Hadariová Lucia, Vesteg Matej, Hampl Vladimír, Krajčovič Juraj
Department of Parasitology, Faculty of Science, Charles University, 128 43, Prague, Czechia.
Department of Biology and Ecology, Faculty of Natural Sciences, Matej Bel University, 974 01, Banská Bystrica, Slovakia.
Curr Genet. 2018 Apr;64(2):365-387. doi: 10.1007/s00294-017-0761-0. Epub 2017 Oct 12.
Chloroplasts are generally known as eukaryotic organelles whose main function is photosynthesis. They perform other functions, however, such as synthesizing isoprenoids, fatty acids, heme, iron sulphur clusters and other essential compounds. In non-photosynthetic lineages that possess plastids, the chloroplast genomes have been reduced and most (or all) photosynthetic genes have been lost. Consequently, non-photosynthetic plastids have also been reduced structurally. Some of these non-photosynthetic or "cryptic" plastids were overlooked or unrecognized for decades. The number of complete plastid genome sequences and/or transcriptomes from non-photosynthetic taxa possessing plastids is rapidly increasing, thus allowing prediction of the functions of non-photosynthetic plastids in various eukaryotic lineages. In some non-photosynthetic eukaryotes with photosynthetic ancestors, no traces of plastid genomes or of plastids have been found, suggesting that they have lost the genomes or plastids completely. This review summarizes current knowledge of non-photosynthetic plastids, their genomes, structures and potential functions in free-living and parasitic plants, algae and protists. We introduce a model for the order of plastid gene losses which combines models proposed earlier for land plants with the patterns of gene retention and loss observed in protists. The rare cases of plastid genome loss and complete plastid loss are also discussed.
叶绿体通常被认为是真核细胞器，其主要功能是进行光合作用。然而，它们还执行其他功能，例如合成类异戊二烯、脂肪酸、血红素、铁硫簇和其他必需化合物。在拥有质体的非光合谱系中，叶绿体基因组已经减少，并且大多数（或全部）光合基因已经丢失。因此，非光合质体在结构上也已经简化。其中一些非光合或“隐蔽”质体在几十年间一直被忽视或未被识别。来自拥有质体的非光合分类群的完整质体基因组序列和/或转录组的数量正在迅速增加，从而使得预测非光合质体在各种真核谱系中的功能成为可能。在一些具有光合祖先的非光合真核生物中，未发现质体基因组或质体的任何痕迹，这表明它们已经完全失去了基因组或质体。本综述总结了目前关于非光合质体及其基因组、结构以及在自由生活和寄生植物、藻类和原生生物中的潜在功能的知识。我们引入了一个质体基因丢失顺序的模型，该模型将先前为陆地植物提出的模型与在原生生物中观察到的基因保留和丢失模式相结合。还讨论了质体基因组丢失和完全质体丢失的罕见情况。
