Molecular mechanisms during food acquisition and gliding locomotion in viridiraptorid amoeboflagellates - a transcriptomic study of Orciraptor agilis (Cercozoa, Rhizaria)

绿盗龙科（Viridiraptoridae）是最近发现的一个食食性淡水鞭毛虫科，其成员具有穿透绿色藻类的细胞壁以利用其细胞内容物作为食物的能力。这些高度专业化的“原生质体饲养者”的关键能力是纤维素细胞壁聚合物的局部降解，这发生在一个明确的和物种特异性的模式。随后的食物摄取，即藻质体的提取或藻细胞的侵入，涉及细胞骨架结构和功能的变化。之间的喂养事件，移动的viridiraptorid细胞显示鞭毛为基础的滑行运动，仍然缺乏研究的运动过程中已知的鞭毛虫的不同系统发育的联系。细胞壁穿孔、被捕食细胞侵入和滑动运动是绿盗龙类中三种有趣但尚未探索的现象。因此，我打算探索1）细胞壁降解酶，2）肌动蛋白结合蛋白，3）与微管相互作用的马达蛋白在绿盗龙Orciraptor agilis。这将通过比较转录组学方法和选择的生物化学方法来完成。我的目的是阐明上述过程的基本分子机制，重点是参与细胞壁裂解的碳水化合物活性酶。有了这个建议，我希望提供实验证据，酶促细胞壁降解单细胞的“原生质体饲养员”与遗传和生物化学方法，以确定候选酶，并探讨剧目的结构和力产生细胞骨架蛋白参与喂养和运动。除了对viridiraptorids功能的具体见解外，这项工作还应有助于提高对尚未充分研究的真核超级群体Rhizaria的基因组知识。

The Viridiraptoridae is a recently discovered family of phagotrophic freshwater flagellates, whose members have the ability to penetrate the cell walls of green algae in order to exploit their cell content as food. The key ability of these highly specialised 'protoplast feeders' is the local degradation of cellulosic cell wall polymers, which takes place in a well-defined and species-specific pattern. The subsequent food uptake, i.e. the extraction of the algal plastid or the invasion of the algal cell, involves changes in cytoskeletal architecture and function. Between feeding events, mobile viridiraptorid cells display flagella-based gliding motility, a still poorly studied locomotory process known from flagellates of diverse phylogenetic affiliation. Cell wall perforation, prey cell invasion and gliding motility are three fascinating, yet unexplored phenomena in viridiraptorids. Therefore, I intend to explore 1) cell wall degrading enzymes, 2) actin-binding proteins, and 3) motor proteins interacting with microtubules in the viridiraptorid Orciraptor agilis. This will be done with a comparative transcriptomic approach and a selection of biochemical methods. My aim is to shed light on the underlying molecular machinery of the above mentioned processes with a focus on carbohydrate-active enzymes involved in cell wall lysis. With this proposal I expect to provide experimental evidence for enzymatic cell wall degradation in unicellular 'protoplast feeders' with genetic and biochemical methods, to characterise candidate enzymes, and to explore the repertoire of structural and force-generating cytoskeletal proteins involved in feeding and locomotion. Besides specific insights into the functioning of viridiraptorids, this work should also contribute to enhance genomic knowledge about the yet understudied eukaryotic supergroup Rhizaria in general.