Untersuchungen zur Entschlüsselung des molekularen Mechanismus ehrlicher Signale bei einer niederen Termite
Evolution, Anthropologie
Zusammenfassung der Projektergebnisse
In social species, from helper systems in birds and mammals to many social insects, often only one pair or a single female reproduces (queens) who prevent other group/colony members from having own offspring. Theoretical considerations for termites suggest that such reproductive inhibition is in the evolutionary interest of non-reproducing workers - and the queens - as long as the queens are fertile. Thus, we expect that mechanisms have evolved which honestly indicate the fertility of queens and which are assessed by workers (i.e., evolution of honest fertility signalling). In ants and termites, hydrocarbons on the cuticle of insects (cuticular hydrocarbons, CHCs) are strong candidates of such fertility signalling. One mechanism for the maintenance of honest signalling is that the signal (then called index) cannot be faked because it is causally linked to the property it is providing information about. Our project aimed at testing the hypothesis that queen-CHCs are an index, i.e., that the production of queen-CHCs (fertility signalling) is directly linked to molecular pathways underlying reproduction (fertility). We had one candidate gene, Neofem4, that might function as a fertility index gene. We tested this hypothesis in the termite Cryptotermes secundus by performing experiments in which we manipulated fertility-related hormones and silenced candidate genes via RNA interference. We analysed the consequences of these manipulations on (i) the behaviour of termites, (ii) hormone titres, (iii) gene expression, and (iv) chemical CHC signals. We could identify a single molecular network of co-expressed genes, called Queen Central Module (QCM), underlying hormone production, fertility, and chemical CHC production. We revealed that our initially proposed fertility index gene, Neofem4, seems to be upstream in this gene cascade, potentially involved in regulating the whole gene network. We identified a further gene which fulfils all criteria to function as fertility index gene. This gene is the central - hub - gene of the QCM. Its expression seems directly linked to fertility hormones and fertility, and it affects CHC fertility signals. Our work uncovered major genes and a network of co-expressed genes underlying the queen phenotype and chemical communication. Furthermore, linking fertility with fertility signalling is a major step forward in determining the mechanisms underlying reproductive division of labour, the hallmark of insect societies. Finally, our project was able to extend the ‘index-hypothesis’ of honest signalling to the molecular level and it provided, for the first time, strong support for the existence of honest fertility index genes.
Projektbezogene Publikationen (Auswahl)
- (2018) Chemical fertility signaling in termites: idiosyncrasies and commonalities in comparison with ants. Journal of Chemical Ecology 44:818-826
Korb J
(Siehe online unter https://doi.org/10.1007/s10886-018-0952-2) - (2021) Transcriptomic analyses of the termite, Cryptotermes secundus, reveal a gene network underlying a long lifespan and high fecundity. Communications Biology 4:384
Lin S, Werle J, Korb J
(Siehe online unter https://doi.org/10.1038/s42003-021-01892-x)
