Antifreeze Proteins in Antarctic Fishes: Ecological and Organismal Physiology, Protein Structure-Function and Mechanism, Genetics and Evolution

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The Southern Ocean represents the world's coldest marine environment and its near-shore waters are perennially at the freezing point of seawater and replete with ice crystals. The group of marine teleost fishes are hypo-osmotic to seawater and therefore would readily freeze in these waters from nucleation by environmental ice. Cold-adapted fishes have more serum electrolytes, but these are insufficient to prevent freezing in Antarctic fishes. A number of polar and subpolar fish evolved special biological antifreeze proteins to avoid freezing and successfully colonized their frigid habitats. The impact of the evolution of the antifreeze function on organismal success is particularly clear in the Antarctic notothenioids. This research project involves ongoing and new research on the role of antifreeze glycopeptides, antifreeze peptides and a newly discovered antifreeze potentiator protein in freezing avoidance of Antarctic fishes. The specific areas of research include: the relationship between the severity of environment and exposure of fish to ice in the water column, the uptake of endogenous ice and its fate, structure of antifreeze proteins, the molecular mechanism of antifreeze adsorption to ice and inhibition of ice crystal growth, and comprehensive analyses of the antifreeze capacity at both the protein and gene levels across the suborder Notothenioidei. Research specific to antifreeze glycopeptides includes the chromosomal locus of the gene family and its protease progenitor gene, calibration of the rate of notothenioid nuclear protein coding sequences to arrive at a more precise time estimate of the gene evolution and the temporal aspects of antifreeze glycopeptides during embryogenesis and early larval stages. The multidisciplinary approach will lead to major advances in the molecular biology and evolution of the antifreeze systems and will be applicable to a wide range of disciplines.