Transcriptional interference gates monogenic odorant receptor expression in ants

Area of Science:

• Molecular Biology
• Neuroscience
• Genetics
• Animal Behavior

Background:

• Ant communication relies heavily on olfaction, facilitated by an expanded repertoire of odorant receptor (OR) genes.
• Ant OR genes are organized in large genomic arrays, but the mechanism for expressing only one OR per neuron is unknown.
• Existing research shows only one OR mRNA is functional in the cytoplasm, while others remain nuclear.

Purpose of the Study:

• To elucidate the regulatory mechanism controlling the expression of single functional odorant receptors (ORs) from large genomic arrays in ants.
• To investigate the role of transcription directionality and non-coding RNAs in OR gene regulation.
• To determine if this regulatory mechanism is conserved in other insect species.

Main Methods:

• Analysis of gene expression patterns in ant olfactory sensory neurons (OSNs).
• Investigation of readthrough transcription and bidirectional promoter activity.
• Identification and characterization of antisense long non-coding RNAs.
• Comparative analysis of OR gene regulation in ants and bees.

Main Results:

• Readthrough transcription in the downstream direction produces non-translated transcripts.
• Ant OR promoters are bidirectional, generating antisense long non-coding RNAs.
• Bidirectional transcription, not readthrough or antisense RNAs, appears critical for suppressing other OR genes in an array.
• Evidence suggests this regulatory mechanism is conserved across ants and bees.

Conclusions:

• Bidirectional transcription is the key mechanism suppressing expression of all but one odorant receptor (OR) gene in an array.
• This ensures functionally monogenic OR expression in OSNs.
• The conserved regulatory architecture across ants and bees indicates a widespread mechanism for OR gene regulation in insects with expanded OR repertoires.