Effector MoSDT1 enhances Magnaporthe oryzae virulence and plays a dual role in regulating rice defense.

C2H2 zinc effectors are a class of pathogen proteins that play a dual role in plant-pathogen interactions, promoting pathogenicity and enhancing plant defense. In our previous research, we identified Magnaporthe oryzae Systemic Defense Trigger 1 (MoSDT1) as a C2H2 zinc effector that activates rice (Oryza sativa) defense when overexpressed in rice. However, its regulatory roles in pathogenicity and defense require further investigation. In this study, we generated an MoSDT1 overexpressing strain and 2 knockout strains of M. oryzae to assess the impact of MoSDT1 on pathogenicity, rice defense, and phenotypic characteristics. Our analyses revealed that MoSDT1 substantially influenced vegetative growth, conidia size, and conidiation, and was crucial for the virulence of M. oryzae while suppressing rice defense. MoSDT1 localized to the nucleus and cytoplasm of rice, either dependent or independent of M. oryzae delivery. Through RNA-seq, scRNA-seq, and ChIP-seq, we identified that MoSDT1 modulates rice defense by regulating the phosphorylation and ubiquitination of various rice signaling proteins, including transcription factors, transcription repressors, kinases, phosphatases, and the ubiquitin system. These findings provide valuable insights into the regulatory mechanisms of C2H2 zinc finger effector proteins and offer important foundational information for utilizing their target genes in disease resistance breeding and the design of targets for disease management.

Characterization of infected process and primary mechanism in rice Acuce defense against rice blast fungus, Magnaporthe oryzae.

KEY MESSAGE: Identification of infection process and defense response during M. oryzae infecting Acuce. Magnaporthe oryzae is a destructive rice pathogen. Recent studies have focused on the initial infectious stage, with a few studies conducted to elucidate the characteristics of the late infectious stages. This study aims to decipher the characteristics at different stages (biotrophic, biotrophy-necrotrophy switch (BNS), and necrotrophic) between the interaction of two M. oryzae-rice combinations and investigate the resistance mechanisms of rice to M. oryzae using cytological and molecular methods. The biotrophic phase of M. oryzae-LTH compatible interaction was found to be longer than that of M. oryzae-Acuce incompatible interaction. We also found that jasmonic acid (JA) signaling plays an important role in defense by regulating antimicrobial compound accumulation in infected Acuce via a synergistic interaction of JA-salicylic acid (SA) and JA-ethylene (ET). In infected LTH, JA-ET/JA-SA showed antagonistic interaction. Ibuprofen (IBU) is a JA inhibitor. Despite the above findings, we found that exogenous JA-Ile and IBU significantly alleviated blast symptoms in infected LTH at 36 hpi (biotrophic) and 72 hpi (BNS), indicating these two-time points may be critical for managing blast disease in the compatible interaction. Conversely, IBU significantly increased blast symptoms on the infected Acuce at 36 hpi, confirming that the JA signal plays a central role in the defense response in infected Acuce. According to transcriptional analysis, the number of genes enriched in the plant hormone signal pathway was significantly higher than in other pathways. Our findings suggested that JA-mediated defense mechanism is essential in regulating Acuce resistance, particularly during the biotrophic and BNS phases.

Multi-Omics Approach Reveals OsPIL1 as a Regulator Promotes Rice Growth, Grain Development, and Blast Resistance.

Rice (Oryza sativa) is a crucial crop, achieving high yield concurrent pathogen resistance remains a challenge. Transcription factors play roles in growth and abiotic tolerance. However, rice phytochrome-interacting factor-like 1 (OsPIL1) in pathogen resistance and agronomic traits remains unexplored. We generated OsPIL1 overexpressing (OsPIL1 OE) rice lines and evaluated their impact on growth, grain development, and resistance to Magnaporthe oryzae. Multiomics analysis (RNA-seq, metabolomics, and CUT&Tag) and RT-qPCR validated OsPIL1 target genes and key metabolites. In the results, OsPIL1 OE rice lines exhibited robust growth, longer grains, and enhanced resistance to M. oryzae without compromising growth. Integrative multiomics analysis revealed a coordinated regulatory network centered on OsPIL1, explaining these desirable traits. OsPIL1 likely acts as a positive regulator, targeting transcriptional elements or specific genes with direct functions in several biological programs. In particular, a range of key signaling genes (phosphatases, kinases, plant hormone genes, transcription factors), and metabolites (linolenic acid, vitamin E, trigonelline, d-glucose, serotonin, choline, genistein, riboflavin) contributed to enhanced rice growth, grain size, pathogen resistance, or a combination of these traits. These findings highlight OsPIL1's regulatory role in promoting important traits and provide insights into potential strategies for rice breeding.

Exogenous Jasmonic Acid Alleviates Blast Resistance Reduction Caused by LOX3 Knockout in Rice.

Lipoxygenase 3 (LOX3) is a lipid peroxidase found in rice embryos that is known to affect seed quality. Interestingly, deletion of the LOX3 gene has been shown to improve rice seed quality but decrease resistance to rice blast disease and drought. To investigate these opposing effects, we generated a LOX3 knockout construct (ΔLox3) in rice (Oryza sativa L.) plants. Blast resistance and transcription levels of rice genes in ΔLox3 rice plants and the effects of exogenous jasmonic acid (JA) on resistance and transcriptional levels of rice genes in Magnaporthe oryzae-infected ΔLox3 rice plants were further elucidated. The results showed that the ΔLox3 plants exhibited normal phenotypes, with high levels of methyl-linolenate and reactive oxygen species (ROS), and the genes involved in three Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways contributed to rice seed quality. M. oryzae-infected ΔLox3 plants exhibited serious blast symptoms with a reduced defense response but increased ROS-mediated cell death, and the genes involved in seven KEGG pathways contributed to rice seed quality. Exogenous JA treatment alleviated blast symptoms in infected ΔLox3 plants by hindering hyphal expansion, inhibiting ROS-mediated cell death, and increasing the defense response, and genes involved in 12 KEGG pathways contributed to rice seed quality. These findings demonstrate that LOX3 plays an important role in rice growth and defense, and its knockout improves rice quality at the expense of disease resistance. Exogenous JA provides a means to compensate for the reduction in defense responses of LOX3 knockout rice lines, suggesting potential applications in agricultural production.