Effector biology during biotrophic invasion of plant cells

Chaudhari, Prateek; Ahmed, Bulbul; Joly, David L; Germain, Hugo

As the name suggests, apoplastic effectors are localized to plant extracellular spaces. This class of effectors includes, but is not restricted to, small and cysteine-rich proteins which function primarily by inhibiting host proteases, hydrolases, glucanases, and other lytic enzymes. 13 Recent models suggest that these could be the first effectors to potentially activate the plant defense response (PTI). 13 The architecture of these effectors, often having a signal peptide and a cysteine-rich C-terminus, is highly reminiscent of plant small signaling peptides, 28 which may reflect the prototypic structure that a protein must harbor to survive its passage in apoplastic space. However, apoplastic effectors may have a much more refined mechanism and could exert a long-lasting action in protection of the pathogen cell wall or in chelating/neutralizing antimicrobial compounds being secreted by the host.