Dynamics of Drosophila immune stress hematopoiesis assessed by single cell transcriptomics

The molecular complexity of the hematopoietic microenvironment (niche) and its response to immune stress remain largely unknown. Here, we establish the transcriptional profile of the lymph gland, the Drosophila hematopoietic organ, and its associated niche, the posterior signaling center, at single-cell resolution and at different time points following an immune challenge. Among blood cells, we identify permanent cellular states present with and without stress, but also transient states specific to the immune response, which correspond to dividing cells primed to differentiate into dedicated effector cells. The niche itself is a heterogeneous cell population, and most niche cells undergo dynamic transcriptional remodeling following immune stress. Finally, we identify two new players involved in the hematopoietic stress response: the immune deficiency pathway and the cholecystokinin-like receptor, both of which are expressed in niche cell subsets during immune stress conditions. This molecular atlas of lymph gland cells at different time points after an immune challenge provides new insights into the control of stress hematopoiesis by discrete niche cell subsets