Abstract
The Antarctic Peninsula is one of the fastest-warming places on Earth. Elevated sea water temperatures cause glacier and sea ice melting. When icebergs melt into the ocean, it “freshens” the saltwater around them, reducing its salinity. The oceans absorb excess anthropogenic carbon dioxide (CO2) causing decline in ocean pH, a process known as ocean acidification. Many marine organisms are specifically affected by ocean warming, freshening and acidification. Due to the sensitivity of Antarctica to global warming, using biomarkers is the best way for scientists to predict more accurately future climate change and provide useful information or ecological risk assessments. The 70-kilodalton (kDa) heat shock protein (HSP70) chaperones have been used as biomarkers of stress in temperate and tropical environments. The induction of the HSP70 genes (Hsp70) that alter intracellular proteins in living organisms is a signal triggered by environmental temperature changes. Induction of Hsp70 has been observed both in eukaryotes and in prokaryotes as response to environmental stressors including increased and decreased temperature, salinity, pH and the combined effects of changes in temperature, acidification and salinity stress. Generally, HSP70s play critical roles in numerous complex processes of metabolism; their synthesis can usually be increased or decreased during stressful conditions. However, there is a question as to whether HSP70s may serve as excellent biomarkers in the Antarctic considering the long residence time of Antarctic organisms in a cold polar environment which appears to have greatly modified the response of heat responding transcriptional systems. This review provides insight into the vital roles of HSP70 that make them ideal candidates as biomarkers for identifying resistance and resilience in response to abiotic stressors associated with climate change, which are the effects of ocean warming, freshening and acidification in Antarctic organisms.
Highlights
Antarctic ice loss has accelerated at an astounding rate over the past four decades
DnaK in bacteria and HSP70s in eukaryotes are the major adenosine triphosphate (ATP)-dependent molecular chaperones that play a key role in the proteostasis network and are involved in stress response
It is undeniable that HSP70 are a vital protein family in both prokaryotes and eukaryotes due to its dominant role in maintaining a steady cellular environment under thermal and salinity stress in living organisms
Summary
Antarctic ice loss has accelerated at an astounding rate over the past four decades. The Antarctic shed ice at a rate of 40 billion tons from the year 1979–1990, and from 2009. Studies of the living responses to environmental changes have led to the importance of understanding the vulnerability of a species to stress at the molecular level by looking at its heat shock proteins (HSPs). The selective response to low temperature may be related to the increasing demand for a molecular chaperone function at low temperatures in the plant cell (Liu et al 2014) This shows that the upregulation of Hsp70s responds to other proteotoxic stressors other than heat (Feder and Hofmann 1999). The significant regulation of Hsp expression in Antarctic marine ecosystems provide good model species for studying the effects of heat, salinity, and pH stressors in the ocean. We provide some of the findings on Hsp expression level when cells were exposed to heat, salinity, and pH stress documented in a variety of organisms, focusing more on Antarctic species. DnaK act as preponderant molecular chaperones in preventing the formation of protein misfolds and aggregates that are toxic to the cells
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