Buchanan Justin L, Meiklejohn Colin D, Montooth Kristi L
School of Biological Sciences, University of Nebraska-Lincoln, 1104 T St, Lincoln, NE 68588-0118, USA.
Integr Comp Biol. 2018 Sep 1;58(3):591-603. doi: 10.1093/icb/icy078.
Physiological responses to short-term environmental stressors, such as infection, can have long-term consequences for fitness, particularly if the responses are inappropriate or nutrient resources are limited. Genetic variation affecting energy acquisition, storage, and usage can limit cellular energy availability and may influence resource-allocation tradeoffs even when environmental nutrients are plentiful. Here, we utilized Drosophila mitochondrial-nuclear genotypes to test whether disrupted mitochondrial function interferes with nutrient-sensing pathways, and whether this disruption has consequences for tradeoffs between immunity and fecundity. We found that an energetically-compromised genotype was relatively resistant to rapamycin-a drug that targets nutrient-sensing pathways and mimics resource limitation. Dietary resource limitation decreased survival of energetically-compromised flies. Furthermore, survival of infection with a natural pathogen was decreased in this genotype, and females of this genotype experienced immunity-fecundity tradeoffs that were not evident in genotypic controls with normal energy metabolism. Together, these results suggest that this genotype may have little excess energetic capacity and fewer cellular nutrients, even when environmental nutrients are not limiting. Genetic variation in energy metabolism may therefore act to limit the resources available for allocation to life-history traits in ways that generate tradeoffs even when environmental resources are not limiting.
对短期环境应激源（如感染）的生理反应可能会对适应性产生长期影响，特别是当反应不适当或营养资源有限时。影响能量获取、储存和利用的基因变异会限制细胞能量供应，甚至在环境营养丰富时也可能影响资源分配的权衡。在这里，我们利用果蝇的线粒体-核基因型来测试线粒体功能紊乱是否会干扰营养感应途径，以及这种干扰是否会对免疫和繁殖力之间的权衡产生影响。我们发现，一种能量受损的基因型对雷帕霉素（一种靶向营养感应途径并模拟资源限制的药物）具有相对抗性。饮食资源限制降低了能量受损果蝇的存活率。此外，这种基因型感染天然病原体后的存活率降低，并且该基因型的雌性果蝇经历了免疫-繁殖力权衡，而在具有正常能量代谢的基因型对照中并不明显。总之，这些结果表明，即使环境营养不限制，这种基因型可能也几乎没有多余的能量容量和较少的细胞营养。因此，能量代谢的基因变异可能会限制可用于分配到生活史特征的资源，即使在环境资源不限制的情况下，也会以产生权衡的方式起作用。
