COLONISATION, DOMESTICATION AND POPULATION CONTROL IN PEST INSECTS

保障世界粮食供应是一项重大挑战。因此，开发安全、环境友好和有效的防治农业重要作物病虫害的新技术具有重要意义。现有的一种非常重要的方法是昆虫不育技术(SIT)，在这种技术中，昆虫被大规模饲养，通过辐射消毒，然后大量释放。不育释放的雄性与野生雌性交配，由于这些交配不产生后代，害虫种群的数量减少。SIT的应用取得了一些巨大的成功，但也有明显的失败。为了避免已知的问题(例如，通过辐射使男性绝育造成的健康损失)，人们对基因改造(GM)技术的应用越来越感兴趣。其中之一被称为释放具有优势致命性的昆虫(RIDL)，由项目合作伙伴(Oxitec)发明。在这种情况下，雄性可以在不进行绝育的情况下被释放，被释放的个体很容易通过荧光标记在野外进行跟踪。RIDL之所以有效，是因为被释放的雄性携带着一种转基因，这种转基因会导致继承它的女儿在发育过程中死亡，这种影响可以持续几代人。这种致命性主要集中在雌性身上，因为它们在产卵时会破坏庄稼和水果。然而，一个潜在的重大障碍仍然存在。为了释放大量的害虫，害虫被驯化并在实验室设施中大规模饲养。这不可避免地选择了在实验室而不是在野外非常成功的个体(被释放的雄性必须找到野生雌性并与之交配，这项技术才能奏效)。毫不奇怪，有几个不愿与其交配的SIT雄性和/或野生雌性昆虫田间表现不佳的例子。尽管人们普遍知道这些缺点，但还没有关于用于基于SIT的方法的害虫对实验室条件的实时适应研究，以便了解并减少关键生活史特征中不必要的变化。此外，越来越清楚的是，对健康的重大贡献来自与肠道细菌的联系。在昆虫中，肠道细菌具有广泛而令人惊讶的影响，例如它们可以改变宿主的寿命、配偶选择、生殖生理、发育和新陈代谢。这种影响通常也取决于饮食，当昆虫被带进实验室，吃种类较少的食物时，肠道细菌的多样性就会减少。然而，还没有系统地研究驯化过程中肠道细菌的变化以及由此对寄主的连锁反应，例如对它们抑制害虫种群数量的能力的影响。因此，肠道细菌的变化是实验室适应的一个重要组成部分。他们对RIDL的背景特别感兴趣，在RIDL中，女性致死性的表达是通过使用饮食抗生素来控制的。作为一种副作用，这也会改变肠道微生物的作用和多样性。因此，我们需要了解宿主和他们的肠道细菌如何适应实验室大规模饲养的条件。有了这些知识，这种适应的不良影响就可以减缓或逆转。因此，主要目标是使用麦田蝇(一种世界性的重要农业害虫)来记录生活史、肠道细菌及其相互作用的变化，以及在实验室定居和实现种群抑制的能力。具体目标是：1.在不同的食物制度下，对经过30代定居的野生个体在实验室中的表现进行测试。测试1.3岁以下个体肠道细菌的相关变化。测试控制肠道细菌对在稳定或可变饮食方案下维持的个体的影响的差异。评估益生菌修复在定植期间丢失的细菌的可行性。

Safeguarding world food supplies is a grand challenge. It is therefore of great importance to develop safe, environmentally friendly and effective new techniques for tackling pests of agriculturally important crops. An existing method that has been very important is the sterile insect technique (SIT), in which insects are mass reared, sterilised by irradiation and released in large numbers. Sterile released males mate with wild females, and because these matings produce no offspring, the size of the pest population is reduced. SIT has been applied with some great successes - but also notable failures. To circumvent known problems (for example, the loss in health that results from sterilizing males with irradiation) there is increasing interest in the application of Genetic Modification (GM) technologies. One of these is known as the Release of Insects with a Dominant Lethal (RIDL), invented by the Project Partner (Oxitec). In this, males can be released without sterilization, and the released individuals are easy to track in the field via fluorescent markers. RIDL works because the released males carry a transgene that causes daughters that inherit it to die during development, an effect that can persist for several generations. The lethality is focused on females because they spoil crops and fruits when laying eggs. However, one potentially significant hurdle remains. To release large numbers, pest insects are domesticated and mass reared in laboratory facilities. This inevitably selects for individuals that are highly successful in the laboratory, rather than in the field (the released males must locate and mate with wild females for the technique to work). Unsurprisingly, there are several examples of poor field performance of SIT males and/or wild females preferring not to mate with them.Despite widespread knowledge of these drawbacks, there has been no study of adaptation to laboratory conditions for pest insects used for SIT-based approaches in real time, in order to understand, and hence minimize, unwanted changes in key life history traits. In addition, it is increasingly clear that a significant contribution to health comes from associations with gut bacteria. In insects, gut bacteria have widespread and surprising effects, e.g. they can alter host lifespan, mate choice, reproductive physiology, development and metabolism. Such effects also often depend upon diet, and the diversity of gut bacteria is diminished when insects are brought into the laboratory and eat less varied foods. However, there has also been no systematic study of changes in gut bacteria during domestication and hence the knock-on effects on hosts, e.g. on their ability to suppress pest population size. Changes to gut bacteria are therefore an important component of laboratory adaptation. They are of particular interest in the context of RIDL, in which the expression of female lethality is controlled by use of a dietary antibiotic. This will - as a side effect - also alter the effects and diversity of gut microbes.We therefore need to understand how hosts and their gut bacteria adapt to laboratory mass rearing conditions. With this knowledge, undesirable effects of such adaptation can be slowed or reversed. The main objective is therefore to use the medfly (an agricultural pest of world-wide importance) to document changes in life history, gut bacteria, and their interaction, upon colonization to the laboratory and the ability to achieve population suppression. The specific aims are:1. Test the performance of wild individuals subject to 30 generations of colonization to the laboratory, under variable food regimes.2. Test associated changes in the gut bacteria of the individuals under 1.3. Test for differences in the effects of manipulating gut bacteria on individuals maintained under either stable or variable dietary regimes.4. To assess the feasibility of probiotics to restore bacteria lost during colonization.