A Hymenoptera-restricted gene mediating ant castes co-opts deeply conserved machinery to control organ size
Lineage-specific genes are widespread and have been implicated as phenotypic innovation inducers, but how they acquire complex developmental functions remains poorly understood. Ant queens and workers develop dramatically different organ sizes from identical genomes under juvenile hormone (JH) control, yet the molecular effectors translating JH signalling into caste-specific organ growth remain…
Recent research has uncovered a Hymenoptera-restricted gene called torch that plays a crucial role in determining ant castes and controlling organ size. This gene, which is exclusive to ants, has been found to be consistently biased towards producing gyne, or queen, traits across 68 different ant species. When knockdown experiments were conducted on virgin queens of Monomorium pharaonis, the resulting workers exhibited a multi-organ growth-restricted phenotype, demonstrating the gene's impact on caste differentiation.
The mechanism behind torch's function involves an E-box-like motif activated by the JH receptor Gce-Tai, which acts as a GA-repeat-binding transcription factor that regulates the Hippo signalling pathway. This pathway, deeply conserved in animal organ-size control, has remained unchanged for over 700 million years in various lineages lacking the torch gene.
The findings reveal that a lineage-specific gene like torch can acquire complex morphogenetic functions by co-opting ancient organ-size circuitry, offering a general route through which novel genes can drive phenotypic innovation.
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