Evolutionary History of Sexual Differentiation Mechanism in Insects

Area of Science:

• Evolutionary biology
• Molecular biology
• Genetics

Background:

• Alternative splicing generates protein diversity, crucial for eukaryotic complexity.
• The doublesex gene is a key regulator of sexual differentiation in arthropods.
• Its role in female development varies across insect groups, with its evolution remaining unclear.

Purpose of the Study:

• Investigate the ancestral function of the doublesex gene in insect evolution.
• Understand the evolutionary trajectory of doublesex in relation to female development.
• Clarify the molecular mechanisms underlying doublesex's role in sexual differentiation.

Main Methods:

• Studied doublesex gene expression and function in Thermobia domestica (Zygentoma).
• Analyzed sex-specific isoforms and their necessity for sexual morphology.
• Reconstructed ancestral doublesex sequences and predicted protein structures.

Main Results:

• In T. domestica, doublesex is essential for male differentiation but not female.
• T. domestica doublesex shows a short female-specific region and upregulates vitellogenin in females.
• Ancestral sequence reconstruction revealed an extended C-terminal disordered region in holometabolan doublesex isoforms.

Conclusions:

• The doublesex gene initially promoted male differentiation in insects.
• Early doublesex function in female morphogenesis is suggested by T. domestica findings.
• Acquisition of female development function likely involved protein motif structural changes rather than new exon emergence.