Category: Latest-Research-en

New paper from our laboratory

Kovi, B., Sakai, T., Abe, A., Kanzaki, E., Terauchi, R., & Shimizu, M. (2023). Isolation of Pikps, an allele of Pik, from the aus rice cultivar Shoni. Genes & Genetic Systems, advpub. https://doi.org/10.1266/ggs.22-00002

Abstract

Blast disease caused by the filamentous fungus Pyricularia oryzae (syn. Magnaporthe oryzae) is one of the most destructive diseases of rice (Oryza sativa L.) around the globe. An aus cultivar, Shoni, showed resistance against at least four Japanese P. oryzae isolates. To understand Shoni’s resistance against the P. oryzae isolate Naga69-150, genetic analysis was carried out using recombinant inbred lines developed by a cross between Shoni and the japonica cultivar Hitomebore, which is susceptible to Naga69-150. The result indicated that the resistance was controlled by a single locus, which was named Pi-Shoni. A QTL analysis identified Pi-Shoni as being located in the telomeric region of chromosome 11. A candidate gene approach in the region indicated that Pi-Shoni corresponds to the previously cloned Pik locus, and we named this allele Pikps. Loss of gene function mediated by RNA interference demonstrated that a head-to-head-orientated pair of NBS-LRR receptor genes (Pikps-1 and Pikps-2) are required for the Pikps-mediated resistance. Amino acid sequence comparison showed that Pikps-1 is 99% identical to Pikp-1, while Pikps-2 is identical to Pikp-2. Pikps-1 had one amino acid substitution (Pro351Ser) in the NBS domain as compared to Pikp-1. The recognition specificity of Pikps against known AVR-Pik alleles is identical to that of Pikp.

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.

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

Shimizu, M., Hirabuchi, A., Sugihara, Y., Abe, A., Takeda, T., Kobayashi, M., Hiraka, Y., Kanzaki, E., Oikawa, K., Saitoh, H., Thorsten, L., J, B. M., Kamoun, S. & Terauchi, R. (2022). A genetically linked pair of NLR immune receptors shows contrasting patterns of evolution. Proceedings of the National Academy of Sciences, 119(27), e2116896119. https://doi.org/10.1073/pnas.2116896119

Abstract

Throughout their evolution, plant nucleotide-binding leucine-rich-repeat receptors (NLRs) have acquired widely divergent unconventional integrated domains that enhance their ability to detect pathogen effectors. However, the functional dynamics that drive the evolution of NLRs with integrated domains (NLR-IDs) remain poorly understood. Here, we reconstructed the evolutionary history of an NLR locus prone to unconventional domain integration and experimentally tested hypotheses about the evolution of NLR-IDs. We show that the rice (Oryza sativa) NLR Pias recognizes the effector AVR-Pias of the blast fungal pathogen Magnaporthe oryzae. Pias consists of a functionally specialized NLR pair, the helper Pias-1 and the sensor Pias-2, that is allelic to the previously characterized Pia pair of NLRs: the helper RGA4 and the sensor RGA5. Remarkably, Pias-2 carries a C-terminal DUF761 domain at a similar position to the heavy metal–associated (HMA) domain of RGA5. Phylogenomic analysis showed that Pias-2/RGA5 sensor NLRs have undergone recurrent genomic recombination within the genus Oryza, resulting in up to six sequence-divergent domain integrations. Allelic NLRs with divergent functions have been maintained transspecies in different Oryza lineages to detect sequence-divergent pathogen effectors. By contrast, Pias-1 has retained its NLR helper activity throughout evolution and is capable of functioning together with the divergent sensor-NLR RGA5 to respond to AVR-Pia. These results suggest that opposite selective forces have driven the evolution of paired NLRs: highly dynamic domain integration events maintained by balancing selection for sensor NLRs, in sharp contrast to purifying selection and functional conservation of immune signaling for helper NLRs.

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

Natsume, S., Sugihara, Y., Kudoh, A., Oikawa, K., Shimizu, M., Ishikawa, Y., Nishihara, M., Abe, A., Innan, H., & Terauchi, R. (2022). Genome Analysis Revives a Forgotten Hybrid Crop Edo-dokoro in the Genus Dioscorea. Plant and Cell Physiology, pcac109. https://doi.org/10.1093/pcp/pcac109

Abstract

A rhizomatous Dioscorea crop “Edo-dokoro” was described in old records of Japan, but its botanical identify has not been characterized. We found that Edo-dokoro is still produced by four farmers in Tohoku-machi of Aomori Prefecture, Japan. Rhizomes of Edo-dokoro are a delicacy to the local people and are sold in the markets. Morphological characters of Edo-dokoro suggest its hybrid origin between the two species, D. tokoro and D. tenuipes. Genome analysis revealed that Edo-dokoro is likely originated by hybridization of a male D. tokoro to a female D. tenuipes, followed by a backcross with a male plant of D. tokoro. Edo-dokoro is a typical minor crop possibly maintained for more than 300 years but now almost forgotten from the public. We hypothesize that there are many such uncharacterized genetic heritages passed over generations by small scale farmers that await serious scientific investigation for future use and improvement by using modern genomics information.