title: Survival and hsp70 gene expression in Plutella xylostella and its larval parasitoid Diadegma insulare varied between slowly ramping and abrupt extreme temperature regimes.
abstract: BACKGROUND
  In nature, insects have evolved behavioural and physiological adaptations to cope with short term exposure to extreme temperatures. Extreme heat events may increase as a result of climate change; this in turn will affect insect population dynamics. We examined the effect of abrupt and ecologically relevant gradual exposure to high temperatures on the survival and hsp70 gene expression in diamondback moth (DBM) adults and the parasitoid Diadegma insulare, as well as in parasitized and non-parasitized DBM larvae.
  
  
  RESULTS
  Tolerance to high temperatures in DBM adults was higher than in D. insulare adults. There was no difference in the survival of DBM adults between abrupt and ramped increases from 25 to 38°C; however, at 40°C survival was higher when the temperature increased gradually. In contrast, more D. insulare adults survived when the temperature was ramped rather than shifted abruptly to both 38 and 40°C. There was no heat stress effect of up to 40°C on the survival of either parasitized or non-parasitized DBM larvae. In adults of both species, more hsp70 expression was observed when temperatures increased abruptly to 38°C compared to ramping. In contrast, at 40°C significantly more expression was found in insects exposed to the ramping rather than the abrupt regime. Hsp70 expression level was in agreement with adult survival data and appears to be a good indicator of stress levels. In parasitized and non-parasitized larvae, hsp70 expression was significantly higher after abrupt shifts compared to ramping at both temperatures.
  
  
  CONCLUSIONS
  Hsp70 gene expression was responsive to extreme temperatures in both DBM and D. insulare, which may underlie the ability of these insects to survive in extreme temperatures. Survival and hsp70 expression upon abrupt changes are distinctly different from those after ramping indicating that experimental protocol must be considered before extrapolating laboratory results to natural field situations.
authors.affiliation: Agriculture and Agri-Food Canada, Saskatoon Research Centre, Saskatoon, Saskatchewan, Canada.
authors.forename: Md Habibullah
authors.initials: MH
authors.lastname: Bahar
authors.forename: Dwayne
authors.initials: D
authors.lastname: Hegedus
authors.forename: Juliana
authors.initials: J
authors.lastname: Soroka
authors.forename: Cathy
authors.initials: C
authors.lastname: Coutu
authors.forename: Diana
authors.initials: D
authors.lastname: Bekkaoui
authors.forename: Lloyd
authors.initials: L
authors.lastname: Dosdall
mesh_terms: D000220:Adaptation, Biological; D000818:Animals; D005260:Female; D015870:Gene Expression; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics*; D006358:Hot Temperature; D007814:Larva; D008297:Male; D009036:Moths / Q000235:genetics*; D013696:Temperature
chemical_list: D018840:HSP70 Heat-Shock Proteins
references.citation: PeerJ. 2013 Feb 12;1:e11
references.pmid: 23638345
references.citation: Methods. 2010 Apr;50(4):S1-5
references.pmid: 20215014
references.citation: Proc Biol Sci. 2007 Dec 7;274(1628):2935-42
references.pmid: 17878142
references.citation: Cryobiology. 2008 Apr;56(2):159-62
references.pmid: 18295194
references.citation: Annu Rev Cell Dev Biol. 1995;11:441-69
references.pmid: 8689565
references.citation: Malar J. 2012 Jul 06;11:226
references.pmid: 22770378
references.citation: Environ Entomol. 2012 Dec;41(6):1653-61
references.pmid: 23321115
references.citation: Annu Rev Physiol. 1999;61:243-82
references.pmid: 10099689
references.citation: Comp Biochem Physiol A Mol Integr Physiol. 2010 Oct;157(2):177-83
references.pmid: 20601056
references.citation: PLoS One. 2012;7(3):e32758
references.pmid: 22427876
references.citation: Comp Biochem Physiol A Mol Integr Physiol. 2005 Jun;141(2):247-56
references.pmid: 15979913
references.citation: Pharmacol Ther. 1998 Nov;80(2):183-201
references.pmid: 9839771
references.citation: J Exp Biol. 2011 Nov 15;214(Pt 22):3713-25
references.pmid: 22031735
references.citation: Annu Rev Entomol. 2013;58:517-41
references.pmid: 23020617
references.citation: Mol Biol Rep. 2010 Jun;37(5):2265-72
references.pmid: 19685164