Bioinformatics Center, Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto, 611-0011, Japan.
Department of Marine Science and Technology, Fukui Prefectural University, 1-1 Gakuen-cho, Obama City, Fukui, 917-0003, Japan.
Commun Biol. 2023 Jul 7;6(1):697. doi: 10.1038/s42003-023-05002-x.
The order Parmales (class Bolidophyceae) is a minor group of pico-sized eukaryotic marine phytoplankton that contains species with cells surrounded by silica plates. Previous studies revealed that Parmales is a member of ochrophytes and sister to diatoms (phylum Bacillariophyta), the most successful phytoplankton group in the modern ocean. Therefore, parmalean genomes can serve as a reference to elucidate both the evolutionary events that differentiated these two lineages and the genomic basis for the ecological success of diatoms vs. the more cryptic lifestyle of parmaleans. Here, we compare the genomes of eight parmaleans and five diatoms to explore their physiological and evolutionary differences. Parmaleans are predicted to be phago-mixotrophs. By contrast, diatoms have lost genes related to phagocytosis, indicating the ecological specialization from phago-mixotrophy to photoautotrophy in their early evolution. Furthermore, diatoms show significant enrichment in gene sets involved in nutrient uptake and metabolism, including iron and silica, in comparison with parmaleans. Overall, our results suggest a strong evolutionary link between the loss of phago-mixotrophy and specialization to a silicified photoautotrophic life stage early in diatom evolution after diverging from the Parmales lineage.
Parmales 类（Bolidophyceae 纲）是一个由小型真核海洋浮游植物组成的小类群，其细胞被硅质板包围。先前的研究表明 Parmales 是 ochrophytes 的一个成员，与硅藻（Bacillariophyta 门）是姐妹关系，硅藻是现代海洋中最成功的浮游植物群体。因此， Parmales 类的基因组可以作为参考，阐明这两个谱系分化的进化事件，以及硅藻相对于 Parmales 类更隐蔽的生活方式的生态成功的基因组基础。在这里，我们比较了 8 种 Parmales 和 5 种硅藻的基因组，以探讨它们的生理和进化差异。 Parmales 类被预测为吞噬混合营养体。相比之下，硅藻失去了与吞噬作用相关的基因，这表明它们在早期进化中从吞噬混合营养体向光合作用的生态特化。此外，与 Parmales 类相比，硅藻在涉及营养物质吸收和代谢的基因集（包括铁和硅）中表现出显著的富集。总的来说，我们的结果表明，在硅藻从 Parmales 谱系分化后，吞噬混合营养体的丧失和特化为硅化光合作用生活阶段之间存在着强烈的进化联系。
