Opposing insulin signals underlie the same developmental switch across hemipteran insects

Area of Science:

• Evolutionary biology
• Developmental biology
• Molecular signaling

Background:

• The insulin/insulin-like signaling (IIS) pathway is widely believed to promote organ growth in metazoans.
• Understanding the evolutionary plasticity of conserved signaling pathways is crucial for deciphering developmental mechanisms.

Purpose of the Study:

• To investigate the roles of the IIS pathway in regulating organ growth, specifically wing development, in wing-dimorphic insects.
• To elucidate the molecular mechanisms by which IIS influences the switch between short and long wings.

Main Methods:

• Comparative analysis of IIS pathway gene function in firebug and planthopper species.
• Investigating the regulation of ecdysteroid biosynthesis pathway genes.
• Assessing the impact of IIS pathway modulation on wing development and hormone titers.

Main Results:

• IIS genes evolved opposing roles in wing growth regulation between firebugs and planthoppers.
• In firebugs, IIS inactivation promotes long wings; in planthoppers, IIS activation promotes long wings.
• Both activation and inactivation of IIS converge on regulating ecdysteroid titers, ultimately inducing long wing development.

Conclusions:

• The IIS pathway exhibits functional divergence in organ growth regulation across insect species.
• A conserved mechanism involving ecdysteroid titers translates opposing IIS activities into a unified developmental outcome (long wings).
• Findings challenge the traditional view of IIS as solely promoting organ growth, highlighting a negative relationship in this context.