Smads and insect hemimetabolan metamorphosis.

Area of Science:

• Developmental biology
• Insect metamorphosis
• Signal transduction

Background:

• The TGF-β signaling pathway's role in hemimetabolan insect metamorphosis is largely unknown.
• Metamorphosis in insects is regulated by the MEKRE93 pathway, influenced by juvenile hormone (JH).

Purpose of the Study:

• To investigate the role of Smad factors in the metamorphosis of the German cockroach, Blattella germanica.
• To elucidate the involvement of TGF-β signaling in hemimetabolan insect development.

Main Methods:

• RNA interference (RNAi) was used to study Smad factors (Mad, Smox, Medea) in Blattella germanica.
• Analysis focused on the sixth nymphal instar (N6) stage.

Main Results:

• The BMP branch of TGF-β signaling regulates adult ecdysis and wing extension via bursicon expression.
• The TGF-β/Activin branch influences E93 expression and Krüppel homolog 1 (Kr-h1) decline, triggering adult morphogenesis.
• This branch also impacts imaginal molt timing.

Conclusions:

• Smad factors play distinct roles in Blattella germanica metamorphosis.
• TGF-β signaling is crucial for both adult ecdysis and the precise timing of metamorphic events in hemimetabolan insects.