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REVIEW ARTICLE

Adachi, H., & Kamoun, S. (2022). NLR receptor networks in plants. Essays in Biochemistry, EBC20210075. https://doi.org/10.1042/EBC20210075

Abstract

To fight off diverse pathogens and pests, the plant immune system must recognize these invaders; however, as plant immune receptors evolve to recognize a pathogen, the pathogen often evolves to escape this recognition. Plant–pathogen co-evolution has led to the vast expansion of a family of intracellular immune receptors-nucleotide-binding domain and leucine-rich repeat proteins (NLRs). When an NLR receptor recognizes a pathogen ligand, it activates immune signaling and thus initiates defense responses. However, in contrast with the model of NLRs acting individually to activate resistance, an emerging paradigm holds that plants have complex receptor networks where the large repertoire of functionally specialized NLRs function together to act against the large repertoire of rapidly evolving pathogen effectors. In this article, we highlight key aspects of immune receptor networks in plant NLR biology and discuss NLR network architecture, the advantages of this receptor network system, and the evolution of the NLR network in asterid plants.

加藤大明研究員らの論文がサイエンスに掲載されました。

Kato, H., Nemoto, K., Shimizu, M., Abe, A., Asai, S., Ishihama, N., Matsuoka, S., Daimon, T., Ojika, M., Kawakita, K., Onai, K., Shirasu, K., Yoshida, M., Ishiura, M., Takemoto, D., Takano, Y., & Terauchi, R. (2022). Recognition of pathogen-derived sphingolipids in Arabidopsis. Science, 376(6595), 857–860. https://doi.org/10.1126/science.abn0650

Abstruct

In plants, many invading microbial pathogens are recognized by cell-surface pattern recognition receptors, which induce defense responses. Here, we show that the ceramide Phytophthora infestans–ceramide D (Pi-Cer D) from the plant pathogenic oomycete P. infestans triggers defense responses in Arabidopsis. Pi-Cer D is cleaved by an Arabidopsis apoplastic ceramidase, NEUTRAL CERAMIDASE 2 (NCER2), and the resulting 9-methyl–branched sphingoid base is recognized by a plasma membrane lectin receptor–like kinase, RESISTANT TO DFPM-INHIBITION OF ABSCISIC ACID SIGNALING 2 (RDA2). 9-Methyl–branched sphingoid base is specific to microbes and induces plant immune responses by physically interacting with RDA2. Loss of RDA2 or NCER2 function compromised Arabidopsis resistance against an oomycete pathogen. Thus, we elucidated the recognition mechanisms of pathogen-derived lipid molecules in plants.

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

Kobayashi, M., Utsushi, H., Fujisaki, K., Takeda, T., Yamashita, T., & Terauchi, R. (2022). A jacalin-like lectin domain-containing protein of Sclerospora graminicola acts as an apoplastic virulence effector in plant–oomycete interactions. Molecular Plant Pathology, 23, 845– 854. https://doi.org/https://doi.org/10.1111/mpp.13197

Abstruct

The plant extracellular space, including the apoplast and plasma membrane, is the initial site of plant–pathogen interactions. Pathogens deliver numerous secreted proteins, called effectors, into this region to suppress plant immunity and establish infection. Downy mildew caused by the oomycete pathogen Sclerospora graminicola (Sg) is an economically important disease of Poaceae crops including foxtail millet (Setaria italica). We previously reported the genome sequence of Sg and showed that the jacalin-related lectin (JRL) gene family has significantly expanded in this lineage. However, the biological functions of JRL proteins remained unknown. Here, we show that JRL from Sg (SgJRL) functions as an apoplastic virulence effector. We identified eight SgJRLs by protein mass spectrometry analysis of extracellular fluid from Sg-inoculated foxtail millet leaves. SgJRLs consist of a jacalin-like lectin domain and an N-terminal putative secretion signal; SgJRL expression is induced by Sg infection. Heterologous expression of three SgJRLs with N-terminal secretion signal peptides in Nicotiana benthamiana enhanced the virulence of the pathogen Phytophthora palmivora inoculated onto the same leaves. Of the three SgJRLs, SG06536 fused with green fluorescent protein (GFP) localized to the apoplastic space in N. benthamiana leaves. INF1-mediated induction of defence-related genes was suppressed by co-expression of SG06536-GFP. These findings suggest that JRLs are novel apoplastic effectors that contribute to pathogenicity by suppressing plant defence responses.