Towards reconstructing the ancestral brain gene-network regulating caste differentiation in ants

Area of Science:

• Evolutionary biology
• Genomics
• Social insect biology

Background:

• Ants exhibit remarkable caste polyphenisms, with specialized reproductive queens and sterile workers.
• The evolutionary origins and genetic underpinnings of caste development across diverse ant lineages remain incompletely understood.

Purpose of the Study:

• To investigate the evolutionary conservation of gene regulatory networks underlying caste differentiation in ants.
• To identify a core set of genes consistently involved in caste development across different ant species.

Main Methods:

• Comparative brain transcriptome analysis of five ant species from three subfamilies.
• Reconstruction of gene origins and evolutionary ages (predating Neoptera vs. ant-lineage-specific).
• Analysis of caste-biased gene expression patterns and their conservation.

Main Results:

• Ancient genes predating the Neoptera were more frequently associated with queen (gyne) phenotypes.
• A conserved core gene set with consistent caste-biased expression was identified, with many genes not previously linked to caste differentiation.
• While the ancestral regulatory network is maintained, it has been modified throughout ant evolution.
• In species secondarily losing the queen caste, core regulatory genes are present but show minor expression differences between reproductive and sterile workers.

Conclusions:

• A conserved genetic toolkit plays a fundamental role in ant caste determination, originating early in insect evolution.
• Later evolutionary modifications have shaped the diversity of caste development observed in extant ant species.
• Independent evolution of castes in other social insects, like honeybees, involves different gene regulatory strategies.