Neither too much nor too little: reactive oxygen species levels regulate Drosophila hematopoiesis.

Owing to their fast diffusion, reactive oxygen species (ROS) are important tissue signalling components. High levels of ROS are generally considered as deleterious to cells. In vivo experiments in the Drosophila hematopoietic organ now challenge this view by showing that high ROS levels are intrinsically required to prime myeloid-like progenitors to differentiate.