The influence of diet on the honeybee lipidome

驯化的蜜蜂可以说是世界上最重要的传粉者。每年，数以百万计的商业管理的蜜蜂群体为蔬菜、软果、坚果和油料作物授粉，确保了人类的粮食安全。蜜蜂还通过蜂蜜、蜂蜡和蜂王浆等其他产品为人类福利做出重要的经济贡献。在过去的15-20年里，对蜜蜂群体的集约化管理使它们更容易受到病原体和寄生虫的全球传播的影响。在一些环境中，蜜蜂暴露在令人震惊的一系列农业化学品中，包括杀虫剂、杀菌剂和除草剂。景观管理的变化减少了世界各地开花植物的多样性和丰富性，随之而来的是对蜜蜂可用的食物的影响。为了克服这些不足，养蜂人现在经常给人造花粉替代品喂食营养不平衡的食物，这会使蜜蜂容易患上痢疾等疾病。在蜜蜂集中管理的地区，所有这些因素每年都会导致严重的蜂群损失。营养对动物的健康和福利起着至关重要的作用。蜜蜂的主要营养来源是花的花粉和花蜜。花蜜提供碳水化合物，而花粉提供蛋白质、脂肪和微量营养素。许多关于蜜蜂营养的研究都集中在蛋白质的重要性上，但很少有人研究脂肪的作用。脂类是细胞膜的重要组成部分，但也用作信号分子和能量储存。动物可以从碳水化合物中重新合成脂类，但有些脂类必须从饮食中获得。这些脂肪包括必需的脂肪酸，如多不饱和脂肪酸、亚油酸和α-亚麻酸。与哺乳动物不同的是，昆虫还需要饮食中的类固醇。我们团队的一项重要发现发现，花粉中的必需脂肪酸直接影响成年工蜂的营养和行为。含有不正确数量的α-亚麻酸(即所谓的‘omega-3’)的蜜蜂表现出较差的学习能力。这种由饮食引起的行为变化可能会对蜜蜂群体产生严重影响，因为觅食的蜜蜂必须学习花卉特征才能获得花粉和花蜜。这里提出的这项研究准备对类脂在蜜蜂群体中的作用做出重要发现。我们计划调查哺乳蜜蜂食用的花粉和蜂面包中的天然脂肪是如何被吸收并转化为腺体分泌物(例如蜂王浆)喂给幼虫的。我们将量化这些脂类如何在成虫和幼蜂的组织中分布。使用我们实验室开发的先进方法和最先进的脂肪组学分析方法，我们将绘制饮食中脂肪酸和类固醇到脂肪化合物的转化图，这些化合物存在于蜜蜂的肠道、大脑、生殖器官、脂肪体和孵化的食物腺体中。我们的研究还将确定饮食中的脂肪如何影响给予幼虫的食物质量，以及饮食诱导的幼虫食物中脂肪的变化是否会影响发育。我们的最终目标将是测试饮食脂肪如何影响觅食者的寿命和整个种群在野外的表现。通过这些数据，我们将建议养蜂业使用脂肪作为花粉替代品的最佳实践。使用这些数据，土地管理者还可以选择在花粉中提供正确脂肪酸和甾醇的植物，用于农业生态系统的花带种植。基于这些原因，我们的研究将有助于改善驯化蜜蜂的福利。它有可能通过对授粉服务的影响为加强全球粮食安全作出重大贡献。

Domesticated honeybees are arguably the most important pollinators in the world. Millions of commercially-managed honeybee colonies pollinate vegetables, soft fruit, nuts and oilseed crops every year, ensuring human food security. Honeybees also make important economic contributions to human welfare through honey, wax, and other products such as royal jelly. In the past 15-20 years, intensive management of honeybee colonies has made them more vulnerable to the global spread of pathogens and parasites. In some settings, bees are exposed to a staggering array of agricultural chemicals including pesticides, fungicides and herbicides. Changes to landscape management have reduced the diversity and abundance of flowering plants throughout the world, with concomitant effects on the food available for bees. To overcome these shortages, beekeepers now routinely feed artificial pollen substitutes with unbalanced nutrition that makes bees susceptible to diseases like dysentery. All of these factors are leading to severe colony losses each year in areas where bees are intensively managed. Nutrition plays a critical role in animal health and welfare. The main source of nutrition of honeybees is floral pollen and nectar. Nectar provides carbohydrates whereas pollen provides protein, fat, and micronutrients. Many studies of bee nutrition have focused on the importance of protein, but few have examined the role of fat. Lipids are important components of cell membranes but are also used as signalling molecules and for energy storage. Animals can synthesize lipids de novo from carbohydrates, but some lipids must be acquired from diet. These lipids include essential fatty acids such as the polyunsaturated fatty acids linoleic and alpha-linolenic acid. Insects, unlike mammals, also require a dietary source of sterols. An important discovery from our team identified that the essential fatty acids found in pollen directly impact the nutrition and behaviour of adult worker honeybees. Bees with the incorrect amount of alpha-linolenic acid (so called 'omega-3') exhibit poor learning abilities. Such diet-induced changes to behaviour could have a serious impact on a bee colony, because foraging bees must learn floral traits to acquire pollen and nectar. The research proposed here is poised to make important discoveries regarding the role of lipids in a honeybee colony. We plan to investigate how natural lipids in the pollen and bee bread consumed by nursing-age worker honeybees are taken up and converted into glandular secretions (e.g. royal jelly) fed to larvae. We will quantify how these lipids are distributed within the tissues of adult and larval bees. Using advanced methods developed in our laboratories and state-of-the-art methods for lipidomic analysis, we will map the transformation of dietary fatty acids and sterols into fat compounds found in bee guts, brains, reproductive organs, fat bodies, and brood food glands. Our research will also identify how fats in diet influence the quality of food given to larvae, and whether diet-induced alterations to fat in larval food affect development. Our ultimate goal will be to test how dietary fats influence the longevity of foragers and whole colony performance in a field setting. With these data, we will advise the beekeeping industry of best practice for the use of fats in substitutes for pollen. Using these data, land managers can also choose plants that provide the correct fatty acid and sterols in pollen for flower strip planting in agroecosystems. For these reasons, our research will lead to the improvement of welfare of domesticated bees. It has the potential to make a significant contribution to the enhancement of global food security through its impact on pollination services.