Characterization of Recombinant Plant Chromosome Fragments in Human-Arabidopsis Hybrid Cell Lines

Although plants and animals are evolutionarily distant, the structure and function of their chromosomes are largely conserved. A human-plant hybrid cell line was created previously by fusing Arabidopsis thaliana protoplasts and human HT1080 cells. This human-Arabidopsis hybrid cell line contained a neo-chromosome formed by insertion of segments of Arabidopsis chromosomes, including Arabidopsis centromere into human chromosome 15. The translocated large Arabidopsis genome fragments (~ 30 Mb) were able to maintain in the human cell background under long culture conditions. We used this unique system to investigate how the introgressed part of a plant genome was maintained in human genetic background. The analysis of the neo-chromosome in 60- and 300-day-old cell cultures by next-generation sequencing and molecular cytogenetics suggested its origin by fusion of DNA fragments of different sizes from Arabidopsis chromosomes 2, 3, 4, and 5, which were randomly intermingled rather than joined end-to-end. Although evolutionary diverged, methylation patterns in plants and animals exhibit a certain level of conservation. In this present study, we aimed to investigate the epigenetic landscape and gene expression of this large alien plant chromosomefragment in the human genome under long-term culture conditions though whole genome bisulfite sequencing. This could be a useful tool for studying the coexistence of two divergent genomes and provide insight into the fundamental principles underlying genome interactions beyond biological kingdoms.

尽管动植物在演化上亲缘关系甚远，但二者染色体的结构与功能在很大程度上具有保守性。此前已有研究通过融合拟南芥（Arabidopsis thaliana）原生质体与人类HT1080细胞，构建了人-植物杂交细胞系。该人-拟南芥杂交细胞系中存在一条新染色体，其形成方式为将包含拟南芥着丝粒（centromere）在内的拟南芥染色体片段插入人类15号染色体。易位的大型拟南芥基因组片段（约30 Mb）可在人类细胞培养环境中长期稳定存在。我们借助这一独特模型，探究植物基因组渐渗片段如何在人类遗传背景中得以维持。通过对培养60天及300天的细胞培养物使用下一代测序（next-generation sequencing）与分子细胞遗传学分析该新染色体后发现，其起源于拟南芥2、3、4、5号染色体上不同大小DNA片段的融合——这些片段并非首尾相连，而是随机交织在一起。尽管演化路径差异显著，动植物的甲基化模式仍存在一定程度的保守性。本研究通过全基因组亚硫酸氢盐测序（whole genome bisulfite sequencing），旨在探究长期培养条件下，该大型异源植物染色体片段在人类基因组中的表观遗传图谱与基因表达情况。该模型可作为研究两类差异显著基因组共存现象的有效工具，亦能为探究跨生物界基因组互作的基本原理提供新的视角。