Lee Shu-Chuan, Liou Ming-Ru, Hsu Yau-Heiu, Wang Ing-Nang, Lin Na-Sheng
Institute of Plant and Microbial Biology, Academia Sinica, Taipei, Taiwan.
Graduate Institute of Biotechnology, National Chung Hsing University, Taichung, Taiwan.
Front Microbiol. 2023 Aug 4;14:1139447. doi: 10.3389/fmicb.2023.1139447. eCollection 2023.
Satellite RNAs (satRNAs) are molecular parasites that depend on their non-homologous helper viruses (HVs) for essential biological functions. While there are multiple molecular and phylogenetic studies on satRNAs, there is no experimental evolution study on how satRNAs may evolve in common infection conditions. In this study, we serially passaged the Bamboo mosaic virus (BaMV) associated-satRNA (satBaMV) under conditions in which satBaMV either coinfects an uninfected host plant, , with BaMV or superinfects a transgenic expressing the full-length BaMV genome. Single-nucleotide polymorphisms (SNPs) of satBaMV populations were analyzed by deep sequencing. Forty-eight SNPs were identified across four different experimental treatments. Most SNPs are treatment-specific, and some are also ephemeral. However, mutations at positions 30, 34, 63, and 82, all located at the 5' untranslated region (UTR), are universal in all treatments. These universal SNPs are configured into several haplotypes and follow different population dynamics. We constructed isogenic satBaMV strains only differing at positions 30 and 82 and conducted competition experiments in protoplasts and host plants. We found that the haplotype that reached high frequency in protoplasts and inoculation leaves also exhibited poor dissemination to systemic leaves and vice versa, thus suggesting an apparent trade-off between local replication and long-distance dissemination. We posit that the trade-off is likely caused by antagonistic pleiotropy at the 5' UTR. Our findings revealed a hitherto under-explored connection between satRNA genome replication and movement within a host plant. The significance of such a connection during satRNA evolution warrants a more thorough investigation.
卫星RNA（satRNAs）是分子寄生物，其基本生物学功能依赖于非同源辅助病毒（HVs）。虽然对satRNAs有多项分子和系统发育研究，但尚无关于satRNAs在共同感染条件下如何进化的实验进化研究。在本研究中，我们在satBaMV与竹花叶病毒（BaMV）共感染未感染宿主植物或超感染表达全长BaMV基因组的转基因植物的条件下，对与BaMV相关的卫星RNA（satBaMV）进行连续传代。通过深度测序分析satBaMV群体的单核苷酸多态性（SNP）。在四种不同的实验处理中鉴定出48个SNP。大多数SNP是处理特异性的，有些也是短暂的。然而，位于5'非翻译区（UTR）的第30、34、63和82位的突变在所有处理中都是普遍存在的。这些普遍的SNP被配置成几种单倍型，并遵循不同的群体动态。我们构建了仅在第30和82位不同的同基因satBaMV菌株，并在原生质体和宿主植物中进行了竞争实验。我们发现，在原生质体和接种叶片中达到高频的单倍型在向系统叶的传播中也表现不佳，反之亦然，因此表明在局部复制和长距离传播之间存在明显的权衡。我们认为这种权衡可能是由5'UTR处的拮抗性多效性引起的。我们的研究结果揭示了satRNA基因组复制与宿主植物内移动之间迄今未被充分探索的联系。这种联系在satRNA进化过程中的意义值得更深入的研究。
