Poor starts and silver spoons: how diet shapes sex-specific fitness from birth to death

'..我想我不会长得这么快，因为甜蜜的花朵是缓慢的。（莎士比亚《理查三世》第二幕第四场）生物体的生活方式有很大的差异。例如，众所周知，蜉蝣的生活和繁殖只有一天的成年人，而海龟的生活和繁殖几十年。然而，越来越清楚的是，同一物种的雄性和雌性在这些生活史上也可能表现出惊人的差异，并且可能在寿命、生长速度和繁殖持续时间上存在差异。人们认为，雄性和雌性表达截然不同的生活史，使每种性别都能提高其繁殖成功率。其根本原因在于两性在生殖投资方面的根本差异，女性通常在更少，更大的卵子上投资更多，而男性在数量更多的精子上投资较少。这种基本差异所产生的后果是深远的，并决定了每种性别在其一生中实现生殖成功的截然不同的方式。例如，男性被预测为在交配和受精方面相互竞争。这可能导致高风险/高回报的“活得快死得早”策略，该策略对能量要求很高，因此需要高碳水化合物（C）饮食。另一方面，女性预计将受益于采取“活得慢死老”的战略，这取决于获得高蛋白质（P），以支持高繁殖力和促进生存。实验与这一观点一致，但令人惊讶的是，我们对整个生命周期中对饮食的性别特异性反应对生殖成功的影响知之甚少。我们也不知道不同性别对饮食的反应是如何不同的。我们在这项研究计划中的目标是解决这些主要的差距。实现下一步的一个主要问题是缺乏迫切需要的直接实验测试的模型系统和操作。幸运的是，果蝇模型系统结合“营养几何学”（以精确的C：P比例配制的饮食）的最新进展，为解决这一差距提供了强大的工具。例如，我们可以以确定的方式在整个生命过程中改变饮食，生成大的队列用于生存和繁殖成功的高分辨率测试，并使用遗传和分子遗传试剂来测试操纵营养感应途径的效果。此外，我们已经在不同的P和C比率上进化了许多代的苍蝇种群，这提供了一个独特的机会来研究这些饮食是否有利于女性与男性的成功。我们的首要目标是确定如何以及为什么性别差异的饮食反应发生，如下：1。我们将测试在发育和成年期间不同饮食对雄性和雌性生殖成功的直接影响。我们将操纵不同C：P比例的饮食，并分别测试对每种性别的寿命和繁殖成功率的影响。我们将研究与性别特异性反应相关的机制。在这方面，我们将使用分子和遗传工具来测量改变的营养感应途径对男性和女性生殖成功的影响。我们将从暴露于高和低C和P的进化历史的品系中测量雄性和雌性的生殖成功。这将测试雄性与雌性成功的平衡已经进化的想法。对营养感应基因表达的测试也将揭示这些潜在途径的进化变化。这项工作将首次直接测试在整个生命过程中对饮食反应的性别差异的后果和机制。这项工作有望在我们对男性和女性为什么以及如何表现出不同的生活史的基本理解方面取得重大进展。

'..methinks I would not grow so fast, Because sweet flowers are slow ...' (Shakespeare, Richard III, Act II Scene 4)There is huge variation in the way that organisms live their lives. For example, mayflies famously live and reproduce as adults for only 1 day, while turtles live and reproduce for many decades. However, what is becoming increasingly clear is that males and females from the same species can also exhibit striking variation in these life histories, and may differ in lifespan, growth rate and duration of reproduction.It is thought that the expression of contrasting life histories by males and females allows each sex to increase their reproductive success. The ultimate reasons for this stem from fundamental differences between the sexes in reproductive investment, with females typically investing more in fewer, larger eggs and males less in their more numerous sperm. The consequences that flow from this basic difference are profound and dictate the contrasting ways in which each sex achieves reproductive success over their whole lifetimes.For example, males are predicted to compete strongly with each other for access to matings and fertilisations. This can lead to a high risk / high pay off 'live fast die young' strategy that is energetically demanding and hence requires a high carbohydrate (C) diet. On the other hand, females are expected to benefit from adopting a 'live slow die old' strategy contingent on the acquisition of high protein (P) to support high fecundity and promote survival. Experiments are consistent with this idea but we have surprisingly little insight into the effects on reproductive success of sex-specific responses to diets across the whole lifespan. Nor do we understand how each sex responds differently to diet. Our aim in this research programme is to address these major gaps.A major problem in achieving the next steps has been a lack of model systems and manipulations for the direct experimental tests that are urgently needed. Fortunately, the fruit fly model system, in combination with recent advances in 'Nutritional Geometry' (diets formulated with precise ratios of C:P) offer powerful tools to address this gap. For example, we can vary diets across the life course in a defined manner, generate large cohorts for high-resolution tests of survival and reproductive success and use genetic and molecular genetic reagents to test effects of manipulating nutrient sensing pathways. In addition, we have evolved populations of flies on different P and C ratios over many generations, which offers a unique opportunity to examine whether these diets favour the success of females versus males, respectively. Our overarching aim is to identify how and why sex differences in responses to diets occur, as follows:1. We will test the direct effect on the reproductive success of males and females of varying diets during development and adulthood. We will manipulate diets with varying C:P ratios and test the effect on lifespan and reproductive success for each sex separately.2. We will investigate the mechanisms associated with the sex-specific responses. In this we will use molecular and genetic tools to measure the impact of altered nutrient sensing pathways on male and female reproductive success.3. We will measure the reproductive success of males and females from lines with an evolutionary history of exposure to high and low C and P. This will test the idea that the balance of male to female success has evolved. Tests of the expression of nutrient sensing genes will also reveal evolved changes in these underlying pathways.The work will provide the first direct tests of the consequences and mechanisms underpinning sex differences in responses to diet across the whole life course. The work is expected to result in a major advance in our fundamental understanding of why and how males and females exhibit different life histories.