| Symposium proposal |
| Organizer: | Wei Miao (Institute of Hydrobiology, Chinese Academy of Sciences) |
| Co-organizer: | Jie Xiong (Institute of Hydrobiology, Chinese Academy of Sciences) |
| Life on our planet appears to be dominated by higher plants and animals. Yet most of the clades in the eukaryotic tree belong to protists, a diverse collection of primarily microscopic and unicellular eukaryotes. Protists represent in excess of 100,000 species and generally fall into three categories, including the animal-like protists (also called protozoa), plant-like protists (algae), and fungi-like protists, and they may also represent the ancestors of modern-day animals, plants, and fungi. Protists exist in foliage, grass, soil, ponds, rivers, lakes, oceans, and some extreme environments. They can also be pathogens or endosymbionts of animals and plants. Therefore, they have developed specialized cell structures, organelles, pathways, and genes that adapt to their habitats. We propose a symposium on evolution of protists. Three speakers were invited to give talks. Dr. Laura A. Katz (Smith College, US) will introduce the genomics and evolution of microbial eukaryotes. Dr. Ryoma Kamikawa (Kyoto University,Japan) will introduce the diversity and evolution of eukaryotic algae. Dr. Jing Yuan (Xiamen University, China) will introduce the adaptive evolution of plasmodium. |
S24-2
Loss of photosynthesis in Ochrophyta
Ryoma Kamikawa1
1Graduate School of Agriculture, Kyoto University
Photosynthesis converts solar energy to biochemical energy, allowing particular organisms to thrive in photoautotrophic lifestyles. Photosynthetic eukaryotes have emerged multiple times independently through endosymbioses. The first photosynthetic eukaryote is thought to be the merger of a photosynthetic cyanobacterium and a heterotrophic ancestor of Archaeplastida, the former of which has given rise to the first plastid. Other photosynthetic lineages, such as chlorarachniophytes and cryptophytes, have gained plastids through eukaryote-eukaryote endosymbioses with a green alga and a red alga, respectively. Ochrophyta belonging to a large protist clade, the stramenopiles, is a photosynthetic group that has emerged by such a eukaryote-eukaryote endosymbiosis although the origin of the ochrphyte plastids remains to be elucidated. Ochrophyta includes various algal lineages that significantly contribute to oceanic ecosystems. Regardless of our view on benefits from photosynthetic autotrophic lifestyles, many species of Ochrophyta have lost photosynthesis secondarily but still retained non-photosynthetic plastids. In this presentation, I will introduce the diversity of reductive evolution of plastids through loss of photosynthesis in ochrophyte lineages. I will also discuss the genome evolution triggered by evolutionary adaptation to an osmotrophic, heterotrophic lifestyle from the photoautotrophic lifestyle in a non-photosynthetic diatom, by comparing it to the genome evolution in plastid-bearing parasites that have lost photosynthesis.
S24-3
Morphogenesis and cortical microtubule cytoskeleton in the parasitized protist Plasmodium
Jing Yuan1
1Xiamen University
Morphogenesis of many protozoans depends on a polarized establishment of cytoskeletal structures. In malaria-causing parasites, this can be observed when a round zygote develops into an elongated motile ookinete within the mosquito stomach. This morphogenesis is mediated by the pellicle cytoskeletal structures, including the inner membrane complex (IMC) and the underlying subpellicular microtubules (SPMs). How the parasite maintains the IMC-SPM connection and establishes a dome-like structure of SPM to support cell elongation is unclear. Here, we show that palmitoylation of Nterminal cysteines of two IMC proteins (ISP1/ISP3) regulates the IMC localization of ISP1/ISP3 and zygote-to-ookinete differentiation. Palmitoylation of ISP1/ISP3 is catalyzed by an IMC-residing palmitoyl-S-acyl-transferase (PAT) DHHC2. Surprisingly, DHHC2 undergoes self-palmitoylation at C-terminal cysteines via its PAT activity, which controls DHHC2 localization in IMC after zygote formation. IMC-anchored ISP1 and ISP3 interact with microtubule component b-tubulin, serving as tethers to maintain the proper structure of SPM during zygote elongation. This study uncovers a protein palmitoylation cascade regulating microtubule cytoskeleton in malaria parasites.
S24-4
The Protist 10,000 Genomes Project
Jie Xiong1, Wei Miao1, Lirong Song1, Sang Ba2, Longxian Zhang3, Guiquan Guan4, Zhang Zhang5, Kang Ning6
1National aquatic biological resource center, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, China
2Laboratory of Wetland and Catchments Ecology in Tibetan Plateau, Faculty of Natural Sciences, Tibet University, Lhasa, China
3College of animal science and veterinary medicine, Henan Agricultural University, Zhengzhou, China
4State Key Laboratory of Veterinary Etiological Biology, Key Laboratory of Veterinary Parasitology of Gansu Province, Lanzhou Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Lanzhou, China
5National Genomics Data Center, Beijing Institute of Genomics, Chinese Academy of Sciences, China National Center for Bioinformation, Beijing, China
6Department of Bioinformatics and Systems Biology, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, China
Protists are a highly diverse group of microscopic eukaryotic organisms that are not fungi, animals, or plants. The protists, which made up the Protista, was regarded as one of the five kingdoms of life. As a kingdom, only a few of protist genomes have been sequenced. There is a huge gap to understand the origin, evolution, and diversity of protists. To fill this gap, scientists in China jointly launched the Protist 10,000 Genomes Project (P10K) to generate the whole-genome sequences (WGS) of 10,000 protists and create new reference genomes for the representative species of different lineage of protists. This project will make it feasible to decipher the genome sequences of protists, reconstruct their phylogenetic tree and accordingly address fundamental scientific questions of broad interest.
S24-5
The differences between trypanosome and mammal in the perspective of centrosome/basal bodies
De-Hua Lai1
1Sun Yat-Sen University
Centriole/basal body is important organelle that plays two distinct roles in eukaryotic cells, as a microtubule organizing center and a base of building flagellum/cilium. The diversities of structure and function are briefly reviewed in this work, particularly the physical connections for its maintenance during cell cycle. Centriole/basal body (BB) connections involve two concepts – a Tether and a Linker. Studies have revealed essential components of the Tether whilst Linker components remain largely unknown. Here, we describe BBLP, a novel trypanosome protein that is a cytoskeletal component of the Linker, localizing between the BB and pro-BB throughout the cell cycle. Importantly, RNAi depletion of BBLP results in a conspicuous splitting of the BB-pBB pair subtending only the new flagellum. BBLP RNAi also perturbs mitochondrial DNA inheritance. Our data identifies BBLP as the first specific protein component of the BB/centriole Linker in eukaryotic cells. We provide a unifying model revealing how aspects of centriole/BB ontogeny and lineage can operate at different points of the cell cycle in evolutionarily diverse cells.
