Lysin Motif–Containing Proteins LYP4 and LYP6 Play Dual Roles in Peptidoglycan and Chitin Perception in Rice Innate Immunity

Abstract

Plant innate immunity relies on successful detection of microbe-associated molecular patterns (MAMPs) of invading microbes via pattern recognition receptors (PRRs) at the plant cell surface. Here, we report two homologous rice (Oryza sativa) lysin motif-containing proteins, LYP4 and LYP6, as dual functional PRRs sensing bacterial peptidoglycan (PGN) and fungal chitin. Live cell imaging and microsomal fractionation consistently revealed the plasma membrane localization of these proteins in rice cells. Transcription of these two genes could be induced rapidly upon exposure to bacterial pathogens or diverse MAMPs. Both proteins selectively bound PGN and chitin but not lipopolysaccharide (LPS) in vitro. Accordingly, silencing of either LYP specifically impaired PGN-or chitin-but not LPS-induced defense responses in rice, including reactive oxygen species generation, defense gene activation, and callose deposition, leading to compromised resistance against bacterial pathogen Xanthomonas oryzae and fungal pathogen Magnaporthe oryzae. Interestingly, pretreatment with excess PGN dramatically attenuated the alkalinization response of rice cells to chitin but not to flagellin; vice versa, pretreatment with chitin attenuated the response to PGN, suggesting that PGN and chitin engage overlapping perception components in rice. Collectively, our data support the notion that LYP4 and LYP6 are promiscuous PRRs for PGN and chitin in rice innate immunity.

LYM2-dependent chitin perception limits molecular flux via plasmodesmata

“…Given the plethora of small, defense-associated molecules involved in plant defense, it must be determined which of these have a role in intercellular signaling. With respect to the different mechanisms of chitin perception between rice and Arabidopsis, it remains to investigate chitin-triggered PD closure in rice and whether this is mediated by the CEBiP/OsCERK1 complex or by another member of the lysin motif-containing protein family (27). The purpose served by a reduction in cellto-cell communication during defense responses remains to be explained, but through its identification and its protein mediator, we can now actively pursue deeper questions relating to PD function during plant-pathogen interactions.…”

OsLYP4 and OsLYP6 play critical roles in rice defense signal transduction

“…These results are consistent with our former data, in which knockdown of either OsLYP genes could increase rice susceptibility to both fungal and bacterial pathogens. 10 Considering that these microbial pathogens contain a cocktail of MAMPs, 11 these data suggested that PGN or chitin signaling mediated by OsLYP4 and OsLYP6 contributes significantly to rice defense responses against bacteria and fungi.…”

“…10 Moreover, another lysin motif-containing protein, CEBiP has been reported to play important role in chitin sensing and signal transduction. 12,13 Therefore, we investigated the protein-protein interactions between these LYP proteins with yeast two-hybrid (Y2H).…”

“…9 Recently, we identified two rice LysM proteins, OsLYP4 and OsLYP6, play dual function in chitin and PGN perception. 10 In this research, to investigate the influence of OsLYP4 and OsLYP6 in pathogen-induced defense-related gene activation in rice, we tested the selected marker genes, such as Beta-Glu (Os05 g0495900) and PAL (Os02 g0627100) in OsLYP4 and OsLYP6 RNAi rice. The induction of the selected marker genes was monitored by qPCR at different time points after the fungal blast pathogen Magnaporthe Plant innate immunity relies on successful detection of trespassing pathogens through recognizing their microbeassociated molecular patterns (mamPs) by pattern recognition receptors (PRRs) at the cell surface.…”

BIK1 interacts with PEPRs to mediate ethylene-induced immunity

“…Plant cell surface-localized immune receptors, also called pattern-recognition receptors (PRRs), consist of a variety of receptor-like kinases and receptor-like proteins. Many PRRs, including FLS2, EFR, Xa21, CERK1, CEBiP, LYM1, LYM3, LYP4, and LYP6 (1)(2)(3)(4)(5)(6)(7)(8), directly sense pathogen/microbe-associated molecular patterns (PAMPs), such as flagellin, elongation factor, quorum-sensing protein, or peptidoglycans from bacteria or chitin from fungal cell wall. In addition to PAMPs, PRRs also perceive endogenous damage-associated molecular patterns (DAMPs), such as plant cell wall fragments released by pathogen lytic enzymes or plant peptides synthesized de novo during pathogen infection.…”