Elevated temperatures reduce population-specific transcriptional plasticity in developing lake sturgeon (Acipenser fulvescens)

Rising mean and variance in temperatures elevates threats to endangered freshwater species such as lake sturgeon, Acipenser fulvescens. Previous research demonstrated that higher temperatures during development result in physiological consequences for lake sturgeon populations throughout Manitoba, Canada, with alteration of meta- bolic rate, thermal tolerance, transcriptional responses, growth and mortality. We ac- climated lake sturgeon (30- 60 days post fertilization, a period of high mortality) from northern and southern populations (56 degrees 02'46.5?N, 96 degrees 54'18.6?W and 50 degrees 17'52?N, 95 degrees 32'51?W, respectively, separated by approximately 650 km) within Manitoba to current (summer highs of 20- 23 degrees C) and future projected (+2- 3 degrees C) environmental temperatures of 16, 20 and 24 degrees C for 30 days, and we measured gill transcriptional responses using RNAseq. Transcripts revealed SNPs consistent with genetically distinct populations and transcriptional responses altered by acclimation tempera- ture. There were a higher number of differentially expressed transcripts observed in the southern, compared to the northern, population as temperatures increased, indicating enhanced transcriptional plasticity. Both lake sturgeon populations re- sponded to elevated acclimation temperatures by downregulating the transcription of genes involved in protein synthesis and energy production. Furthermore, there were population-specific thresholds for the downregulation of processes promoting transcriptional plasticity as well as mitochondrial function as the northern population showed decreases at 20 degrees C, while this capacity was not diminished until 24 degrees C in the southern population. These transcriptional responses highlight the molecular impacts of increasing temperatures for divergent lake sturgeon populations during vulnerable developmental periods and the critical influence of transcriptome plasticity on ac- climation capacity.

Automated summary

Increasing temperatures have detrimental effects on endangered freshwater species, such as lake sturgeon. This study demonstrates that higher temperatures during development result in physiological consequences for lake sturgeon populations, including altered metabolic rate, thermal tolerance, transcriptional responses, growth, and mortality. The research also shows population-specific thresholds for transcriptional plasticity and mitochondrial function in response to elevated temperatures, highlighting the molecular impacts of increasing temperatures on divergent lake sturgeon populations.