Eric Kwok Hei Tang
Symbiosis is ubiquitous in our nature. Years of research focuses on understanding the fitness gain of host in intimate associations with microorganisms, and the evolution origin as well as consequences of both partners. However, not much is known about how partners were paired to deliver mutualistic effect among many other competitors, not to mention the host's mechanisms in maintaining stable associations with cooperators over time at the molecular level.
The European beewolf (Hymenopteran, Crabronidae, Philanthus triangulum) is a species of solitary, digger wasps which engage in a defensive partnership with Actinobacterium ‘Candidatus Streptomyces philanthi’ (CaSP) inside specialized antennal gland reservoirs. The bacterial symbiont is vertically transmitted and plays a decisive role in avoiding the cocoon offspring from fungal infestation of via cocktail of antibiotics production.
Previous analyses showed that the host and symbionts have become partners since 68 Mya, then co-diversified ever since with horizontal exchanges of symbionts across host species. Experimental infection of non-native bacteria into antennae of aposymbiotic female beewolves surprisingly resulted in a lack of vertical transmission. Taken together, these studies suggested some host mechanisms are maintaining a high specificity with the native symbiont. In my PhD project, these molecular bases of partner choice will be studied.
Our comparative transcriptome data has singled out some differentially expressed genes between aposymbiotic and symbiotic beewolf individuals, and preliminary testing of them pointed to some immune effectors as candidates for the partner choice of symbionts (e.g. lysozyme). A number of molecular methods, including RNAi, will be used to pinpoint the host determinant(s). Other than looking at the partner viewpoint, I will also explore the symbiont’s factor essential for colonizing the antennal gland reservoirs and elements for host recognition and vertical transmission with a state-of-the-art transposon-insertion deep sequencing.
|Bild 1||Bild 2|
The antennal gland secretion of the female European beewolf (figure 1) contains symbiotic Streptomyces (CaSP). This bacterial symbiont, stained with fluorescence probe (figure 2), can be cultured in vitro and it grows naturally in filamentous form that looks like fungus.