Central molecules of termite societies

Reproductive division of labour is the hallmark of insect societies and underlies their great success. The reproducing minority, queens and kings, is highly specialized in reproduction and liberated from other activities, while the altruistic majority of helpers is devoted to work tasks and forgo its own reproduction. This organization, occurring many times independently during the social evolution, prompts a question: How does a queen (and/or a king) monopolize the reproduction and what makes the helpers forgo their own reproduction? It is extensively documented that the reproductive regulation in advanced social insects is based on chemical signals emitted by the reproductives, the primer pheromones (queen pheromones, royal pheromones, fertility signals). However, the knowledge on the identity of these “central molecules” has long been surprisingly poor, the queen pheromone of the honey bee being the only identified primer pheromone for almost half a century. Only recently, the chemistry of reproductive regulation has become a busy research field and the primer pheromones have been characterized in several other social insects. In this project, we address the chemistry of reproductive regulation in the societies of termites, using a spectrum of biological and chemical approaches.

Biogenesis of termite-produced nitro compounds

Though structurally diverse and frequent in bacteria, fungi and plants, naturally occurring nitro compounds were only very rarely documented in arthropods. (E)-1-Nitropentadec-1-ene was the first described insect-produced nitro compound, identified to be the dominant defensive chemical of termite soldiers of the genus Prorhinotermes. It is produced in very high quantities, reaching up to over 300 µg in one soldier, corresponding to more than 10% of the body mass. (E)-1-Nitropentadec-1-ene is a potent lipophilic contact poison for arthropods; its toxicity is assigned to the strong electrophilic nitroalkene group, which reacts by Michael addition with nucleophilic moieties such as sulfhydryl, hydroxyl, or amino groups. The occurrence of defensive nitro compounds in Prorhinotermes is even more intriguing when we consider its strictly xylophagous diet, very poor in nitrogen. In other words, Prorhinotermes termites produce large amounts of a rare and unexpected defensive compound made from precious nitrogen. The aim of the project is to elucidate individual steps of NPD biogenesis in Prorhinotermes soldiers, including the underlying enzymatic system.

New defensive chemicals produced by termites

Chemistry of insect defence is a fascinating research field for both, biologists and chemists. It is a real bonanza of chemicals of various functions and from various chemical classes, many of them being new to science. The societies of termites are an excellent example in this respect; nearly four hundred defensive compounds have been identified as yet to be produced by the specialized termite defenders, the soldiers. Beside an obvious function of these chemicals in direct defence against arthropod and vertebrate predators and competitors, there is increasing evidence of antibacterial and antifungal properties of the defensive secretions of soldiers. Despite the undisputable advantages of sociality, an important cost is associated with social life, i.e. the increased vulnerability to pathogens and diseases. Therefore, it is not surprising that termites possess specific defensive mechanisms against infections. These consist of behavioural and physiological adaptations and hygiene, resistance based on defensine-like peptides, mobilized by an immune response and, last but not least, external defence preventing the infection of their nests using exocrine chemicals. The aim of the project is to search for new defensive compounds produced by termite soldiers, elucidate their structure and functional significance.

Enzymes: from functional characterization to biocatalysis

We are interested in biochemical characterization of poorly known enzymes (activity determination, substrate specificity, enzyme kinetics, inhibition and activation, SDS-PAGE, zymography, structural features). In order to fully understand a biocatalytic process or design a new one, purification and structure elucidation of the enzyme is desirable. We are using a highly selective purification strategy for isolation of new proteins present in low quantities in various crude extracts and from various sources, where we search for enzymes with interesting functions and biotechnological potential. Involvement of new enzyme biocatalysts in catalytic processes is a powerful tool for the development of environmentally friendly reactions, such as enzymatically catalysed synthesis of acyclic nucleoside analogue prodrugs. In addition, the controlled modification and immobilization give us possibility to obtain the tailor made catalysts suitable for a particular process. Social insects, called sometimes "chemical factories" represent an excellent source of new enzymes underlying the great chemical diversity of their exocrine products.