MoNeo1 belongs to a family of enzymes known as P4-ATPases, or phospholipid flippases. These molecular pumps perform a deceptively simple but profoundly important task: they grab specific phospholipids from the outer, luminal leaflet of a cellular membrane and flip them to the inner, cytosolic leaflet. In doing so, they create what biologists call lipid asymmetry — a deliberate imbalance in the distribution of phospholipids between the two faces of a membrane. That asymmetry is not a cosmetic detail. It changes the physical properties of the membrane, curvature, charge, and fluidity, and it is a prerequisite for the budding of transport vesicles from the trans-Golgi network and endosomal membranes. In budding yeast, the Neo1 protein is essential for life; in humans, mutations in the Neo1 ortholog ATP9A are linked to hypotonia, intellectual disability, and attention deficit hyperactivity disorder. Until now, however, the role of this conserved flippase in plant-pathogenic fungi had not been systematically explored.

The team began by searching the M. oryzae genome for a counterpart of the well-characterized yeast Neo1. A BLAST search against the Kyoto Encyclopedia of Genes and Genomes returned a single strong candidate, the product of gene MGG_04066, which shares 55.28 percent amino acid identity with its yeast ortholog across eighty percent of the protein length. Phylogenetic analysis confirmed that Neo1 is tightly conserved across filamentous fungi, clustering closely with homologs from Botrytis cinerea and Aspergillus oryzae. Structural predictions generated with AlphaFold2, refined against known homologous structures, revealed the canonical P4-ATPase architecture: a transmembrane domain embedded in the lipid bilayer, flanked by the actuator, nucleotide-binding, and phosphorylation domains that together drive the ATP-powered flipping cycle. In short, MoNeo1 looked every bit the genuine flippase, and the researchers were ready to ask what happens when it is removed.

The answer, obtained through targeted gene deletion by homologous recombination, was dramatic. The ΔMoneo1 mutant remained viable — unlike its yeast counterpart — but its growth was visibly stunted across four different culture media compared with the wild-type Guy11 strain and a genetically complemented control. More striking still was the effect on asexual reproduction. Conidia, the spores through which rice blast spreads from plant to plant, were reduced by approximately 87.3 percent in the mutant, and the conidiophores that produce them developed abnormally. Because conidiation is the engine of disease persistence and dissemination in the field, this single defect would be enough to cripple an epidemic. Yet the most consequential phenotype emerged when the researchers turned their attention to infection itself.

M. oryzae initiates infection by germinating a conidium on the leaf surface and building a specialized dome-shaped structure called an appressorium, which generates enormous internal turgor pressure to mechanically breach the rice cuticle. In the ΔMoneo1 mutant, germ tubes elongated abnormally and appressorium formation was delayed, falling by more than fifty percent relative to the wild type at early time points, although the structures eventually formed by twenty-four hours. Formation, however, was not the same as function. Cytorrhysis assays, in which appressoria are challenged with increasing concentrations of glycerol to measure their internal pressure, revealed that mutant appressoria collapsed at significantly higher rates, indicating reduced turgor. Nile red staining showed impaired lipid retention at six and sixteen hours after induction, suggesting a failure in the glycerol generation that fuels the pressure build-up. Consistent with these functional deficits, the mutant produced far fewer invasive hyphae inside rice leaf sheaths, and blast symptoms on both barley leaves and susceptible CO39 rice seedlings were greatly reduced.

The mechanistic thread running through these phenotypes appears to be lipid chemistry. Quantitative lipidomics by high-performance liquid chromatography coupled to mass spectrometry revealed that deletion of MoNEO1 threw the fungus’s phospholipid economy into disarray. Levels of phosphatidylcholine rose by forty-two percent, phosphatidylethanolamine by thirty-eight percent, phosphatidylserine by twenty-one percent, and phosphatidylinositol by nineteen percent, while phosphatidic acid fell by twenty-eight percent and lysophosphatidylethanolamine by seventeen percent. Storage and signaling lipids shifted as well, with triacylglycerol increasing by twenty-three percent and diacylglycerol by fourteen percent. Nearly all of these changes were reversed in the complemented strain, confirming that they were specifically attributable to the loss of MoNeo1. The mutant was also hypersensitive to membrane stress induced by sodium chloride and Calcofluor White, consistent with a compromised membrane barrier. Together, the data paint MoNeo1 as a guardian of phospholipid homeostasis whose absence forces the cell into a compensatory rerouting of lipid metabolism.

