Dual Single-Nucleus Gene Expression Atlas of Grapevine and Erysiphe necator During Early Powdery Mildew Infection

We applied single-nucleus transcriptomics to study how Erysiphe necator (causal agent of powdery mildew) infects grapevine leaves at one- and five- days post infection, including controls and three biological replicates. We generated a grapevine leaf atlas encompassing over 100,000 nuclei, and a pathogen atlas of more than 3,000 nuclei. We successfully annotated all major grapevine cell types, including mesophyll, epidermis, phloem and xylem parenchyma, companion cells, and guard cells. We identified key E. necator structures, including appressoria, haustoria, and hyphae, and provided a list of novel cell type markers for both species. We reveal structure-specific gene expression programs in E. necator laying a foundation for future studies of fungal development and virulence mechanisms. In the host, we identified spatially distinct expression patterns of defense-related genes. As the infection progressed, we observed the activation of a coordinated immune response involving multiple cell types, mainly epidermal and mesophyll cells. High-dimensional weighted gene co-expression network analysis identified key hubs and networks associated with cell type-specific signaling and defense response. We describe a spatial separation of pattern- and effector- triggered immunity, supporting a model in which pattern-triggered immunity is activated at the site of pathogen contact and effector-triggered immunity is induced in surrounding tissue.