Population-specific transcriptional plasticity and sub-lethal thermal thresholds in developing lake sturgeon, Acipenser fulvescens
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Date
2022-09-08
Authors
Bugg, William S
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Abstract
Changing temperatures elevate threats to physiological function in endangered freshwater species such as the lake sturgeon, Acipenser fulvescens, especially throughout vulnerable periods of early development. If temperatures breach sub-lethal thresholds, transcriptomic plasticity and acclimation capacity and a reduction of protein level responses may be diminished, increasing the vulnerability of lake sturgeon to additional environmental stressors. My thesis research investigated the effects of changing temperatures on the physiology of developing lake sturgeon from Manitoba, Canada. A common garden strategy was employed, where lake sturgeon from northern and southern populations within Manitoba were reared at equivalent and environmentally-relevant temperatures. Lake sturgeon demonstrated acclimation-specific effects on thermal tolerance related phenotypes including morphology, metabolic rate, critical thermal maximum, transcriptional responses, mortality and transcriptional responses to cold stress later in life with relative performance in many traits declining as acclimatory temperatures increased. Many of the above phenotypic responses were population-specific, with lower thermal maxima and sub-lethal thermal thresholds in the northern population of lake sturgeon. Next, I used mRNA sequencing of gill tissue and found enhanced transcriptional plasticity in the southern population relative to the less thermally tolerant northern counterparts. Pathway-specific functional analysis implicated mitochondrial function, oxidative damage, and immunocompetence as key mechanisms modulated by increasing acclimation temperatures with functional analysis indicating additional population-specific biological processes. Last, we specifically investigated the effects of sub-lethal thermal thresholds on stress and innate immune capacity through transcriptional profiling using qPCR. Acclimation temperature influenced the endocrine stress response and impaired the activation of molecular pathways involved in the immune, stress, and fatty acid responses of pathogen-challenged lake sturgeon in early development. Collective results suggest that, as environmental temperatures intensify, transcriptional plasticity, sub-lethal thermal tolerance thresholds, and overall physiological plasticity are diminished, likely resulting in the increased susceptibility of developing lake sturgeon to the effects of compounding environmental stressors.
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Keywords
Sturgeon, Thermal Stress, mRNA, Acclimation, Plasticity, Innate Immunity