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，因为甜美的花朵生长得很慢……”（莎士比亚，理查三世，第二幕场景 4）生物体的生活方式存在巨大差异。例如，众所周知，蜉蝣成年后的生活和繁殖期只有 1 天，而海龟的生活和繁殖期长达数十年。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中也表现出显着的差异，并且在寿命、生长速度和繁殖持续时间方面可能存在差异。人们认为，雄性和雌性表现出截然不同的生活史可以使每种性别提高繁殖成功率。造成这种情况的最终原因源于两性在生殖投资方面的根本差异，女性通常在数量较少、较大的卵子上投资较多，而男性在数量较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一生中实现繁殖成功的不同方式。例如，预计雄性会在交配和受精方面相互激烈竞争。这可能导致高风险/高回报的“活得快、死得早”的策略，该策略需要精力充沛，因此需要高碳水化合物 (C) 饮食。另一方面，雌性有望受益于采用“活得慢，死得老”的策略，这取决于获得高蛋白（P）以支持高繁殖力和促进生存。实验与这个想法是一致的，但令人惊讶的是，我们对整个生命周期中性别特异性饮食反应对生殖成功率的影响知之甚少。我们也不了解不同性别对饮食的反应有何不同。我们本研究计划的目标是解决这些主要差距。实现后续步骤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，果蝇模型系统与“营养几何学”（以精确的 C:P 比例配制的饮食）的最新进展相结合，为解决这一差距提供了强大的工具。例如，我们可以以明确的方式改变生命历程中的饮食，生成大量群体以进行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传感途径的效果。此外，我们已经在许多代中进化出了不同 P 和 C 比例的果蝇种群，这提供了一个独特的机会来检验这些饮食是否分别有利于雌性和雄性的成功。我们的首要目标是确定饮食反应中性别差异如何以及为何发生，如下：1。我们将测试不同饮食在发育和成年期间对男性和女性生殖成功的直接影响。我们将控制具有不同C:P比率的饮食，并分别测试其对每个性别的寿命和生殖成功率的影响。2．我们将研究与性别特异性反应相关的机制。在此，我们将使用分子和遗传工具来测量改变的营养传感途径对男性和女性生殖成功的影响。3。我们将从具有暴露于高和低C和P的进化历史的品系中测量雄性和雌性的繁殖成功率。这将检验雄性与雌性成功的平衡已经进化的观点。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整个生命过程中饮食反应性别差异的后果和机制。这项工作预计将在我们对男性和女性为何以及如何表现出不同生活史的基本理解上取得重大进展。

'..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.