Ultrastructural Complexity in Unconventional Cells

单细胞生物已经统治地球超过30亿年，但它们的特征是所有现存生物中最不为人所知的。在微生物生命的三个主要谱系中，单细胞真核生物是最复杂的。与细菌和古细菌不同，真核细胞有细胞核、膜系统、内共生获得的细胞器和复杂的细胞骨架，支持大量的特殊细胞扩展和行为。我们的研究计划旨在探索非常规的真核生物，以帮助解开跨越生命之树的谱系中的组成，相互关系和创新细胞特征。该研究旨在加速发现新的单细胞真核生物，并利用比较分子方法和高分辨率显微镜重建复杂的超微结构系统。生物学的一个中心目标是了解复杂结构的功能，以及它们是如何从更简单的前体产生的。这在比较细胞生物学领域尤其具有挑战性，因为这些研究需要复杂的技术，精细尺度的空间推理和与不熟悉的生物体相关的详细术语。形态复杂性通常与多细胞有关，如在一些动物群体中发现的照相机型眼睛。然而，一些单细胞真核生物也通过以非凡的方式排列标准的亚细胞成分获得了极其复杂的特征。例如，鞭毛藻代表了具有异常高水平细胞多样性的真核生物的主要谱系。我们的实验室已经证明，一些鞭毛藻有一种类似眼睛的“胶质”，由类似角膜、晶状体、虹膜和视网膜的亚细胞类似物组成。这些物种也有复杂的鱼叉状“刺丝囊”，其中一些使用单个加压胶囊来推进，而另一些则从类似加特林机枪的布置中独特地发射11到15枚炮弹。对这些特征的比较研究提供了一个独特的系统，可以用来追踪新的趋同案例，以及产生高度整合结构的中间阶段。对复杂超微结构性状统一性和多样性的研究主要分为四个阶段：(1)从不同环境中收集未栽培生物；(2)单细胞制备及高分辨率显微镜（CLSM、FIB-SEM、TEM）表征；(3)单细胞分离转录组学和基因组学；(4)与数字图像处理和生物信息学相关的计算分析。本研究的结果加速了对来自不同环境的真核细胞新特性的发现，并确定了单细胞生物解决运动、摄食、防御和光接受等基本问题的新方法。

Single-celled organisms have dominated the planet for over 3 billion years, yet their traits are the least understood of all extant organisms. Of the three major lineages of microbial life, single-celled eukaryotes are the most complex. Unlike bacteria and archaea, eukaryotic cells have nuclei, endomembrane systems, endosymbiotically acquired organelles and elaborate cytoskeletons supporting a vast array of specialized cell extensions and behaviors. Our research program is designed to explore unconventional eukaryotes in order to help unravel the composition, interrelationships and innovative cellular traits in lineages that span the tree of life. The research aims to accelerate the discovery of novel single-celled eukaryotes and reconstruct complex ultrastructural systems using comparative molecular methods and high-resolution microscopy. A central goal in biology is to understand the function of complex structures and how they arose from simpler precursors. This is especially challenging in the field of comparative cell biology because these studies require sophisticated technologies, spatial reasoning at a fine scale and detailed terminology associated with unfamiliar organisms. Morphological complexity is normally associated with multicellularity, as seen in the camera-type eyes found in several groups of animals. However, some single-celled eukaryotes have also acquired extremely complex traits by arranging standard subcellular components in extraordinary ways. Dinoflagellates, for instance, represent a major lineage of eukaryotes with an unusually high level of cellular diversity. Our lab has shown that some dinoflagellates have an eye-like "ocelloid" consisting of subcellular analogues to a cornea, lens, iris and retina. These same species also have intricate harpoon-like "nematocysts", some of which use a single pressurized capsule for propulsion, while others uniquely launch 11 to 15 projectiles from an arrangement similar to a Gatling gun. Comparative studies of traits like these offer idiosyncratic systems for tracing novel cases of convergence and the intermediate stages that gave rise to highly integrated structures. Research on the unity and diversity of complex ultrastuctural traits is exploratory and progresses in four principal phases: (1) collection of uncultivated organisms from diverse environments; (2) single-cell preparation and characterization using high-resolution microscopy (CLSM, FIB-SEM, TEM); (3) single-cell isolation for transcriptomics and genomics; (4) computational analyses associated with digital image processing and bioinformatics. Outcomes of this research accelerate the discovery of new traits in eukaryotic cells from diverse environments and identify novel ways in which single-celled organisms have solved basic problems, such as locomotion, feeding, defense and photoreception.