Characterization of the heat-shock response in spinach (Spinacia oleracea L.)

Abstract

Spinach (Spinacia oleracea L. cultivar Longstanding Bloomsdale) grown at 20 °C was subjected to a range of rapid thermal shifts as high as 42 °C. There was a decrease in the level of protein synthesis following heat-shock treatments above 34 °C as indicated by the level of incorporation of L-[35S]methionine. In vivo labelled polypeptides and in vitro translation products of RNA isolated from leaf tissue and analyzed using one-dimensional sodium dodecyl sulfate polyacrylamide gel electrophoresis and fluorography, indicated that the temperature of induction of all 15 heat-shock proteins in the 20 °C grown plants was 36 °C. In addition, heat-shock RNA was coordinately expressed and the translation of heat-shock proteins was noncoordinate with respect to temperature. Treatment with cycloheximide and with chloramphenicol demonstrated that heat-shock protein synthesis in spinach was restricted to cytosolic ribosomes. Synthesis of some low molecular weight heat-shock proteins were insensitive to actinomycin D, suggesting greater stability of these heat-shock RNAs. The heat-shock polypeptide profile of plants grown at 10 °C was similar to that of plants grown at 20 °C, with 14 heat-shock proteins being induced at 36 °C. The growth temperature did not influence the final array of heat-shock proteins synthesized nor alter the temperature of induction of the heat-shock response.Key words: heat-shock response, heat-shock proteins, Spinacia oleracea.

Acclimation of the temperature set-points of the heat-shock response

“…While this is generally acknowledged , it is unclear why other organisms do not exhibit such plasticity (Koban et al, 1987;Somers et al, 1989;Mason-Apps et al, 1990). We could not identify any common pattern in species lacking plasticity of the HSR.…”

“…Organisms acclimated to warmer temperatures generally exhibit higher temperatures of HSR induction (T on ), and such acclimatory changes probably help fine-tune the HSR to variable thermal habitats (Hochachka and Somero, 2002). However, other studies have documented little or no change in the HSR temperature set-points with changes in growth temperature (Koban et al, 1987;Somers et al, 1989;Mason-Apps et al, 1990), and whether plasticity of the HSR is common to all organisms, and differs in organisms adapted to different thermal niches, is unclear (Tomanek and Somero, 1999). Also unknown are if and how changes in growth temperature affect the magnitude of expression of Hsps.…”

Heat sensitivity of Rubisco, Rubisco activase and Rubisco binding protein in higher plants

“…As shown by many stud ies listed, the deg ra da tion of the holoenzyme of Rubisco is par alleled by a de creas ing RA ac tiv ity, the for ma tion of RA ag gre gates and changes in the RA isoform pattern. The cru cial stress T for Triticum aestivum L. is at 35 °C -37.5 °C Crafts-Brandner 1999, Feller et al 1998), for Oryza sativa L. at 45 -50 °C (Bose et al 1999), for Secale cereale L. at 42 °C (Schmitz et al 1996), for Spinacia oleracea L. at 36 °C (Somers et al 1989, Rokka et al 2001, for Gossypium hirsutum L. at 35 -45 °C (Law and Crafts-Brandner 1999, Crafts-Brandner and Law 2000. Plants de velop tol er ance to nor mally le thal tem per a tures if they are pre-treated with high but non-lethal tem per a tures.…”

Association of 70-Kilodalton Heat-Shock Cognate Proteins with Acclimation to Cold

“…Experiments were conducted to determine whether the CAP79 complex was responsive to heat shock. When spinach leaf tissue was heat shocked for 3 h over a temperature range known to elicit the heat-shock response (33), only moderate changes were observed in the concentration of the CAP79 band, as judged by immunoblotting (Fig. 3B) (Fig.…”