Department of Zoology, University of Oxford, South Parks Road, Oxford, OX1 3PS, UK.
Protoplasma. 2022 May;259(3):487-593. doi: 10.1007/s00709-021-01665-7. Epub 2021 Dec 23.
I thoroughly discuss ciliary transition zone (TZ) evolution, highlighting many overlooked evolutionarily significant ultrastructural details. I establish fundamental principles of TZ ultrastructure and evolution throughout eukaryotes, inferring unrecognised ancestral TZ patterns for Fungi, opisthokonts, and Corticata (i.e., kingdoms Plantae and Chromista). Typical TZs have a dense transitional plate (TP), with a previously overlooked complex lattice as skeleton. I show most eukaryotes have centriole/TZ junction acorn-V filaments (whose ancestral function was arguably supporting central pair microtubule-nucleating sites; I discuss their role in centriole growth). Uniquely simple malawimonad TZs (without TP, simpler acorn) pinpoint the eukaryote tree's root between them and TP-bearers, highlighting novel superclades. I integrate TZ/ciliary evolution with the best multiprotein trees, naming newly recognised major eukaryote clades and revise megaclassification of basal kingdom Protozoa. Recent discovery of non-photosynthetic phagotrophic flagellates with genome-free plastids (Rhodelphis), the sister group to phylum Rhodophyta (red algae), illuminates plant and chromist early evolution. I show previously overlooked marked similarities in cell ultrastructure between Rhodelphis and Picomonas, formerly considered an early diverging chromist. In both a nonagonal tube lies between their TP and an annular septum surrounding their 9+2 ciliary axoneme. Mitochondrial dense condensations and mitochondrion-linked smooth endomembrane cytoplasmic partitioning cisternae further support grouping Picomonadea and Rhodelphea as new plant phylum Pararhoda. As Pararhoda/Rhodophyta form a robust clade on site-heterogeneous multiprotein trees, I group Pararhoda and Rhodophyta as new infrakingdom Rhodaria of Plantae within subkingdom Biliphyta, which also includes Glaucophyta with fundamentally similar TZ, uniquely in eukaryotes. I explain how biliphyte TZs generated viridiplant stellate-structures.
我深入探讨了纤毛过渡区（TZ）的演化，强调了许多被忽视的具有进化意义的超微结构细节。我建立了整个真核生物的 TZ 超微结构和演化的基本原则，推断出真菌、后口动物和皮层（即植物界和 Chromista 界）未被识别的祖先 TZ 模式。典型的 TZ 具有密集的过渡板（TP），其骨架是以前被忽视的复杂晶格。我表明，大多数真核生物具有中心粒/TZ 交界处的橡子-V 丝（其祖先功能可以说是支持中心对微管成核位点；我讨论了它们在中心粒生长中的作用）。独特简单的马拉维单胞菌 TZ（没有 TP，更简单的橡子）将真核生物树的根部定位在它们和具有 TP 的生物之间，突出了新的超类群。我将 TZ/纤毛演化与最佳多蛋白树相结合，命名了新识别的主要真核类群，并修订了基础原生动物界的巨型分类。最近发现了具有无基因组质体（Rhodelphis）的非光合吞噬性鞭毛生物，它是红藻门（红藻）的姊妹群，阐明了植物和 Chromista 的早期演化。我表明，Rhodelphis 和 Picomonas 之间存在以前被忽视的显著相似的细胞超微结构，Picomonas 以前被认为是一个早期分化的 Chromista。在这两个生物中，一个八角形的管位于它们的 TP 和环绕它们的 9+2 纤毛轴丝的环形隔片之间。线粒体致密凝聚物和与线粒体相连的光滑内质网膜细胞质分隔池进一步支持将 Picomonadea 和 Rhodelphea 归类为新的植物门 Pararhoda。由于 Pararhoda/Rhodophyta 在异质多蛋白树上形成了一个强大的分支，我将 Pararhoda 和 Rhodophyta 归类为植物亚界 Biliphyta 的新的 infrakingdom Rhodaria，该亚界还包括具有基本相似 TZ 的蓝藻，这在真核生物中是独一无二的。我解释了 biliphyte TZs 如何产生了植物的星状结构。
