Induction of Heat-Shock Proteins at Permissive Growth Temperatures in the Plasmodium of the Myxomycete Physarum polycephalum

Abstract

When synchronous plasmodia of the myxomycete Physarumpolycephalum were submitted to temperature shifts from 22 "C to 32 "C, the highest physiological temperature, protein synthesis was increased during at least 10 h. Moreover during 2 h, four proteins (69, 74, 82 and 105 kDa) showed a transient increase of their synthesis, independently of the period of the temperature shift during the cell cycle. The stability of these proteins and the susceptibility of their synthesis to actinomycin suggested that they corresponded to four different proteins. Temperature shifts from 22 "C or 29 "C to 37 "C, a non-physiological temperature, demonstrated that the 69-kDa, 74-kDa, 82-kDa and 105-kDa proteins were identical to the four heat-shock proteins which could be detected in Physarum. Although the physiological significance of these heat-shock proteins remained unclear, comparison between the extent of their synthesis and the length of the mitotic delays induced by various temperature shifts ruled out a direct relationship between mitotic delays and synthesis of the 74-kDa, 82-kDa and 105-kDa proteins.The synchronous mitosis of the plasmodial nuclei of the myxomycete Physarum polycephalum is controlled by at least two regulatory pathways [I -41. One of these pathways is involved in the triggering of both mitosis [5] and the cyclic increase of thymidine kinase synthesis [6, 71. It could be mediated by the accumulation of a triggering substance acting at different concentration levels [6,8]. This regulatory pathway is perturbed by temperature shifts from 22 "C to 31 "C or 32 "C [5]. The latter temperature is the highest allowing growth and a normal cell cycle of Physarum plasmodia [5]. A transient inactivation of the triggering substance can account for the mitotic delays induced by temperature shifts to the highest permissive temperature [5, 71. This effect could be explained in several ways : the preferential inactivation at 32 "C of the triggering substance which has been synthesized at 22 "C [5, 71; an arrest in protein synthesis leading to an inbalance between the synthesis and the inactivation of the triggering substance after a shift to 32 "C; an inactivation of the triggering substance caused by the transient synthesis of an inhibitor induced by temperature shifts [7]. In order to exclude or to favor one of these possibilities we investigated the synthesis of new proteins after temperature shifts. We observed that temperature shifts between some permissive temperatures (22 -32 "C) induce the transient synthesis of several proteins, which correspond to the heat-shock proteins of Physarum plasmodia [2]. MATERIALS A N D METHODS Plasmodial StrainsPlasmodial strain LU860 x LU910 was obtained from a cross between amoebal strain LU860 (mutA1, matBI, fusAZ, fusB1, fusCZ, l e u l -) [9] and amoebal strain LU910 (matA3, matB3, fusA1, fusB1, fusC1, erne',. Plasmodial strain C1 was derived directly from C1 amoebae [lo-121. Microplasmodia were grown in liquid culture in 500-ml vials containing 150 ml semi-defined medium and submit...

Heat-shock response of the entomopathogenic fungusBeauveria brongniartii

“…As an example, HSP 106.4 of strain 979 could be similar to HSP 104 of S. cerevisiae, which has been reported to be crucial for induction of thermotolerance (Sanchez and Lindquist 1990). Induction of HSPs with molecular masses of 101 and 105 kDa have also been reported in the filamentous fungi Fonsecaea pedrosi, Aspergillus niger, Neurospora crassa, and Physarum polycephalum (Laurent-Winter and Ibrahim-Granet 1992;Kapoor 1983;Stephanou and Demopoulos 1986;Wright and Tollon 1982). A comparison of the molecular masses of the other HSPs observed in this study with the masses of HSPs in other filamentous fungi also suggest a basis for the existence of probable homology.…”

“…A comparison of the molecular masses of the other HSPs observed in this study with the masses of HSPs in other filamentous fungi also suggest a basis for the existence of probable homology. The HSPs observed in this study may correspond to the HSPs already described in Fpedrosi (HSPs92.5,67.5,62.5,55.5,54,43.9,44.5,39.5,32,35,30.5,30.7, and 24.7) (Laurent-Winter and Ibrahim-Granet 1992), N. crassa (HSPs 99,78,43,35,and 23) (Kapoor 1983(Kapoor , 1986, Aspergillus niger (HSPs 98, 95, and 85) (Stephanou and Demopoulos 1986), P. polycephalum (HSPs 82, 74, and 69) (Wright and Tollon 1982), Ustilago maydis (HSP 70) (Holden et al 1989). Achlya ambisexualis (HSP 83) (Brunt and Silver 1991), and Tetrahymena thermophila (HSP 60) (McMullin and Hallberg 1988).…”

Small heat shock proteins in the development of thermotolerance in Pisolithus sp.

“…In thermal stress response, the synthesis of HSPs has been well documented in Saccharomices cerevisiae (Sanchez and Lindquist, 1990;Sanchez et al, 1992;Ueom et al, 2003), Neurospora crassa (Kapoor, 1986;Plesofsky-Vig and Brambl, 1987;Kapoor et al, 1995;Mohsenzadeh et al, 1998), Aspergillus niger (Stephanou and Demopoulos, 1986), Physarum polycephalum (Wright and Tollon, 1982) and Ustilago maydis (Holden et al, 1989). The sHSPs, ranging from 12 to 42 kDa, are synthesized ubiquitously in eukaryotic and prokaryotic cells in response to heat and other stresses.…”

Regulation of tubulin synthesis during the cell cycle in the synchronous plasmodia of Physarum polycephalum

“…Among them, a few agents have a limited action on macromolecular biosyntheses, such as total RNA and protein syntheses (Eon-Gerhardt et al, 1981a,b;Wright and Tollon, 1982. These agents have been used extensively in the case of thymidine kinase (EonGerhardt et al, 1981a,b;Wright and Tollon, 1979 and histones (Loidl and Grobner, 1987), in order to define at the phenomenological level the regulatory pathways playing a role in the onset and in the arrest of the synthesis of these proteins.…”

“…It has been well documented that in Physarurn synchronous plasmodia, external perturbations generally delay the onset of mitosis (Sachsenmaier and Rusch, 1964;Sachsenmaier and Becker, 1965;Cummins et al, 1965;Brewer and Rusch, 1968;Hildebrandt and Sauer, 1973;Grobner and Loidl, 1982). Among them, a few agents have a limited action on macromolecular biosyntheses, such as total RNA and protein syntheses (Eon-Gerhardt et al, 1981a,b;Wright and Tollon, 1982). These agents have been used extensively in the case of thymidine kinase (Eon-Gerhardt et al, 1981a,b;Wright and Tollon, 1979 and histones (Loidl and Grobner, 1987), in order to define at the phenomenological level the regulatory pathways playing a role in the onset and in the arrest of the synthesis of these proteins.…”