Author: OHTAAtsushi

This paper has been published in which Prof. Terauchi is the corresponding author.

Takeda, T., Takahashi, M., Shimizu, M., Sugihara, Y., Yamashita, T., Saitoh, H., Fujisaki, K., Ishikawa, K., Utsushi, H., Kanzaki, E., Sakamoto, Y., Abe, A., & Terauchi, R. (2022). Rice apoplastic CBM1-interacting protein counters blast pathogen invasion by binding conserved carbohydrate binding module 1 motif of fungal proteins. PLOS Pathogens, 18(9), e1010792-. https://doi.org/10.1371/journal.ppat.1010792

Abstract

When infecting plants, fungal pathogens secrete cell wall-degrading enzymes (CWDEs) that break down cellulose and hemicellulose, the primary components of plant cell walls. Some fungal CWDEs contain a unique domain, named the carbohydrate binding module (CBM), that facilitates their access to polysaccharides. However, little is known about how plants counteract pathogen degradation of their cell walls. Here, we show that the rice cysteine-rich repeat secretion protein OsRMC binds to and inhibits xylanase MoCel10A of the blast fungus pathogen Magnaporthe oryzae, interfering with its access to the rice cell wall and degradation of rice xylan. We found binding of OsRMC to various CBM1-containing enzymes, suggesting that it has a general role in inhibiting the action of CBM1. OsRMC is localized to the apoplast, and its expression is strongly induced in leaves infected with M. oryzae. Remarkably, knockdown and overexpression of OsRMC reduced and enhanced rice defense against M. oryzae, respectively, demonstrating that inhibition of CBM1-containing fungal enzymes by OsRMC is crucial for rice defense. We also identified additional CBM-interacting proteins (CBMIPs) from Arabidopsis thaliana and Setaria italica, indicating that a wide range of plants counteract pathogens through this mechanism.

Author summary

Plants have evolved various activity-inhibiting proteins as a defense against fungal cell wall-degrading enzymes (CWDEs), but how plants counteract the function of fungal enzymes containing carbohydrate binding modules (CBMs) remains unknown. Here, we demonstrate that OsRMC, a member of the cysteine-rich repeat secretion protein family, interacts with fungal CBM1. OsRMC binding to CBM1 of a blast fungal xylanase blocks access to cellulose, resulting in the inhibition of xylanase enzymatic activity. Our study provides significant insights into plant countermeasures against CWDEs in the apoplastic space during plant-fungal pathogen interactions. It also reveals a molecular function of the DUF26 domain widely distributed in plant proteins.

REVIEW ARTICLE

Kourelis, J., & Adachi, H. (2022). Activation and Regulation of NLR Immune Receptor Networks. Plant and Cell Physiology, pcac116. https://doi.org/10.1093/pcp/pcac116

Abstract

Plants have many types of immune receptors that recognize diverse pathogen molecules and activate the innate immune system. The intracellular immune receptor family of nucleotide-binding domain leucine-rich repeat–containing proteins (NLRs) perceive translocated pathogen effector proteins and execute a robust immune response, including programmed cell death. Many plant NLRs have functionally specialized to sense pathogen effectors (sensor NLRs) or to execute immune signalling (helper NLRs). Sub-functionalized NLRs form a network-type receptor system known as the NLR network. In this review, we highlight the concept of NLR networks, discussing how they are formed, activated, and regulated. Two main types of NLR networks have been described in plants: the ADR1/NRG1 network and the NRC network. In both networks, multiple helper NLRs function as signalling hubs for sensor NLRs and cell surface–localized immune receptors. Additionally, the networks are regulated at the transcriptional and posttranscriptional levels, as well as being modulated by other host proteins to ensure proper network activation and prevent autoimmunity. Plant pathogens in turn have converged on suppressing NLR networks, thereby facilitating infection and disease. Understanding the NLR immune system at the network level could inform future breeding programs by highlighting the appropriate genetic combinations of immunoreceptors to use while avoiding deleterious autoimmunity and suppression by pathogens.