Episome-Based Gene Expression Modulation Platform in the Model Diatom Phaeodactylum tricornutum

Area of Science:

• Synthetic biology
• Algal biotechnology
• Molecular genetics

Background:

• Chemically inducible gene expression systems are crucial for synthetic genetic circuits.
• Current systems in algae often rely on limited endogenous promoters responding to environmental factors.

Purpose of the Study:

• To develop a novel, efficient, tunable, and reversible episome-based transcriptional control system in the model diatom, *Phaeodactylum tricornutum*.
• To assess the dynamic range and responsiveness of these systems for synthetic biology applications in algae.

Main Methods:

• Development of an episome-based expression platform in *Phaeodactylum tricornutum*.
• Utilized a reporter protein (eYFP) to quantify gene expression dynamics.
• Assessed time- and dose-response using droplet digital PCR (ddPCR).

Main Results:

• Two inducible expression systems activated by β-estradiol and digoxin were established.
• Achieved high dynamic ranges of up to ~180-fold (β-estradiol) and ~90-fold (digoxin).
• Demonstrated tunable and reversible control, with transcriptional activation observed within minutes of inducer addition.

Conclusions:

• The developed episome-based systems offer efficient, tunable, and reversible transcriptional control in diatoms.
• This expands the synthetic biology toolkit for algae, facilitating gene discovery and metabolic engineering.
• The system is suitable for advanced synthetic genetic circuit design in algal systems.