. Quantitative data on the amount of stress protein present at various times, including the recovery period, is required. The demonstration that microbial stress proteins are important antigenic determinants of micro-organisms causing major debilitating diseases in the world is an exciting observation. Studies on the interplay of pathogen and host, both carrying similar antigenic hsp determinants, will be a challenging area for future research. It is likely that E. coli and Sacch. cerevisiae, with their well-established biochemical and genetic properties, will continue to be the experimental systems of choice for studies on stress proteins. On the other hand, it is encouraging that studies on other micro-organisms have expanded in the past few years and have made substantial contributions towards our understanding of the stress response. The ubiquitous nature of the stress response and the remarkable evolutionary conservation of the stress proteins continue to be attractive areas for research.

The heat shock response of Neurospora crassa: stress-induced thermotolerance in relation to peroxidase and superoxide dismutase levels

Heat shock and other treatments, including cadmium chloride, hydrogen peroxide and sodium arsenite, led to the induction of high levels of peroxidase activity as well as thermotolerance in Neurospora crassa. No correlation was apparent between superoxide dismutase levels and development of thermotolerance following exposure to these stress conditions. A prominent role for peroxidase in protection against damage by toxic products of oxygen is suggested.