Genetic variation in thermal tolerance among natural populations of Drosophila buzzatii: down regulation of Hsp70 expression and variation in heat stress resistance traits

Abstract

Summary1. Thermal adaptation was investigated in the fruitfly Drosophila buzzatii Patterson and Wheeler. Two natural populations originating from a high-and a low-temperature environment, respectively, were compared with respect to Hsp70 (heat shock protein) expression, knock-down resistance and heat shock resistance. 2. Three main hypotheses were tested: (i) The expression level of Hsp70 in flies from the high-temperature habitat should be down-regulated relative to flies from the colder habitat. (ii) Flies having higher Hsp70 expression levels should be weakened most by a hardening treatment and go faster into coma, as Hsp70 level reflects stress intensity, and therefore display reduced heat knock-down resistance. (iii) Heat shock resistance should be increased in the population with highest Hsp70 expression because the level of Hsp70 is positively associated with this trait. 3. The results generally matched the hypotheses. Hsp70 expression was reduced in the high-temperature population. Knock-down resistance was higher in the hightemperature population and survival after heat shock was lower in the high-temperature population. 4. This study showed genetic differences in thermal tolerance between populations, indicating that high temperature in nature may be an important selective factor. Moreover, knock-down resistance in this study seems to be a more relevant trait than standard heat shock resistance for identifying thermal adaptation in natural populations.

Natural annual cycle of heat shock protein expression in land snails: desertversusMediterranean species ofSphincterochila

“…However, HSP expression might also incur fitness costs on individuals that regularly experience environmental stress, because of the reduced energy available for growth and reproduction, suggesting that evolution in harsh environments will result in selection for reduced HSP expression. This position is supported by our recent study in Sphincterochila snails and by studies in other organisms; for example, in natural populations of Drosophila from different climates (Sørensen et al, 2001) and in marine snail Tegula species of different biogeographical ranges (Tomanek and Somero, 2002).…”

“…Thus, because HSP expression might incur fitness costs on individuals that regularly experience environmental stress, evolution in harsh environments might result in selection for reduced HSP expression. Indeed, there are studies demonstrating lower levels of standing stocks of Hsp70 in the more thermally resistant species compared with the heat-sensitive ones Sørensen et al, 2001;Tomanek and Somero, 2002;Zatsepina et al, 2001). Our previous work (Mizrahi et al, 2010) supports this approach, demonstrating lower endogenous levels of Hsp72 in the desiccationresistant S. zonata compared with the desiccation-sensitive S. cariosa.…”

<I>Mamestra brassicae</I> Nucleopolyhedrovirus Infection and Enhancing Effect of Proteins Derived From <I>Xestia c-nigrum granulovirus</I> in Larvae of <I>Mamestra brassicae</I> and <I>Helicoverpa armigera</I> (Lepidoptera: Noctuidae) on Cabbage

“…Regarding the 6-fold induction, we consider that the experimental materials, which were taken from the northernmost province of China in Heilongjiang Province (Habin, 130°10'N, 46°40'E), may be an important factor. Some studies have shown that production of HSP70 in response to temperature shock is less intense in organisms that are more frequently exposed to unfavorable temperatures in their habitat than in organisms in benign conditions (Sørensen et al 2001;Lyytinen et al 2012). As the synthesis of HSP70s requires considerable energy and may thus occur at the cost of the synthesis of other proteins (Krebs & Loeschcke1994), northern populations might have evolved a less costly way to resist cold stress (Lansing et al 2000;Sørensen et al 2003).…”

Hsp70 and lipid peroxide levels following heat stress in Xeropicta derbentina (Krynicki 1836) (Gastropoda, Pulmonata) with regard to different colour morphs

“…These constitutively expressed stress proteins have chaperone function in protein folding processes, stabilize proteins in intracellular trafficking, and play an essential role in the assembly, degradation, and intracellular localization of proteins (Fink 1999;Hendrick and Hartl 1993;Mayer and Bukau 2005). It is known that different populations of a species can differ in their Hsp70 content and in their ability to induce Hsp70 as a response to heat, depending on their natural habitat and on the organisms' general ability of Hsp70 induction as, for example, shown in whole body homogenates of Drosophila sp flies (Bahrndorff et al 2006;Krebs and Feder 1997;Sørensen et al 2001). In case of X. derbentina, analyses of whole body homogenates have shown that the Hsp70 level of individuals depends on the population (Di , the life stage, the season, and the intensity of heat exposure (Dieterich et al 2012) as well as on the total load of heat stress over a given period of time Scheil et al 2011).…”