寄生植物菟丝子线粒体基因组介导的水平基因组转移研究

There are ~2,000 species of natural parasitic plants in the world, they rarely or do not carry out Photosynthesis themselves and acquire most nutriments from their host plants. Some latest studies showed that some parasitic plants, like some in the Cuscuta genus, would gain not only water and nutriments, but also genetic materials (genomic sequences) from their hosts. The proposer found in her previous study for the first time that the mitochondrial genomes of three Cuscuta australis individuals parasitizing on three different host plants had inordinately acquired the chloroplast genomes of their hosts respectively. Combined with this result, the proposer raised a hypothesis that the mitochondrial genome of C. australis acquired extraneous genomic sequences from its host via genome recombination to facilitate the horizontal genome transfer from host to parasite during the process of its parasitizing. To testify this hypothesis in this study, we plan to collect about 20 typical sample sets of C. australis parasitizing different host plants in the field, sequence and analyze their mitochondrial genomes to study the means and common characters of C. australis acquiring extraneous genes and sequences, in order to further determine this new mechanism of horizontal genome transfer between species mediated by plant mitochondrial genomes and provide new insights into the interactions between parasites and their host plants as well as into horizontal sequence exchanges among plants.

自然界中约有2,000多种寄生植物，它们自身很少进行或者不进行光合作用，而是依靠从宿主获得营养物质来维持自身的生长繁殖。最新研究结果表明，菟丝子等寄生植物在寄生生长的过程中，不仅会从宿主植株上吸取水分和营养物质，还会获取一些遗传物质（基因序列）。申请人在前期工作中首次发现，寄生于3种不同宿主的南方菟丝子，其线粒体基因组竟然不同程度地获得了这3种宿主植物的叶绿体基因组序列。结合该发现，申请者提出假设：南方菟丝子在侵染宿主植物的过程中，其线粒体基因组会通过基因组重组的方式获得宿主的基因组序列，从而促进菟丝子与宿主之间的水平基因组转移。为进一步检验以上假说，本研究计划从野外采集20份左右寄生于不同代表性宿主的南方菟丝子材料，对其线粒体基因组进行测序和组装分析，研究其获取外来序列的方式和共性，进而解析植物线粒体基因组介导的物种间水平基因组转移新机制，也为寄生植物与宿主间的水平基因交流提供新的借鉴。

菟丝子是一种寄生植物，它们自身很少进行或者不进行光合作用，而是依靠从宿主获得营养物质来维持自身的生长繁殖。最新研究结果表明，菟丝子等寄生植物在寄生生长的过程中，不仅会从宿主植株上吸取水分和营养物质，还会获取一些遗传物质(基因序列)。本研究拟从野外选择寄生于不同类群、不同生境宿主植物的菟丝子材料作为代表，对其进行线粒体基因组的测序和组装分析，分析菟丝子侵染宿主植物过程中其线粒体获取外缘基因的种类、比例和序列特征。研究中首次获得完整的菟丝子线粒体基因组序列。经过基因组组装分析，发现南方菟丝子完整线粒体基因组为环状、大小约 500 kb 左右，包含有约 30 多个功能基因(蛋白质编码基因、转运 RNA、核糖体 RNA)。基因组中大部分(>90%)序列为重复序列。一般而言，同一种植物的线粒体基因组序列是保持不变的。然而，通过对寄生于不同植物的南方菟丝子线粒体基因组进行分析之后发现，随着寄主植物的不同，菟丝子线粒体基因组也发生了大量的序列变异。我们的研究为寄生植物线粒体基因组变异提供了新的借鉴。