Dual activation of UPR during prePB and PB stages. (A-B) Volcano plots showing differentially expressed genes between the cluster 2 (C2) vs clusters 1, 3 et 4 (C1-3-4) and cluster 5 (C5) vs cluster 4 (C4), respectively. Genes identified as significantly differentially expressed were colored in blue (P value <.05 and log2(fold change) >0.25). (C) Venn diagram representing genes involved in UPR and upregulated in C2 and/or C5. (D) Venn diagram of genes upregulated in C2 and/or C5. Common genes were potentially involved in UPR. (E-F) Gene set enrichment analysis showing both pathways enriched in upregulated and downregulated genes in C2 and C5 compared with C1-3-4 and C4, respectively. (G) Heat map displaying the expression of genes involved in UPR and upregulated in C2 and/or C5 for each cluster of proliferating prePB and PB, as well as quiescent MBC, PB, and PC. (H) Visualization of cells simultaneously coexpressing HSPA5 (in green) and ERN1, EIF2AK3, or ATF6 (in red) genes. Yellow dots correspond to the coexpression of the 2 genes. (I) Boxplots representing the log2 ratio of IGL and IGH read counts per cell in each cluster. (J) Plots of HSPA5 and XBP1 mRNA expression in function of pseudotime. (K) Violin plots of the main immunoglobulin genes expressed in PCs for each cluster of proliferating prePB and PB, as well as quiescent MBC, PB, and PC.