A single-cell transcriptomic atlas reveals the cell differentiation trajectory and the response to virus invasion in swelling clove of garlic

The garlic bulb comprises several cloves, the swelling growth of which is significantly hindered by the accumulation of viruses. Herein, we describe a single-cell transcriptomic atlas of swelling cloves with virus accumulation, which comprised 19 681 high-quality cells representing 11 distinct cell clusters. Cells of two clusters, clusters 7 (C7) and 11 (C11), were inferred to be from the meristem. Cell trajectory analysis suggested the differentiation of clove cells to start from the meristem cells, along two pseudo-time paths. Investigation into the cell-specific activity of invasive viruses demonstrated that garlic virus genes showed relatively low expression activity in cells of the clove meristem. There were 2060 garlic genes co-expressed with virus genes, many of which showed an association with the defense response. Five glutathione synthase/reductase genes co-expressed with virus genes displayed up-regulated expression, and the glutathione and related metabolites level showed an alteration in virus-invasive garlic clove, implying the role of glutathione in viral immunity of garlic. Our study offers valuable insights into the clove organogenesis and interaction between garlic and virus at single-cell resolution.