Wang Ruoqiu, Wu Bin, Jian Jianbo, Tang Yiwei, Zhang Ticao, Song Zhiping, Zhang Wenju, Qiong La
Tibet University-Fudan University Joint Laboratory for Biodiversity and Global Change, School of Life Sciences, Fudan University, Shanghai, China.
Key Laboratory for Biodiversity Science and Ecological Engineering, Institute of Biodiversity Science, School of Life Sciences, Fudan University, Shanghai, China.
Front Plant Sci. 2022 Dec 14;13:1051587. doi: 10.3389/fpls.2022.1051587. eCollection 2022.
(Tibetan sea-buckthorn) is one of the highest distributed woody plants in the world (3,000-5,200 meters a.s.l.). It is characterized by adaptation to extreme environment and important economic values. Here, we combined PacBio Hifi platform and Hi-C technology to assemble a 1,452.75 Mb genome encoding 33,367 genes with a Contig N50 of 74.31 Mb, and inferred its sexual chromosome. Two -specific whole-genome duplication events (18.7-21.2 million years ago, Ma; 28.6-32.4 Ma) and long terminal repeats retroelements (LTR-RTs) amplifications were detected. Comparing with related species at lower altitude, (<1, 700 meters a.s.l.), had some significantly rapid evolving genes involved in adaptation to high altitude habitats. However, comparing with (<3, 700 meters a.s.l.), no rapid evolving genes were found except microtubule and microtubule-based process genes, has a larger genome, with extra 2, 503 genes (7.5%) and extra 680.46 Mb transposable elements (TEs) (46.84%). These results suggest that the changes in the copy number and regulatory pattern of genes play a more important role for adapting to more extreme and variable environments at higher altitude by more TEs and more genes increasing genome variability and expression plasticity. This suggestion was supported by two findings: nitrogen-fixing genes of having more copies, and intact TEs being significantly closer genes than fragmentary TEs. This study provided new insights into the evolution of alpine plants.
（西藏沙棘）是世界上分布海拔最高的木本植物之一（海拔3000 - 5200米）。它具有适应极端环境的特性和重要的经济价值。在此，我们结合PacBio Hifi平台和Hi-C技术，组装了一个1452.75 Mb的基因组，该基因组编码33367个基因，Contig N50为74.31 Mb，并推断出其性染色体。检测到两次特定的全基因组复制事件（1870 - 2120万年前；2860 - 3240万年前）以及长末端重复逆转录元件（LTR - RTs）扩增。与低海拔相关物种（海拔<1700米）相比，西藏沙棘有一些参与适应高海拔栖息地的显著快速进化基因。然而，与海拔<3700米的物种相比，除了微管和基于微管的过程基因外未发现快速进化基因，西藏沙棘有更大的基因组，额外有2503个基因（7.5%）和额外680.46 Mb的转座元件（TEs）（46.84%）。这些结果表明，基因拷贝数和调控模式的变化通过更多的TEs和更多的基因增加基因组变异性和表达可塑性，在西藏沙棘适应更高海拔更极端和多变的环境中发挥了更重要的作用。这一观点得到了两个发现的支持：西藏沙棘的固氮基因有更多拷贝，完整的TEs比片段化的TEs更靠近基因。本研究为高山植物的进化提供了新的见解。
