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Hoffmann et al. have identified Neofem4 as the gene that produces the 'royalty scent' specific to queens in Cryptotermes secundus (termite) colonies. Reproduction in female termites is limited to queens — which are identified in termite colonies by chemical signals — although the genetic interactions underlying the production of the royal scent were previously unknown.

the workers exhibited behaviour typical of queenless colonies

Social insects require a high level of communication to carry out the division of labour and cooperation that are necessary for the construction and maintenance of colonies. A previous study had identified several queen-specific genes, including Neofem4, using cDNA representational difference analysis. Neofem4, a cytochrome P450 gene, is linked to female fertility. Thus, the team hypothesized that loss of Neofem4 would result in loss of the queen scent. Although queen behaviour and health were unaffected by RNA interference (RNAi)-mediated silencing of Neofem4, the workers exhibited behaviour typical of queenless colonies. This behaviour was not seen when the queen was injected with a control short interfering RNA, which indicates that Neofem4 silencing, rather than RNAi treatment, caused this change.

To determine whether Neofem4 affected the chemical composition of the queen scent, the team analysed the chemical cuticular hydrocarbon (CHC) profile of queens and compared them to worker CHC profiles. Queens with RNAi-mediated knockdown of Neofem4 had reduced amounts of queen-specific hydrocarbons and increased amounts of worker-specific hydrocarbons, suggesting that Neofem4 directly affects queen scent.

This study provides insights into the genetic underpinnings that identify queens in termite colonies and may be representative of fertility signalling in other social insects.