Rapid cold-hardening protects <Emphasis Type="Italic">Drosophila melanogaster</Emphasis> from cold-induced apoptosis |
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Authors: | Shu-Xia Yi Clifford W Moore Jr" target="_blank">Richard E LeeJr |
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Institution: | (1) Department of Zoology, Miami University, Oxford, OH 45056, USA |
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Abstract: | The rapid cold-hardening (RCH) response increases the cold tolerance of insects by protecting against non-freezing, cold-shock
injury. Apoptosis, or programmed cell death, plays important roles in development and the elimination of sub-lethally damaged
cells. Our objectives were to determine whether apoptosis plays a role in cold-shock injury and, if so, whether the RCH response
protects against cold-induced apoptosis in Drosophila melanogaster. The present study confirmed that RCH increased the cold tolerance of the adults at the organismal level. No flies in the
cold-shocked group survived direct exposure to ‒7°C for 2 h, whereas significantly more flies in the RCH group survived exposure
to ‒7°C for 2 h after a 2-h exposure to 5°C. We used a TUNEL assay to detect and quantify apoptotic cell death in five groups
of flies including control, cold-shocked, RCH, heat-shocked (37.5°C, 30 min), and frozen (‒20°C, 24 h) and found that apoptosis
was induced by cold shock, heat shock, and freezing. The RCH treatment significantly improved cell viability by 38% compared
to the cold-shocked group. Cold shock-induced DNA fragmentation shown by electrophoresis provided further evidence for apoptosis.
SDS-PAGE analysis revealed an RCH-specific protein band with molecular mass of ∼150 kDa. Western-blotting revealed three proteins
that play key roles in the apoptotic pathway: caspase-9-like (apoptotic initiator), caspase-3-like (apoptotic executioner)
and Bcl-2 (anti-apoptotic protein). Consequently, the results of this study support the hypothesis that the RCH response protects
against cold-shock-induced apoptosis. |
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Keywords: | Drosophila melanogaster Apoptosis TUNEL assay Rapid cold-hardening Cold shock |
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