Physiological effects of heat stress on Hawaiian picture-wing Drosophila: genome-wide expression patterns and stress-related traits

Climate change is compounding the threats to the future of biodiversity, already impacted by habitat loss, invasive species and diseases. In the Hawaiian Islands, many of the endemic species have narrow habitat ranges that make them especially vulnerable to climate change. The Hawaiian Drosophila, a remarkably diverse group of species with 11 listed as federally endangered, are thought to be sensitive to temperature changes. To examine the species differences in sensitivity of Hawaiian picture-wing Drosophila to temperature changes, wild populations of Drosophila sproati, a relatively common species, and Drosophila silvestris, a rare species, were collected from two locations on Hawaii Island and bred in common laboratory conditions. Adult flies were exposed to hot and cold temperatures and compared with adult flies at control temperatures. Drosophila silvestris adults were less tolerant to heat stress than D. sproati for both survival and sperm mobility. In contrast, D. silvestris adults were more tolerant to cold stress than D. sproati for adult survival. The expression of 4950 Gene Ontology annotated gene transcripts was also analysed in high-temperature-treated and control males to identify candidate genes related to heat tolerance. There were more than twice as many transcripts differentially expressed after high temperature treatment for D. silvestris (246 transcripts) as for D. sproati (106 transcripts), with 13 Gene Ontology terms enriched between temperatures for D. silvestris and merely three in D. sproati. The combined results are consistent with D. sproati occurring more widely today as well as occurring at lower elevations than D. silvestris and with a genetically based temperature response, which is more severe in D. silvestris at high temperatures than that in D. sproati. These experiments demonstrate the potential for different capacities of species to adapt to future climate change conditions as well as providing an explanation for historical changes in the distribution of species.

Ischaemia and the myocyte cytoskeleton: review and speculation

The cardiomyocyte cytoskeleton is composed of a highly organised complex array of specific proteins, arranged to transmit mechanical forces within the cell, to adjacent cells and the extracellular matrix, as well as to maintain internal organisation of cellular organelles. Although most of the published reports on cytoskeletal proteins refer to non-myocyte and smooth muscle cells, there seem significant homologies with cardiac structures. The specific interactions of some proteins in certain cytoskeletal structures are established and may be analogous to interactions in cardiac myocytes, but the roles of many proteins are uncertain, and the list of proteins that compose the cytoskeleton is likely to be incomplete. Some proteins may serve a dual role, contributing to signal transduction as well as to organisation and mechanical stability of the cell. Phosphorylation of cytoskeletal proteins, and elaborate cellular systems to control protein phosphorylation levels, suggest phosphorylation as a potential mechanism of controlling cytoskeletal assembly and remodelling. Disturbances of the cytoskeleton during ischaemia may produce alterations in cell structural integrity that could account for cell injury and death. Although mechanisms both of cytoskeletal assembly in normal cells and of cytoskeletal injury in ischaemic cells are currently poorly understood, research into the interactions of cytoskeletal proteins during ischaemia includes new approaches that may increase our understanding of the pathophysiology of the cardiac myocyte.