Rhizobial tRNA-derived small RNAs are signal molecules regulating plant nodulation

Microbial tRNA pieces regulate nodulation To fix nitrogen, leguminous plants enter into a symbiotic relationship with nodulating bacteria. Ren et al. now reveal the bacteria as active regulators in this process (see the Perspective by Baldrich and Meyers). Small fragments cleaved from rhizobial tRNA molecules tap into the hosts' RNA interference machinery to silence key host genes. Thus, both host and microbe shape the symbiotic environment. Science , this issue p. 919 ; see also p. 868