A Nodule-Specific Protein Secretory Pathway Required for Nitrogen-Fixing Symbiosis

Abstract

Legume Symbiosome Leguminous plants (peas and beans) are major players in global nitrogen cycling by virtue of their symbioses with nitrogen-fixing bacteria that are harbored in specialized structures, called nodules, on the plant's roots. Van de Velde et al. (p. 1122 ) show that the host plant, Medicago truncatula produces nodule-specific cysteine-rich peptides, resembling natural plant defense peptides. The peptides enter the bacterial cells and promote its development into the mature symbiont. In a complementary study, D. Wang et al. (p. 1126 ), have identified the signal peptidase, also encoded by the plant, that is required for processing these specialized peptides into their active form.