Selective Pressure on Internal vs. External Immune Defence in Tribolium Castaneum - Experimental Evolution Using a Microsporidian and a Fungal Parasite

更好地了解免疫防御以及它是如何进化的是目前进化生物学中最有趣的主题之一。此外，进化免疫学与寄主寄生虫共同进化的结合将进一步加深我们的理解，因为它将免疫学从坚果壳中带回自然条件。这与最近宣布的全息组理论和微生物的重要性是一致的。然而，直到最近才被忽视的免疫防御的另一个方面是非社会有机体的外部免疫防御。外部免疫防御是一种延伸到体外的防御，例如通过行为变化或将抗微生物化合物分泌到环境中。特别是在后一种情况下，个人不仅为了自己的利益行事，而且可能也为了他们的后代和集团其他成员的利益而行事。此外，外部免疫防御和内部免疫防御应该相互作用就足够了。红粉甲虫，卡氏拟谷盗，在面粉环境中广泛地分泌抗菌物质，因此具有这种外部免疫防御。以前的工作已经证明，在自然条件下，即含有寄生虫的环境中，这种外部免疫防御与内部免疫防御是平衡的。因此，在这里提出的项目中，我问(1)外部免疫防御是否受到寄生虫的选择，不同的寄生虫是否将外部免疫防御和经典的内部免疫防御转移到不同的方向。(2)外部和内部免疫防御是如何平衡的，多个寄生虫的选择是否会导致这种平衡的破坏或稳定。(3)外部和内部免疫防御之间的平衡可能是如何调节的，如果表观遗传影响对这种平衡的影响。这将通过实验进化卡氏锥虫与微孢子虫(白色拟微孢子虫)和真菌(白僵菌)寄生虫，在三个不同的浓度和一个组合的寄生虫处理。在本实验中，将在表型水平上估计外免疫参数(苯醌分泌)和内免疫参数(酚氧化酶活性、角质层暗度、对细菌和真菌的抑制)。在实验进化之后，将采用转录和表观遗传(查看DNA甲基化、组蛋白乙酰化/去乙酰化、microRNAs)方法，以了解这一过程是如何介导的。回答这些问题将有价值地洞察生态背景下免疫防御策略的进化。

Gaining a better understanding of immune defence and how it evolves is currently one of the most interesting topics in evolutionary biology. Moreover, the combination of evolutionary immunology with host parasite co-evolution will deepen our understanding even further, as it is taking immunology out of the nut shell and back to its natural conditions. This goes in line with the recent proclamation of the hologenome theory and the importance if microbiota.However, another until only recently neglected aspect of immune defence is the external immune defence in non-social organisms. External immune defence is an extended defence outside of the body, e.g. by behavioural changes or the secretion of antimicrobial compounds into the environment. Especially in the latter case, individuals not only act to their own benefit, but potentially also to the benefit of their offspring and of other group members. Furthermore, the external immune defence should interact with the internal immune defence to be sufficient.The Red Flour Beetle, Tribolium castaneum, secrets broadly antimicrobial substances into the flour environment, and therefore possesses such an external immune defence. In previous work it has been shown, that under natural conditions, i.e. a parasite containing environment, this external immune defence is in balance with the internal immune defence. Consequently, in the here proposed project I ask(1) whether the external immune defence is under selection by parasites, and if different parasites shift external and the classical internal immune defence in different directions.(2) how external and internal immune defences are balanced, and if selection by multiple parasites will result in disruption or stabilization of this balance.(3) how the balance between external and internal immune defence might be mediated, and if epigenetic effects impact on this.This will be addressed by experimental evolution of T. castaneum with a microsporidian (Paranosema whitei) and a fungal (Beauveria bassiana) parasite, in three different concentrations each as well as a combined parasite treatment. During this experiment external (quinone secretion) and internal (Phenoloxidase activity, cuticular darkness, inhibition of bacteria and fungi) immune parameter will be estimated on the phenotypic level. Experimental evolution will be followed by transcriptomic and epigenetic (looking at DNA methylation, histone acetylation/deacetylation, microRNAs) approaches to understand how this is mediated.Answering these questions will valuable insight into the evolution of immune defence strategies in an ecological context.