Fungi secrete effector proteins, including extracellular redox enzymes, to inhibit host immunity. Redox enzymes have been hypothesized to inhibit host reactive oxygen species (ROS); however, how they suppress host immunity remains unknown. We characterized an extracellular ascorbate peroxidase (MoApx1) that is secreted into rice chloroplasts by the rice blast fungus Magnaporthe oryzae. MoApx1 displays multifunctional capabilities that significantly contribute to fungal virulence. Firstly, MoApx1 neutralizes host-derived H2O2 within the chloroplast through its peroxidase activity, thereby inhibiting chloroplast ROS (cROS)-mediated defense responses. Secondly, MoApx1 targets the photosystem I subunit OsPsaD, disrupting photosynthetic electron transport to further suppress cROS production. Most importantly, MoApx1 has evolved a fungal-specific starch-binding domain that binds host starch, inhibiting its degradation and disrupting the energy supply required for host resistance. Our findings underscore the importance of a novel multifaceted strategy, potentially widely employed by other fungal pathogens, in suppressing host immunity during host–microbe interactions.

Rice blast caused by Magnaporthe oryzae poses a major threat to world food supply. Conditions conducive to the disease include insufficient light. Our previous studies found that light-dependent phosphorylation of light-harvesting complex II protein (LHCB5) mediates rice immunity; however, the underlying mechanisms, in particular, the upstream regulators of LHCB5 phosphorylation, remain unknown. Here, we show that OsLIKE1 functions as a lectin receptor-like kinase (LecRLK) to play a critical role in rice resistance against M. oryzae. OsLIKE1 interacts with and phosphorylates LHCB5. In addition, we find two phosphorylation sites in the kinase domain of OsLIKE1 important for its auto-phosphorylation and phosphorylation of LHCB5. Moreover, we find that variation in light-induced OsLIKE1 expression is driven by specific single-nucleotide polymorphisms (SNPs) within the promoter region. These SNPs promote the auto-phosphorylation of OsLIKE1 to phosphorylate LHCB5 and activate its immune function against the blast fungus. Collectively, these findings elucidate the mechanism by which light regulates OsLIKE1-dependent defense in rice and support SNP-based rice breeding programs that increase disease resistance.

Rice blast, caused by Pyricularia oryzae, is one of the most destructive rice diseases worldwide. It is essential to understand the population structure and race distribution of P. oryzae for the prevention and control of rice blast. This study collected 1584 isolates across Jiangsu province from 2003 to 2017 to determine race diversity, common and dominant race structures, and resistance profiles using eight parameters from the Chinese differential cultivars (CDC) entries. Race diversity analysis indicated that the race diversity of 1584 isolates in Jiangsu province increased from 2003 to 2006 and fluctuated steadily from 2007 to 2017. Common race structure analysis showed that the common race structure of the isolates fluctuated wildly on an annual basis. Moreover, the race ZG1 was the dominant race, suggesting that the most commonly grown rice varieties in Jiangsu are highly adaptive to race ZG1. In addition, due to a higher level (>85%) of resistance to the population of isolates from 2003 to 2017, Tetep may be conformed as the most promising donor of blast resistance for resistance breeding in Jiangsu province. In summary, it is beneficial to control rice blast by continuous monitoring of the population structure and distribution of P. oryzae with the monogenic germplasm entries and by maintaining a diversity of rice varieties.

Phytophthora capsici is one of the devastating pathogens, causing foliar blight, root rot, and fruit rot in peppers. Cinnamaldehyde (CA) is a natural compound coming from Cinnamomum cassia. The medicinal properties of CA have been widely identified. Limited knowledge is known about the application of CA in agriculture. In this study, CA significantly inhibited P. capsici, which further suppressed Phytophthora blights in both pepper seedlings and pepper fruits. Treatment with CA resulted in collapsed and fragmented hyphae, accompanying the increase in MDA (malondialdehyde) content and the decrease in intercellular glycerol content in hyphae. CA also inhibited the growth of wild type yeast. The yeast mutant ΔYvc1 with a deletion of Yvc1 (a Ca²⁺ transporter) showed decreased sensitivity to CA. The transformation of PcNCX1, a sodium/calcium exchanger from P. capsici, into ΔYvc1 restored its sensitivity to CA. The transformant carrying PcNCX1 also showed restored Ca²⁺ efflux upon CA treatment. RNA-seq analysis showed that CA treatments resulted in the down-regulation of a set of genes encoding for calcium-related proteins. Collectively, our study demonstrates that the antifungal activity of CA against P. capsici may be associated with PcNCX1-mediated Ca²⁺ efflux. Our results provide crucial insights into the antimicrobial action of CA.

Rhizopus species are a leading cause of mucormycosis, an aggressive and life-threatening invasive fungal disease that affects immunocompromised individuals. Despite their clinical importance, mucoralean pathogens, especially R. delemar, are difficult to manipulate genetically because of coenocytic growth, multinucleate hyphae, difficulty with transformation, and limited selectable markers. These obstacles hinder the study of innate stress resistance and disease mechanisms. Previous efforts to express heterologous genes or implement gene-editing systems with vectors designed for model fungi have been largely unsuccessful or inefficient in R. delemar, suggesting unique requirements for gene expression in this organism. In this study, we tested nuclear-targeted fluorescent protein expression and identified differences in proline and arginine codon usage between heterologous and endogenous coding sequences. We then evaluated gene expression efficiency using various combinations of heterologous and endogenous regulatory elements and coding sequences, including six promoters, two terminators, three histone fusion proteins, and two fluorescent reporters, with or without an exogenous nuclear localization signal (NLS). Endogenous promoters orthologous to those with high transcriptional activity produced robust fluorescence, in contrast to weak fluorescence from constructs with heterologous sequences. Notably, fluorescence was also observed in a construct lacking an experimentally provided terminator, and the H2B-GFP fusion protein did not require an exogenous NLS for nuclear localization. These results show that efficient heterologous gene expression in R. delemar requires optimization at several levels, including promoter selection, coding sequence compatibility, and expression-cassette design. Although the direct impact of codon usage on expression efficiency remains to be tested, the expression systems developed here provide a platform for molecular analysis of R. delemar biology and pathogenesis.