Sexual reproduction in the livestock pathogen Trypanosoma congolense

锥虫病是一种主要的牲畜疾病，它在历史上通过摧毁耕畜和生产动物而削弱了撒哈拉以南非洲的农业发展。这种由采采蝇传播的疾病继续严重限制非洲许多国家的畜牧业生产，因为这种疾病非常普遍，影响到大多数主要牲畜物种，包括牛、绵羊、山羊、猪、马、驴和骆驼。兽医几乎没有药物可用于预防或治疗，耐药性正在增加和广泛;没有疫苗。气候变化可能会加剧动物锥虫病的问题，该疾病已经影响到温带以及热带和亚热带地区。该疾病是由被称为锥虫的微观单细胞生物引起的，在受影响牲畜的血液中发现了这种生物。我们研究的目标是找出锥虫如何在它们之间交换遗传物质，以及这是否会产生具有新特征的新型寄生虫。基因交换使基因通过细胞间的转移在细胞群中快速传播。这在病原微生物的情况下尤其重要，因为一旦出现耐药性基因，它就可以迅速传播，使以前有效的药物变得无用。因此，具有性周期的微生物可能比无性繁殖的微生物更难控制。在这里，我们将应用我们从布氏锥虫的研究中获得的知识和技能，这是人类锥虫病的责任，调查T。congolense，一种相关的牲畜病原体。这两种锥虫都由采采蝇携带，但有显著差异：布氏杆菌在苍蝇唾液腺中发育，已知布氏杆菌在此处进行有性繁殖，形成新的杂交菌株;刚果果蝇在其叮咬和进食器官中发育，但我们至今不知道它是否也能在那里进行有性繁殖。然而，有证据表明，T。从非洲收集的菌株的遗传比较来看，刚果红在自然种群中确实发生了遗传交换。我们以前开发了一种实验装置，通过混合发不同颜色（红色和绿色）荧光的锥虫菌株，直接在采采蝇中识别杂交锥虫。红色和绿色荧光的组合产生黄色荧光，因此任何杂交锥虫都可以与两个亲本区分开。我们计划利用这一系统来研究T.实验室里的刚果人对于T. brucei，这对识别杂交种以及它们在果蝇中的位置至关重要，这样我们就可以寻找真正交配的细胞-配子。卵子和精子是人类的配子，但在T。布鲁塞的配子都是一种细胞。配子是由一种特殊的细胞分裂方式产生的，这种分裂方式被称为减数分裂。为了鉴定这些减数分裂细胞，我们将使用荧光报告基因来跟踪减数分裂特异性蛋白的表达。刚果人有这些蛋白质的基因。减数分裂细胞的鉴定将引导我们找到配子;在交配过程中，这些细胞融合在一起，交换DNA和细胞质。我们希望能在T. congolense和T.我们开发了所有的工具和方法，我们需要为这个项目的相关寄生虫，T。brucei，因此将这些应用于T.因此，我们的项目有很大的成功机会。到项目结束时，我们将确定是否T。这对有害基因在这种重要家畜寄生虫的不同菌株之间的传播具有深远的意义。

Trypanosomiasis is a major livestock disease that historically crippled the development of agriculture in sub-Saharan Africa by destroying both draught and production animals. This tsetse fly-transmitted disease continues to severely constrain livestock production in many countries in Africa, because it is very widespread and affects most of the major livestock species, including cattle, sheep, goats, pigs, horses, donkeys and camels. Vets have few drugs available for prophylaxis or treatment, and drug resistance is increasing and widespread; there is no vaccine. Climate change is likely to exacerbate the problem of animal trypanosomiasis, which already affects temperate as well as tropical and subtropical regions.The disease is caused by microscopic, single-celled organisms called trypanosomes, which are found in the blood of affected livestock. The goal of our research is to find out how trypanosomes swap their genetic material among themselves and whether this generates novel types of parasite with new features. Genetic exchange enables the rapid spread of genes through a cell population by transfer from cell to cell. This is particularly important in the case of pathogenic microbes, because once a gene for drug resistance has arisen, it can quickly spread, rendering a previously effective drug useless. A microbe with a sexual cycle is therefore potentially more difficult to control than one that reproduces asexually. Here we will apply the knowledge and skills we have gained from our studies of Trypanosoma brucei, which is responsible for human trypanosomiasis, to investigate sexual reproduction in T. congolense, a related livestock pathogen. Both these trypanosomes are carried by tsetse flies, but with significant differences: T. brucei develops in the fly salivary glands and this is where it is known to undergo sexual reproduction with formation of novel hybrid strains; T. congolense develops in the fly's biting and feeding apparatus, but as yet we have no knowledge of whether it can also undergo sexual reproduction there. There is, however, evidence that T. congolense does undergo genetic exchange in natural populations from genetic comparisons of strains collected in Africa. We previously developed an experimental setup to identify hybrid trypanosomes directly in tsetse flies by mixing trypanosome strains that fluoresced with different colours, red and green. The combination of red and green fluorescence yields yellow fluorescence, so that any hybrid trypanosome can be distinguished from both parents. We plan to use this system to investigate sexual reproduction in T. congolense in the laboratory. For T. brucei, this was crucial in identifying hybrids and where they occurred in the fly, so we could then search for the cells that actually mate - the gametes. Eggs and sperm are the gametes in humans, but in T. brucei the gametes were all a single kind of cell. The gametes are produced by a special form of cell division called meiosis. To identify these meiotic cells, we will use fluorescent reporter genes to track expression of meiosis-specific proteins; we already know that T. congolense has the genes for these proteins. Identification of the meiotic cells will lead us to the gametes; during mating, these cells fuse together and exchange DNA and cytoplasm. We expect to find major differences in the meiotic cells and gametes of T. congolense and T. brucei, based on their known developmental cycles.We developed all the tools and approaches we need for this project for the related parasite, T. brucei, so it is relatively straightforward to apply these to T. congolense, and our project thus has a high chance of success. By the end of the project we will have established whether T. congolense can undergo mating and how it does it. This has profound implications for the spread of harmful genes among different strains of this important livestock parasite.