Heiss Aaron A, Heiss Alaric W, Lukacs Kaleigh, Kim Eunsoo
Division of Invertebrate Zoology, American Museum of Natural History, Central Park West at 79th St., New York, New York, 10024, USA.
Sackler Institute for Comparative Genomics, American Museum of Natural History, Central Park West at 79th St., New York, New York, 10024, USA.
J Phycol. 2017 Dec;53(6):1120-1150. doi: 10.1111/jpy.12569. Epub 2017 Sep 11.
Glaucophytes are a kingdom-scale lineage of unicellular algae with uniquely underived plastids. The genus Cyanophora is of particular interest because it is the only glaucophyte that is a flagellate throughout its life cycle, making its morphology more directly comparable than other glaucophytes to other eukaryote flagellates. The ultrastructure of Cyanophora has already been studied, primarily in the 1960s and 1970s. However, the usefulness of that work has been undermined by its own limitations, subsequent misinterpretations, and a recent taxonomic revision of the genus. For example, Cyanophora's microtubular roots have been widely reported as cruciate, with rotationally symmetrical wide and thin roots, although the first ultrastructural work described it as having three wide and one narrow root. We examine Cyanophora cuspidata using scanning and transmission electron microscopy, and construct a model of its cytoskeleton using serial-section TEM. We confirm the earlier model, with asymmetric roots. We describe previously unknown and unsuspected features of its microtubular roots, including (i) a rearrangement of individual microtubules within the posterior right root, (ii) a splitting of the posterior left root into two subroots, and (iii) the convergence and termination of the narrow roots against wider ones in both the anterior and posterior subsystems of the flagellar apparatus. We also describe a large complement of nonmicrotubular components of the cytoskeleton, including a substantial connective between the posterior right root and the anterior basal body. Our work should serve as the starting point for a re-examination of both internal glaucophyte diversity and morphological evolution in eukaryotes.
灰胞藻是一类单细胞藻类，属于一个具有独特原始质体的界级谱系。蓝载藻属尤其引人关注，因为它是唯一一种在整个生命周期中都具有鞭毛的灰胞藻，这使得它的形态比其他灰胞藻更易于与其他真核鞭毛虫进行直接比较。蓝载藻的超微结构已经得到研究，主要是在20世纪60年代和70年代。然而，由于该研究自身的局限性、后续的错误解读以及该属最近的分类修订，这项工作的实用性受到了影响。例如，蓝载藻的微管根被广泛报道为十字形，具有旋转对称的宽根和细根，尽管最早的超微结构研究将其描述为有三根宽根和一根窄根。我们使用扫描电子显微镜和透射电子显微镜对尖蓝载藻进行了研究，并通过连续切片透射电子显微镜构建了其细胞骨架模型。我们证实了早期的模型，即根不对称。我们描述了其微管根以前未知和未被怀疑的特征，包括：(i) 后右根内单个微管的重新排列；(ii) 后左根分裂为两个子根；(iii) 在鞭毛器的前后子系统中，窄根与宽根的汇聚和终止。我们还描述了细胞骨架中大量的非微管成分，包括后右根与前基体之间的大量连接结构。我们的工作应作为重新审视灰胞藻内部多样性和真核生物形态进化的起点。
