Deformed Mediated Larval Incisor Lobe Development Causes Differing Feeding Behavior between Oriental Armyworm and...

Area of Science:

• Developmental Biology
• Insect Morphology
• Molecular Genetics

Background:

• Mandibular incisor lobes are crucial for insect feeding, influencing habits and ecological niche.
• The molecular mechanisms governing insect incisor lobe development are largely unknown.
• Two major maize pests, Mythimna separata and Spodoptera frugiperda, exhibit distinct feeding patterns linked to incisor lobe morphology.

Purpose of the Study:

• To investigate the role of the Hox gene Deformed (Dfd) in the development of mandibular incisor lobes in Mythimna separata and Spodoptera frugiperda.
• To understand how Dfd influences feeding behavior and larval survival in these two armyworm species.

Main Methods:

• Identification and expression analysis of Dfd genes in M. separata and S. frugiperda.
• RNA interference (RNAi) to knock down Dfd expression in both species.
• Observation of mandibular morphology, feeding patterns (window-feeding), and larval mortality post-knockdown.

Main Results:

• Dfd genes were identified and found to be highly expressed in the heads and eggs of both species.
• Knockdown of MsDfd in M. separata resulted in malformed mandibles lacking incisor lobes and impaired window-feeding, increasing larval mortality.
• RNAi of SfDfd in S. frugiperda did not affect mandibular development or feeding patterns, indicating species-specific roles for Dfd.

Conclusions:

• The Hox gene Dfd is essential for mandibular incisor lobe formation and normal feeding behavior in Mythimna separata.
• Dfd exhibits divergent functions in mandible development and feeding ecology between M. separata and S. frugiperda.
• This study expands the understanding of Dfd's role in insect mandible evolution and feeding adaptations.