BACKGROUND Gymnosperms represent five of the six lineages of seed plants. However, most sequenced plant mitochondrial genomes (mitogenomes) have been generated for angiosperms, whereas mitogenomic sequences have been generated for only six gymnosperms. In particular, complete mitogenomes are available for all major seed plant lineages except Conifer II (non-Pinaceae conifers or Cupressophyta), an important lineage including six families, which impedes a comprehensive understanding of the mitogenomic diversity and evolution in gymnosperms. RESULTS Here, we report the complete mitogenome of Taxus cuspidata in Conifer II. In comparison with previously released gymnosperm mitogenomes, we found that the mitogenomes of Taxus and Welwitschia have lost many genes individually, whereas all genes were identified in the mitogenomes of Cycas, Ginkgo and Pinaceae. Multiple tRNA genes and introns also have been lost in some lineages of gymnosperms, similar to the pattern observed in angiosperms. In general, gene clusters could be less conserved in gymnosperms than in angiosperms. Moreover, fewer RNA editing sites were identified in the Taxus and Welwitschia mitogenomes than in other mitogenomes, which could be correlated with fewer introns and frequent gene losses in these two species. CONCLUSIONS We have sequenced the Taxus cuspidata mitogenome, and compared it with mitogenomes from the other four gymnosperm lineages. The results revealed the diversity in size, structure, gene and intron contents, foreign sequences, and mutation rates of gymnosperm mitogenomes, which are different from angiosperm mitogenomes.

中文翻译：

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红豆杉（红豆杉科）的完整线粒体基因组：八个蛋白质编码基因已转移至核基因组。


背景技术裸子植物代表种子植物的六个谱系中的五个。然而，大多数已测序的植物线粒体基因组（线粒体基因组）都是针对被子植物生成的，而仅针对六种裸子植物生成了线粒体基因组序列。特别是，完整的线粒体基因组可用于除针叶树 II（非松科针叶树或柏树）之外的所有主要种子植物谱系，该谱系包括六个科，这阻碍了对裸子植物线粒体基因组多样性和进化的全面了解。结果在这里，我们报告了针叶树 II 中东北红豆杉 (Taxus cuspidata) 的完整线粒体基因组。与之前发布的裸子植物线粒体基因组相比，我们发现红豆杉和千岁兰的线粒体基因组单独丢失了许多基因，而苏铁、银杏和松科的线粒体基因组中全部基因均被鉴定。多个 tRNA 基因和内含子也在裸子植物的一些谱系中丢失，类似于在被子植物中观察到的模式。一般来说，基因簇在裸子植物中的保守性可能低于被子植物。此外，与其他有丝分裂基因组相比，红豆杉和千岁兰有丝分裂基因组中发现的RNA编辑位点较少，这可能与这两个物种的内含子较少和频繁的基因丢失有关。结论 我们对东北红豆杉线粒体基因组进行了测序，并将其与其他四个裸子植物谱系的线粒体基因组进行了比较。结果揭示了裸子植物有丝分裂基因组在大小、结构、基因和内含子含量、外源序列和突变率方面的多样性，这些都不同于被子植物有丝分裂基因组。