Comparative genomics of a unique mutualistic apicomplexan

 描述(由申请人提供) Apicomplexa是一组单细胞生物体，长期以来一直被认为是唯一的寄生支系。有许多生态和医学上重要的尖端复合体，包括疟疾的病原体。然而，最近的证据揭示了一组互惠共生的顶端复合体：海洋共生菌属，肾霉菌。肾霉菌在许多方面都是不同寻常的顶端复合体。首先，这个属的成员只在一个海鞘家族中被发现，在那里它们定居在一个巨大的、无导管的器官--肾囊中。在这个器官中，尿酸和草酸钙沉淀物周围有肾霉菌。其次，对于顶端复合体来说，肾霉菌细胞中含有胞内细菌，这是不寻常的。这种互惠的顶端复合体为解决有关顶端复合体生物学的重要问题提供了一个难得的机会。我们的长期目标是完整地描述这个系统，这里我们建议重点比较肾霉菌的基因组和它的近亲，寄生属，心脏孢子虫。心孢子虫的成员寄生在广泛的海鞘中，但像肾脏霉菌一样，也含有内生细菌。同时栖息于肾霉菌和心孢子虫的细菌的基因组也将被测序。数据生成将强调这样一个假设，即细菌共生体可能在这种互惠关系的演变中提供关键的代谢功能。这些生物的基因组序列将为细胞学、显微镜和功能基因组研究提供垫脚石。了解Apicomplexa中生活方式转变的基因组特征将对确定哪些基因组特征与毒力和寄生相关具有重大影响，但尚未得到充分认识。

 DESCRIPTION (provided by applicant) Apicomplexa is a group of unicellular organisms that has been long been considered an exclusively parasitic clade. There are many ecologically and medically important apicomplexans, including the causative agent of malaria. However, recent evidence has revealed one group of mutualistic apicomplexans: the marine symbiont genus, Nephromyces. Nephromyces are unusual apicomplexans in many ways. First, members of this genus are found exclusively inside one family of sea squirts, where they colonize a large, ductless organ, the renal sac. Within this organ, Nephromyces surround urate and calcium oxalate deposits. Second, unusually for apicomplexans, Nephromyces cells contain intracellular bacteria. This mutualistic apicomplexan offers a singular opportunity to address the important question about apicomplexan biology. With a long-term goal of completely characterizing this system, here we propose to focus on comparing the Nephromyces genome to its closest relative, the parasitic genus, Cardiosporidium. Members of Cardiosporidium parasitize a broad range of sea squirts yet, like Nephromyces, also contain endosymbiotic bacteria. The genomes of the bacteria inhabiting both Nephromyces and Cardiosporidium will also be sequenced. Data generation will have an emphasis on the hypothesis that the bacterial symbionts may provide key metabolic functions in the evolution of this mutualism. The genome sequences from these organisms will provide a stepping-stone for cytological, microscopy and functional genomic research. Understanding the genomic signatures of lifestyle transitions in Apicomplexa will have significant impact on determining which, as yet underappreciated, genomic features are correlated with virulence and parasitism.