DNA Sensing across the Tree of Life.

From plants to mammals, pattern recognition receptors (PRRs) specifically recognize DNA, as a potential marker of either infection or damage. These receptors play critical roles in inflammation, immunity, and pathogen resistance. Importantly, given the ubiquity of DNA, its sensing must be tightly regulated. DNA localization plays a key role in recognition, as highlighted by Toll-like receptor 9 (TLR9) in the endosomal compartment and cyclic GMP-AMP synthase (cGAS) and absent in melanoma 2 (AIM2) in the cytoplasm. Sequence and structure also enhance recognition across species. Evidence in plants supports the sensing of extracellular DNA by PRRs, leading to calcium-dependent signaling, although no receptor has been definitively identified yet. Here, we review the shared and distinct features of DNA sensors, and their physiological functions, across the tree of life.