Uncovering the molecular mechanisms underlying honest signalling in a lower termite

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Cooperatively breeding vertebrates and social insects are characterized by reproductive division of labour in which reproductives hinder offspring from reproducing often via chemical means. In ants and termites, cuticular hydrocarbons (CHCs) are supposed to function as honest signals that inform the workers about the queens fertility. There are two principle proximate mechanisms for the maintenance of honest signalling. A signal can be a handicap that is costly to produce, or it can be an index that cannot be faked, because it is causally linked to the property it is providing information about. We will test the hypothesis that queen-CHCs are an index, i.e., that the production of queen-CHCs (fertility signalling) is directly linked to molecular reproductive pathways (fertility).In the lower termite Cryptotermes secundus we recently identified a gene (Neofem4) which is essential for production of the queens CHCs. This allows unravelling the molecular pathways underlying fertility signalling in social insects for the first time. We hypothesize that Neofem4 expression is directly linked to the fertility of an individual via conserved molecular pathways (namely, the insulin-like signalling (IIS) - juvenile hormone (JH) - vitellogenin (Vg) circuit). In a combination of endocrine experiments and genetic studies we will manipulate (a) juvenile hormone titres which directly effect fertility as gonadotropic hormones, and (b) Neofem4 expression via RNA interference. By testing the effects of these manipulations on the behaviour, chemical communication and gene expression (transcriptome analyses and quantitative realtime PCR) of caste members we will uncover (a) links between fertility and Neofem4 expression and (b) pathways downstream of Neofem4 as well as potential feedback loops to fertility.This study extends the index-hypothesis of honest signalling to the molecular level and for the first time it will also be possible to test the index-hypothesis. Additionally, our work will contribute to improve our understanding how reproductive division of labour is maintained in social insects, the textbook examples for social evolution.