CHAPTER 8: Chitin receptor for plant innate immunity

Two types of LysM receptors, CEBiP and CERK1, play critical roles for chitin recognition and defense signaling in rice and Arabidopsis. In rice, both CEBiP and OsCERK1 are required for oligochitin-induced defense responses. However, we are still not able to detect the CEBiP-like molecule in Arabidopsis membrane preparations, indicating that the amount of this molecule is much less compared to rice, or that the efficiency of affinity cross-linking with the present ligand is not equal for rice and Arabidopsis. This result also suggests that the machinery for chitin elicitor signaling may differ between monocot (rice) and dicot (Arabidopsis) plants. Other LysM receptor kinases, NFR1 and NFR5 in L. japonicas and LYK3 in M. truncatula, play a major role in the perception of Nod factors, which are derivatives of oligochitin and essential for nodulation signaling. It is interesting that the initiator of opposite biological responses, defense and symbiotic reactions, share a common structure. However, the question still remains as to how these receptors distinguishably regulate their downstream signaling pathway. Further studies are necessary to answer these intriguing questions.