Strong GAL4 expression compromises Drosophila fat body function.

Area of Science:

• Genetics
• Molecular Biology
• Immunology

Background:

• Transgenic protein overexpression is crucial for biological discoveries in model organisms like Drosophila melanogaster.
• However, the unintended physiological impacts of these transgenes are often overlooked.

Purpose of the Study:

• To investigate the physiological consequences of the yolk-GAL4 transgene in Drosophila.
• To determine if other transgenes expressed in the fat body can similarly affect fly physiology and immunity.

Main Methods:

• Utilized the yolk-GAL4 Drosophila line to express the GAL4 transcription factor in the fat body.
• Assessed physiological parameters including lipid stores, egg production, and resistance to bacterial infection.
• Employed RNA interference (RNAi) to knockdown GAL4 expression.
• Constructed new fly lines expressing nuclear-localized mCherry and LexA transactivators.

Main Results:

• Yolk-GAL4 expression disrupted fat body integrity, reduced lipid stores, impaired egg production, and decreased resistance to bacterial infections.
• GAL4 knockdown fully rescued these defects, confirming the transgene's role.
• Higher GAL4 expression correlated with increased infection susceptibility.
• Nuclear-localized mCherry and LexA also increased infection susceptibility, suggesting intranuclear proteins can impair immune response.

Conclusions:

• The GAL4 transgene product, when expressed strongly in the Drosophila fat body, induces significant physiological defects.
• Intranuclear transgenes, depending on expression strength, can impair the fat body's immune response.
• Rigorous characterization of genetic tools is essential for accurate interpretation of results in model systems.