Responses of the arcto-boreal krill species Thysanoessa inermis to variations in water temperature: coupling Hsp70 isoform expressions with metabolism

Abstract

Recent studies have indicated a metabolic temperature sensitivity in both the arcto-boreal krill species Thysanoessa inermis and Thysanoessa raschii that may determine these species' abundance and population persistence at lower latitudes (up to 40° N). T. inermis currently dominates the krill community in the Barents Sea and in the high Arctic Kongsfjord. We aimed to increase the knowledge on the upper thermal limit found in the latter species by estimating the CT value (19.7 °C) (critical temperature at which 50 % of animals are reactive) and by linking metabolic rate measurements with molecular approaches. Optical oxygen sensors were used to measure respiration rates in steps of 2 °C (from 0 to 16 °C). To follow the temperature-mediated mechanisms of passive response, i.e., as a proxy for molecular stress, molecular chaperone heat shock protein 70 (Hsp70) sequences were extracted from a transcriptome assembly, and the gene expression kinetics were monitored during an acute temperature exposure to 6 or 10 °C with subsequent recovery at 4 °C. Our results showed upregulation of hsp70 genes, especially the structurally constitutive and mitochondrial isoforms. These findings confirmed the temperature sensitivity of T. inermis and showed that the thermal stress took place before reaching the upper temperature limit estimated by respirometry at 12 °C. This study provides a baseline for further investigations into the thermal tolerances of arcto-boreal Thysanoessa spp. and comparisons with other krill species under different climatic regimes, especially Antarctica.

Characterization of Inducible HSP70 Genes in an Antarctic Yeast, Glaciozyma antarctica PI12, in Response to Thermal Stress

“…GaHSP70-1 and GaHSP70-2 are possibly paralogs present in the G. antarctica genome that arise by duplication, since they have a high sequence similarity and common ortholog proteins with HSP70 from other organisms. Both HSP70 proteins are diversified into heat-inducible paralogs; their functions in stress response may vary significantly from a low effect to a rapid effect and strong protein folding activities [46][47][48][49].…”

Tolerant but facing increased competition: Arctic zooplankton versus Atlantic invaders in a warming ocean

“…Our results and the findings by Smolina et al (2015) on genetic regulation in C. glacialis emphasize the absence of a thermal stress response in Arctic Calanus. For species inhabiting cold environments, several studies suggest that they accumulate heat shock proteins at a constant level to compensate for the damage associated with protein folding at low temperatures (Buckley et al, 2004;Place et al, 2004;Place and Hofmann, 2005;Huenerlage et al, 2016). This adaptation to cold temperatures results in a loss of thermal sensitivity of genes that encode such thermal stress proteins due to constantly high gene expression (Buckley et al, 2004).…”

Hypoxia Tolerance of 10 Euphausiid Species in Relation to Vertical Temperature and Oxygen Gradients

“…Both species were acclimated at a rate of 1 • C h −1 to colder and warmer temperatures for at least 12 h after completion of the 12 h post-capture acclimation. The thermal ramp steepness and amplitude took into consideration the vertical migration temperature gradient that E. hanseni experience during DVM (Werner and Buchholz, 2013) and the Arrhenius breakpoint temperature (12 • C) of T. inermis (Huenerlage and Buchholz, 2015;Huenerlage et al, 2016).…”