The heat shock response in congeneric land snails (Sphincterochila) from different habitats

Abstract

Land snails are subject to daily and seasonal variations in temperature and in water availability, and use heat shock proteins (HSPs) as part of their survival strategy. We used experimental heat stress to test whether adaptation to different habitats affects HSP expression in two closely related Sphincterochila snail species, a desert species, Sphincterochila zonata, and a Mediterranean-type species, Sphincterochila cariosa. Our findings show that in S. cariosa, heat stress caused rapid induction of Hsp70 proteins and Hsp90 in the foot and kidney tissues, whereas the desert-inhabiting species S. zonata displayed delayed induction of Hsp70 proteins in the foot and upregulation of Hsp90 alone in the kidney. Our study suggests that Sphincterochila species use HSPs as part of their survival strategy following heat stress and that adaptation to different habitats results in the development of distinct strategies of HSP expression in response to heat, namely the reduced induction of HSPs in the desert-dwelling species. We suggest that the desert species S. zonata relies on mechanisms and adaptations other than HSP induction, thus avoiding the fitness consequences of continuous HSP upregulation.

Fig. 1

Expression of Hsp70 isoforms (Hsp72 and Hsp74) and Hsp90 in the foot of S. cariosa and S. zonata following heat stress. Total protein was extracted from the foot of the control and heat-stressed snails immediately after heat stress (42 °C for 3 h) and after 1, 4, 24, and 48 h of recovery, and subjected to western blotting. Levels of Hsp70 isoforms (a) and Hsp90 (b) in tissue lysates are shown. All values are expressed as percentage of control snails (mean±SE). n = 7–12 snails for all data points, except for the 48-h recovery group in S. zonata (n = 4). Different letters above the bars denote significant differences within each species (lower case, S. cariosa; upper case, S. zonata). Asterisks denote significant differences between the two species (*p < 0.05; **p < 0.01; ***p < 0.001). C control, HS immediately after heat stress, Rec after recovery period

Fig. 2

Expression of Hsp72 and Hsp90 in the kidney of S. cariosa and S. zonata following heat stress. Total protein was extracted from the kidney of the control and heat-stressed snails immediately after heat stress (42 °C for 3 h) and after 1, 4, 24, and 48 h of recovery, and subjected to western blotting. Levels of Hsp72 (a) and Hsp90 (b) in tissue lysates are shown. All values are expressed as percentage of control snails (mean±SE). n = 7–12 snails for all data points, except for the 48-h recovery group in S. zonata (n = 4). Different letters above the bars denote significant differences within each species (lower case, S. cariosa; upper case, S. zonata). Asterisks denote significant differences between the two species (*p < 0.05; **p < 0.01). C control, HS immediately after heat stress, Rec after recovery period