Plant NLR proteins recognize effectors (green) either directly or indirectly. (A) Indirect effector recognition occurs through monitoring effector-induced modifications of an intermediate guardee or decoy protein (black). (B) Direct effector recognition often occurs via interaction with the LRR domain (left) or with an ID (red), a decoy protein integrated with the NLR protein that mediates direct effector recognition. Such NLR-ID proteins often occur as part of a sensor/executor NLR pair, with both proteins required for specific resistance.