Global Analysis of Chlorella variabilis NC64A mRNA Profiles during the Early Phase of Paramecium bursaria Chlorella Virus-1 Infection

The PBCV-1/Chlorella variabilis NC64A system is a model for studies on interactions between viruses and algae. Here we present the first global analyses of algal host transcripts during the early stages of infection, prior to virus replication. During the course of the experiment stretching over 1 hour, about a third of the host genes displayed significant changes in normalized mRNA abundance that either increased or decreased compared to uninfected levels. The population of genes with significant transcriptional changes gradually increased until stabilizing at 40 minutes post infection. Functional categories including cytoplasmic ribosomal proteins, jasmonic acid biosynthesis and anaphase promoting complex/cyclosomes had a significant excess in upregulated genes, whereas spliceosomal snRNP complexes and the shikimate pathway had significantly more down-regulated genes, suggesting that these pathways were activated or shut-down in response to the virus infection. Lastly, we examined the expression of C. varibilis RNA polymerase subunits, as PBCV-1 transcription depends on host RNA polymerases. Two subunits were up-regulated, RPB10 and RPC34, suggesting that they may function to support virus transcription. These results highlight genes and pathways, as well as overall trends, for further refinement of our understanding of the changes that take place during the early stages of viral infection.

PBCV-1/可变小球藻NC64A（Chlorella variabilis NC64A）系统是研究病毒与藻类相互作用的经典模型体系。本研究首次针对病毒复制前的感染早期阶段，开展了宿主藻类转录本的全局表达分析。在总时长逾1小时的实验周期内，约三分之一的宿主基因的标准化mRNA丰度相较未感染状态发生了显著上调或下调。发生显著转录变化的基因数量随实验推进逐步增加，直至感染后40分钟时趋于稳定。在显著上调的基因集合中，细胞质核糖体蛋白、茉莉酸生物合成途径以及后期促进复合物/周期体相关功能类别显著富集；而剪接体小核核糖核蛋白复合物与莽草酸途径相关基因则显著富集于下调基因集合中，提示上述通路在病毒感染过程中被激活或抑制。鉴于PBCV-1的转录依赖宿主RNA聚合酶，本研究还检测了可变小球藻RNA聚合酶亚基的表达情况，其中RPB10与RPC34两个亚基发生了上调，提示它们可能在病毒转录过程中发挥辅助支持作用。本研究所得结果明确了病毒感染早期发生变化的关键基因、通路及整体趋势，可为后续深化对病毒感染早期分子变化的认知提供重要参考。