Salinity tolerance mechanisms of an Arctic Pelagophyte using comparative transcriptomic and gene expression analysis

Area of Science:

• Microbiology
• Molecular Biology
• Arctic Ecology

Background:

• Microbial eukaryotes in the Arctic face significant short-term salinity fluctuations.
• Salinity changes are driven by sea-ice melt (low salinity) and brine channel formation (high salinity).
• Transcriptional adaptations of these organisms to such changes remain largely unknown.

Purpose of the Study:

• To investigate the transcriptional response of an ice-associated microalgae to a range of salinities.
• To identify key genes and pathways involved in salinity adaptation in Arctic microalgae.

Main Methods:

• Exposure of pelagophyte microalgae cultures to decreasing salinities from 45 to 8.
• Analysis of differential gene expression using transcriptomic approaches.
• Identification of genes related to metabolic pathways, transcription factors, protein kinases, carbohydrate active enzymes, and ion transporters.

Main Results:

• A bracketed differential gene expression response was observed with decreasing salinity.
• Overexpression of Na⁺-H⁺ antiporters and Na⁺-Pi symporters occurred as salinity decreased.
• K⁺ channel complex genes were differentially expressed at higher salinities.
• Genes for antifreeze proteins, ice-binding proteins, and acyl-esterase showed differential expression, indicating cold adaptation.

Conclusions:

• Arctic microalgae exhibit complex transcriptional strategies to cope with short-term salinity changes.
• Specific ion transport mechanisms (Na+, K+) are crucial for salinity tolerance.
• The identified genes highlight adaptations to both cold temperatures and fluctuating salinity in the Arctic environment.