Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA 94143, USA.
Institute of Cell Biology, University of Bern, 3012 Bern, Switzerland.
Curr Biol. 2017 Feb 20;27(4):569-575. doi: 10.1016/j.cub.2016.12.057. Epub 2017 Feb 9.
The giant, single-celled organism Stentor coeruleus has a long history as a model system for studying pattern formation and regeneration in single cells. Stentor [1, 2] is a heterotrichous ciliate distantly related to familiar ciliate models, such as Tetrahymena or Paramecium. The primary distinguishing feature of Stentor is its incredible size: a single cell is 1 mm long. Early developmental biologists, including T.H. Morgan [3], were attracted to the system because of its regenerative abilities-if large portions of a cell are surgically removed, the remnant reorganizes into a normal-looking but smaller cell with correct proportionality [2, 3]. These biologists were also drawn to Stentor because it exhibits a rich repertoire of behaviors, including light avoidance, mechanosensitive contraction, food selection, and even the ability to habituate to touch, a simple form of learning usually seen in higher organisms [4]. While early microsurgical approaches demonstrated a startling array of regenerative and morphogenetic processes in this single-celled organism, Stentor was never developed as a molecular model system. We report the sequencing of the Stentor coeruleus macronuclear genome and reveal key features of the genome. First, we find that Stentor uses the standard genetic code, suggesting that ciliate-specific genetic codes arose after Stentor branched from other ciliates. We also discover that ploidy correlates with Stentor's cell size. Finally, in the Stentor genome, we discover the smallest spliceosomal introns reported for any species. The sequenced genome opens the door to molecular analysis of single-cell regeneration in Stentor.
单细胞生物 Stentor coeruleus 是研究单细胞形态发生和再生的模式生物，具有悠久的历史。Stentor [1, 2] 是一种异毛滴虫，与常见的纤毛虫模式生物（如 Tetrahymena 或 Paramecium）关系较远。Stentor 的主要区别特征是其令人难以置信的大小：单个细胞长 1 毫米。包括 T.H. Morgan [3] 在内的早期发育生物学家因其再生能力而被该系统所吸引——如果细胞的大部分被手术切除，剩余部分会重新组织成一个看起来正常但较小的细胞，具有正确的比例[2, 3]。这些生物学家还被 Stentor 所吸引，因为它表现出丰富的行为 repertoire，包括避光、机械敏感收缩、食物选择，甚至能够习惯触摸，这是一种在高等生物中通常看到的简单形式的学习[4]。虽然早期的微手术方法在这种单细胞生物中展示了一系列惊人的再生和形态发生过程，但 Stentor 从未被开发为分子模型系统。我们报告了 Stentor coeruleus 巨核基因组的测序，并揭示了基因组的关键特征。首先，我们发现 Stentor 使用标准遗传密码，这表明纤毛虫特有的遗传密码是在 Stentor 从其他纤毛虫分支出来之后出现的。我们还发现，ploidy 与 Stentor 的细胞大小相关。最后，在 Stentor 基因组中，我们发现了报告的任何物种中最小的剪接体内含子。测序基因组为 Stentor 单细胞再生的分子分析开辟了大门。
