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First published online July 6, 2005
Journal of Experimental Biology 208, 2773-2781 (2005)
Published by The Company of Biologists 2005
doi: 10.1242/jeb.01705

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Ectothermy and endothermy: evolutionary perspectives of thermoprotection by HSPs

Ariel Shabtay and Zeev Arad^*

Department of Biology, Technion-Israel Institute of Technology, Haifa 32000, Israel

View larger version (47K): [in a new window]   Fig. 1. A typical embryonic (18 days, brain tissue) HSP response (representing Lohmann, Hy Line and Bedouin fowl strains) under heat shock conditions (6 h at 42°C) that precede the deleterious effects on hatchability (N=6 in each treatment). (A) HSF–DNA-binding activity detected by EMSA. EMSA was performed with a [32P]HSE oligonucleotide and whole brain tissue extracts. (B) Western blot analysis of HSP70 and HSP90. Each lane represents a different individual. C, control, unexposed individuals; HS, at the end of the heat exposure. A similar pattern was observed in 12-day-old embryos exposed to 43°C. (C) In vivo metabolic labelling analyzed by [35S]methionine incorporation. Ta, ambient temperature; time (h), heat shock period in hours.

View larger version (24K): [in a new window]   Fig. 2. The effect of embryonic heat exposure (8 h at 43°C) on hatchability in three layer strains (N=19) of fowl that differ in their heat resistance at maturity (Lohmann < Hy Line < Bedouin). Control, maintained at 37°C for the entire incubation period; 12d, heat shocked on day 12 of incubation; 18d, heat shocked on day 18 of incubation. Hatchability was markedly reduced in all strains on day 18. Different letters within each strain denote significant differences (ANOVA, P<0.05). Eggs of the Lohmann strain did not hatch at all if heat shocked on day 18.

View larger version (47K): [in a new window]   Fig. 3. A typical HSP response of postnatals (1 day, brain tissue) exposed to 6 h or 24 h at 42°C (N=6 in each treatment). (A) HSF–DNA-binding activity detected by EMSA. EMSA was performed with a [32P]HSE oligonucleotide and whole brain tissue extracts. Western blot analysis of HSF1 and HSF3 (B) or HSP70 and HSP90 (C). Each lane represents a different individual. C, control, unexposed individuals; HS, at the end of the heat exposure. A similar pattern was observed up to 25 days of age. (D) In vivo metabolic labelling analyzed by [35S]methionine incorporation. Ta, ambient temperature; Tb, body temperature.

View larger version (55K): [in a new window]   Fig. 4. Acquired thermotolerance of mature Leghorn individuals following a single embryonic heat exposure. Presented is the expression of HSP90 in the brain tissue. Actin levels were used to detect equal amounts of loaded proteins. Control, not exposed to heat as embryos; 6d, exposed to heat (6 h at 42°C) on day 6 of incubation; C, unexposed mature individuals (5 months of age); HS, heat exposure at maturity (8 h at 40°C during two consecutive days). Percentage survival (at the bottom of the figure) was not affected by the embryonic heat exposure (unpaired t-test, P=0.34) and is expressed as means ± S.D. (N=19).

View larger version (61K): [in a new window]   Fig. 5. In vivo real-time measurements of the heat shock response of mature fowl of three strains that differ in their resistance to heat. (A) Body temperature (Tb) regulation (N=3 in each strain). (B) HSF–DNA-binding activity detected by EMSA. EMSA was performed with a [32P]HSE oligonucleotide and whole blood cell extracts. (C) Levels of HSP70–mRNA in whole blood cells, detected by chicken HSP70 cDNA as a probe. (D) Protein levels of HSP70 detected by western blot analysis. Leghorn-C, heat sensitive fowl; Leghorn-16d, phenotypically heat-adapted fowl; Bedouin, genetically heat-resistant fowl. Red arrows indicate repeated elevations of ambient temperature, in the case of the Bedouin fowl up to 43.5°C. B–D represent three individuals of each strain.

View larger version (16K): [in a new window]   Fig. 6. De novo synthesis of a 270 kDa protein in liver tissue of 1-day-old postnatals in response to heat shock (2 h, 42°C). No such response was observed in 18-day-old embryos (score zero in densitometry of both control and heat-shocked individuals). This protein was identified by mass spectrometry analysis as fatty acid synthase (FAS). Each lane represents a different individual. C, control, unexposed individuals; HS, at the end of the heat exposure.