The complete chloroplast and mitochondrial genomes of Charophyta have shed new light on land plant terrestrialization. Here, we report the organellar genomes of the Zygnema circumcarinatum strain UTEX 1559, and a comparative genomics investigation of 33 plastomes and 18 mitogenomes of Chlorophyta, Charophyta (including UTEX 1559 and its conspecific relative SAG 698-1a), and Embryophyta. Gene presence/absence was determined across these plastomes and mitogenomes. A comparison between the plastomes of UTEX 1559 (157 548 bp) and SAG 698-1a (165 372 bp) revealed very similar gene contents, but substantial genome rearrangements. Surprisingly, the two plastomes share only 85.69% nucleotide sequence identity. The UTEX 1559 mitogenome size is 215 954 bp, the largest among all sequenced Charophyta. Interestingly, this large mitogenome contains a 50 kb region without homology to any other organellar genomes, which is flanked by two 86 bp direct repeats and contains 15 ORFs. These ORFs have significant homology to proteins from bacteria and plants with functions such as primase, RNA polymerase, and DNA polymerase. We conclude that (i) the previously published SAG 698-1a plastome is probably from a different Zygnema species, and (ii) the 50 kb region in the UTEX 1559 mitogenome might be recently acquired as a mobile element.

中文翻译：

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Zygnema circumcarinatum UTEX 1559叶绿体和线粒体基因组提供了对陆地植物进化的了解。

芦苇的完整叶绿体和线粒体基因组为陆地植物的陆地化提供了新的思路。在这里，我们报告了圆环Z虫（Z​​ygnema circumcarinatum）的细胞器基因组菌株UTEX 1559，以及对33个质体和18个有丝分裂基因组（包括UTEX 1559及其同种相对SAG 698-1a）和胚状体的有丝分裂基因组的比较基因组学研究。在这些质体组和有丝分裂组中确定基因的存在与否。UTEX 1559（157 548 bp）和SAG 698-1a（165 372 bp）的塑性组之间的比较显示出非常相似的基因含量，但是基因组重排。令人惊讶的是，两个质体组仅共享85.69％的核苷酸序列同一性。UTEX 1559的有丝分裂基因组大小为215954 bp，在所有测序的Charophyta中最大。有趣的是，这个大的有丝分裂基因组包含一个50 kb的区域，与任何其他细胞器基因组都没有同源性，其两侧是两个86 bp的直接重复序列，并包含15个ORF。这些ORF与来自细菌和植物的蛋白质具有显着的同源性，并具有诸如引发酶，RNA聚合酶和DNA聚合酶的功能。我们得出的结论是：（i）先前发布的SAG 698-1a质体组可能来自其他Zygnema物种，以及（ii）UTEX 1559丝分裂基因组中的50 kb区域可能最近已作为一种移动元件获得。