Mechanisms regulating nutrition-dependent developmental plasticity through organ-specific effects in insects

Area of Science:

• Developmental biology
• Evolutionary biology
• Genetics

Background:

• Nutrition is a key factor influencing animal growth and morphology.
• The insulin/insulin-like growth factor (IIS)/Target of Rapamycin (TOR) signaling pathway regulates growth and development.
• Hormonal signaling plays a crucial role in orchestrating developmental timing and organogenesis.

Purpose of the Study:

• To review recent findings on how the IIS/TOR pathway mediates the effects of nutrition on animal size and shape.
• To explore the organ-specific sensitivity of tissues to IIS/TOR signaling.
• To understand the consequences of differential tissue sensitivity on overall body morphology.

Main Methods:

• Comparative analysis of insect species, including Drosophila, dung beetles, rhinoceros beetles, and staghorn beetles.
• Review of existing literature on the IIS/TOR pathway and its role in development.
• Examination of the effects of nutrition on appendage development (horns, mandibles) versus other structures (genitalia).

Main Results:

• Nutrition, mediated by the IIS/TOR pathway, causes disproportionate growth in specific male appendages like horns and mandibles relative to body size.
• The IIS/TOR pathway's effect on growth is organ-specific, with minimal impact on structures like male genitalia in some species.
• The IIS/TOR pathway influences body size and shape by regulating metamorphic hormones such as ecdysone and juvenile hormone.

Conclusions:

• Differential tissue sensitivity to IIS/TOR signaling is a key mechanism determining organ-specific growth responses to nutrition.
• These variations in sensitivity contribute to the diversity of animal body size and shape.
• Understanding these mechanisms provides insights into the evolution of morphological adaptations.