Differential expression of heat‐shock proteins and spontaneous synthesis of HSP70 during the life cycle of Blastocladiella emersonii

Abstract

The heat-shock response in Blustocludiellu emrrsonii is dependent on the developmental stage. Cells exposed to elevated temperatures at different stages of the life cycle (sporulation, germination or growth) show a differential synthesis of heat-shock proteins (hsps). Of a total of 22 polypeptides induced, particular subsets of hsps appear in each phase, demonstrating a non-coordinate heat-shock gene expression. In contrast, heat-shock-related proteins (hsp76, hsp70, hsp39a) are spontaneously expressed at a high level during sporulation. By the criteria of two-dimensional gel electrophoresis and partial proteolysis mapping, the 70000-Da protein, whose synthesis is induced spontaneously during sporulation, is indistinguishable from the heat-inducible hsp70. The techniques of in vitro translation, and Northern analysis using a Drosophilu hsp70 probe, demonstrated that enhanced synthesis of hsp70, which occurs during heat-shock treatment and spontaneously during sporulation, is associated with an accumulation of hsp70 mRNA. These observations suggest that hsp70 gene expression is induced during sporulation.The heat-shock response is a typical physiological reaction qf prokaryotic and eukaryotic cells, induced by heat shock and other environmental stresses [I, 21. Certain genes, which are essentially quiescent at normal temperatures, are transiently transcribed and a new set of proteins (heat-shock proteins, hsps) is synthesized; frequently there is an accompanying interruption of normal protein synthesis. Although the pattern of hsps depends on the organism, the cell type, the temperature and the duration of exposure, both the induction mechanism at the transcriptional level and the structure of some of the proteins show a striking degree of conservation. Thus the Drosophilu hsp70 gene hybridizes to genomic sequences from many different organisms [3, 41 and can be induced concomitantly with the heat-shock response in different eukaryotes; heat-shock proteins from a series of eukaryotic organisms are antigenically related [5] and a consensus sequence element was identified in the promotor region of different hsp genes [6, 71. In addition to a transcriptional control, selective translation of the heat-shock mRNAs has been demonstrated in some systems [8 -101.The function of the hsps remains unknown, although the heat-shock response is frequently viewed as a cellular survival function conferring protection against the momentary and subsequent stress to the cell. Besides a role in the response to stress, these proteins may play a role in normal development. This hypothesis is based on the observation that some of the hsps are expressed during oogenesis and pupation in Drosophilu or during the two-cell stage in mouse embryo [II, 121. To understand better the possible role of hsps in differentiation it is important to investigate other developmental systems. An ideal model system is that of the aquatic fungus Blustocludiellu emersonii. This organism undergoes two distinct phases of cell differentiation: germination and ...

Transcriptome Analysis in Response to Heat Shock and Cadmium in the Aquatic Fungus Blastocladiella emersonii

“…Among the upregulated genes, only 34 of them were induced in both stages of development. These results suggest a developmental control of the heat shock response in B. emersonii, in agreement with previous data obtained through two-dimensional gel electrophoresis analysis of 35 S-labeled protein extracts that showed that different sets of heat shock proteins were synthesized in cells exposed to high temperature according to the stage of the fungus life cycle (8). Table 3 shows the genes with matches in the GenBank and/or Swiss Prot databases and classified as upregulated (threefold or more) in response to heat shock during sporulation (S) and germination (G) stages.…”

“…The heat shock response has been previously analyzed in B. emersonii and shown to be developmentally regulated, with different subsets of heat shock proteins (Hsps) being synthesized in response to heat stress during sporulation, germination, and vegetative growth (8). In addition, differences have been observed in the degree of induction of B. emersonii heat shock genes, depending on the stage of the fungus life cycle (24,47,57).…”

Differential stress gene expression during the development of Neurospora crassa and other fungi

“…hsp mRNA was also not detected in the zoospores of Blastocladiella emersonii, despite the fact that some other mRNA species were apparently stored in the spores [24,25]. The same result was obtained in Leptosphaeria maculans [26].…”

“…In B. emersonii, synthesis of various HSPs was induced by heat shock during the germination of spores: the induction of HSP24 appeared to be speci¢c for this stage and occurred only 45 min after germination begins [24]. The highest constitutive amounts of hsc70 and hsc80 transcripts in L. maculans were found in germinating spores, a state which might be associated with stress, because Leptosphaeria's invasion of the host plant takes place during germination [26].…”

Stress response in tardigrades: differential gene expression of molecular chaperones

“…Studies on sHsp regulation in dormancies of different organisms revealed heterogenous patterns (Bonato et al 1987;Yocum et al 1991;Denlinger et al 1992;Liang et al 1997a;Yocum et al 1998;Tammariello et al 1999;Cherkasova et al 2000;Goto and Kimura 2004;Rinehart et al 2007;Gkouvitsas et al 2008), indicating a diverse array of functions. An essential upregulation of shsp has been suggested for cold hardiness in the flesh fly Sarcophaga crassipalpis (Rinehart et al 2007).…”