Functional basis of the fecundity - longevity reversal in the ant Temnothorax rugatulus

群居昆虫蜂王表现出非常长的寿命，同时也非常多产。在大多数其他动物中，这两种生活史特征是相互权衡的，也就是说，在繁殖上投入很多的个体付出了寿命缩短的代价。我们研究单位的项目旨在更深入地了解这种寿命/繁殖力逆转的最终和近似基础。这里我们关注的是蚂蚁Temnothorax rugatulus，它不仅是一个很好的模型，因为它有三种雌性种姓，易于收集和实验室维护，而且在第一期资助期间已经揭示了有趣的见解。我们可以证明，对工人的实验性生育诱导导致寿命延长，这表明即使在每个种姓中，这两种生活史特征也呈正相关。较小的微雌蜂由于代谢率较高，可以保持相同的繁殖力，但在取卵后不能提高产卵率。然而，当卵子被移除时，较大的巨卵可以增加它们的繁殖力，我们目前正在分析这是如何影响基因表达的。一项完整的转录组分析对比了年轻和年老蜂王的大脑和脂肪体，它们的繁殖力也有很大的不同，揭示了几个长寿基因的重要性，并指出了众所周知的长寿途径，如Toll和TOR信号。我们现在的目标是通过分析基因调控途径中候选基因的调控和连通性来阐明这种蚂蚁的繁殖力和寿命逆转的功能基础。为此，我们计划使用RNAi进行一些实验操作，以证明不同基因和途径之间的因果关系，并揭示候选基因对蜂王和工蜂繁殖力和寿命的影响。此外，我们将通过实验抑制组蛋白（去乙酰化）和DNA甲基化来研究调节这些途径表达的表观遗传机制。此后，我们不仅将分析这些操作如何影响蜂王和工蜂改变其繁殖力的能力，而且还将使用ChipSeq、亚硫酸氢盐测序和RNA测序来直接检查这些表观遗传过程和基因调控是如何受到影响的。我们自己的数据，特别是Bernadau & Heinze的数据表明，饮食，特别是蛋白质含量对蚂蚁的繁殖力和寿命有影响，我们计划在第二阶段对其进行操纵和研究。因此，我们的项目将涉及几个层面，重点关注两个最不同的女性种姓，工人和大女人。通过我们的综合项目，我们将有助于理解导致社会性昆虫繁殖力/寿命逆转的近似机制和最终因素。

Social insect queens exhibit extraordinarily long lifespans and at the same time are highly fecund. In most other animals, these two life history traits are traded-off, that is individuals that invest a lot in reproduction pay the price of reduced longevity. Projects in our research unit aim at gaining a deeper understanding of the ultimate and proximate basis of this longevity/fecundity reversal. Here we focus on the ant Temnothorax rugatulus, which is not only a good model due the occurrence of three females castes and its ease of collection and lab maintenance, but which already revealed interesting insights during the 1st funding period. We could show that an experimental fertility induction in workers resulted in a life-span extension indicating that the two life history traits are positively linked even within each caste. The smaller microgyne queens can maintain the same fecundity due to a higher metabolic rate, but are unable to increase egg-laying rates following egg removal. However, the larger macrogynes can increase their fecundity when eggs are removed and we are currently analyzing how this affects gene expression. A completed transcriptome analyses contrasting brain versus fat body of young and old queens, which also differed strongly in fecundity, revealed the importance of several longevity genes and pointed to well-known longevity pathways, such as Toll and TOR signaling. We now aim to elucidate the functional basis of the fecundity and longevity reversal in this ant, by analysing the regulation and connectivity of candidate genes in gene regulatory pathways. To do so, we plan a number of experimental manipulations using RNAi to demonstrate causal relationships between different genes and pathways and to reveal the effect of candidate genes on queen and worker fecundity and longevity. Moreover, we will study epigenetic mechanisms regulating expression in these pathways by experimentally inhibiting histone (de-)acetylation and DNA methylation. Thereafter, we will not only analyse how these manipulations affect the ability of queens and workers to change their fecundity, but we will also follow up with ChipSeq, Bisulfite sequencing, and RNA seq to directly check how these epigenetic processes and in turn gene regulation was affected. Our own data and especially those of Bernadau & Heinze indicate an influence of diet and in particular of the protein content on ant fecundity and longevity, which we plan to manipulate and investigate in the second phase. Our project will thus address several levels and focusses on the two most divergent female castes, workers and macrogynes. With our comprehensive project we will contribute to the understanding of the proximate mechanisms and the ultimate factors that lead to the fecundity/ longevity reversal in social insects.