Where does MoNeo1 do its work? Live-cell fluorescence microscopy of a MoNeo1-GFP fusion expressed under its native promoter showed the protein as discrete, motile puncta throughout the fungal life cycle. Co-expression with the trans-Golgi network marker MoKex2-mCherry revealed partial co-localization, and labeling of early endosomes with the dye FM4-64 showed transient overlap as well. MoNeo1, in other words, resides at the interface between the trans-Golgi network and the endosomal system — precisely the crossroads through which retrograde cargo traffic must pass. The team then asked how this steady-state distribution is maintained, focusing on the retromer, a conserved pentameric complex that retrieves membrane proteins from endosomes and returns them to the trans-Golgi network, thereby rescuing them from degradation in the vacuole. In yeast, Neo1 is a known retromer cargo, and the researchers suspected the same relationship might hold in M. oryzae.

It did. Co-immunoprecipitation experiments recovered MoNeo1-Flag together with MoVps35-GFP, the cargo-recognition core of the retromer, and live-cell imaging showed the two proteins traveling together on motile puncta through the hyphal cytoplasm. The dependency ran in one direction only: when MoVPS35 was deleted, MoNeo1-GFP vanished from its normal trans-Golgi and endosomal puncta and accumulated instead on the vacuolar membrane, in both vegetative hyphae and conidia. Deleting MoNEO1, by contrast, left the distribution of MoVps35 untouched. The retromer, therefore, sits upstream, continuously recycling MoNeo1 back to its functional address and protecting it from vacuolar degradation. This is a textbook retrograde trafficking relationship, now demonstrated for the first time in a major plant pathogen.

The final piece of the puzzle connects lipid flipping to the secretion of virulence proteins. Affinity purification and mass spectrometry of MoNeo1-Flag complexes identified 521 candidate interacting proteins, among them MoSnc1, an R-SNARE protein known to mediate effector secretion and to travel on the endosome-to-plasma-membrane route. Co-immunoprecipitation confirmed a physical interaction between MoNeo1 and MoSnc1, and the two proteins partially co-localized in living cells. Crucially, in the ΔMoneo1 mutant, the number and size of MoSnc1-positive puncta shrank, and the SNARE was progressively mis-sorted into the vacuole for degradation, while MoNeo1 localization remained normal in a ΔMosnc1 background. The consequence for virulence was direct: the apoplastic effector Bas4 accumulated abnormally in the cytosol and vacuole, and the cytoplasmic effector Pwl2 formed misplaced cytosolic foci instead of being delivered into host cells. The researchers propose that the membrane asymmetry generated by MoNeo1 creates lipid environments — rich in appropriately distributed phosphatidylserine and phosphatidylethanolamine — that are required for the stability, fusion competence, and recycling of MoSnc1-containing transport intermediates. Without that lipid scaffolding, the entire secretion pipeline that arms the fungus for invasion collapses. The study thus reframes MoNeo1 not as a housekeeping enzyme but as a strategic coordinator, integrating retrograde protein sorting with lipid translocation to support appressorium function and host penetration. Because flippases of this family are conserved across fungal pathogens, including the wheat scab fungus Fusarium graminearum and the human pathogen Cryptococcus neoformans, the pathway defined here offers a template for targeted disease control strategies that could protect rice yields without relying on conventional fungicides.

Subject of Research: Role of the P4-ATPase lipid flippase MoNeo1 in vesicle trafficking and pathogenicity of the rice blast fungus Magnaporthe oryzae

Article Title: The lipid flippase MoNeo1 mediates vesicle trafficking and pathogenicity in Magnaporthe oryzae

Article References: Cai, Y., Huang, X., Nie, Y., Luan, Y., Aarti, A., Gong, Q., Sun, P., Abubakar, Y. S., Wang, B., Wang, A., Li, G., Lin, L., & Zheng, W. (2026). The lipid flippase MoNeo1 mediates vesicle trafficking and pathogenicity in Magnaporthe oryzae. Stress Biology, 6(1), Article 28. https://doi.org/10.1007/s44154-026-00305-5

Image Credits: AI Generated

DOI: 10.1007/s44154-026-00305-5

Keywords: Magnaporthe oryzae, rice blast, lipid flippase, P4-ATPase, MoNeo1, vesicle trafficking, retromer, MoVps35, MoSnc1, SNARE, effector secretion, appressorium

Most efforts to find genes that protect plants from pathogens rely on loss-of-function screens: researchers disable genes one by one and look for plants that become unusually susceptible. But this approach misses a large and valuable class of genes, those whose enhanced activity confers protection. Gain-of-function screens, in which genes are switched on rather than off, are far better at revealing positive regulators of resistance, and they directly nominate candidates that breeders might overexpress to harden crops. In mammalian cells, CRISPR-based activation screens have become routine, but their adoption in plants has lagged, largely because delivering large guide RNA libraries into intact plant tissues is difficult and because screening whole plants at genomic scale is slow and expensive.

The Chinese team sidestepped this bottleneck by working with rice protoplasts, single plant cells stripped of their cell walls, which can be transfected efficiently and en masse. The researchers built a guide RNA library targeting genes encoding receptor kinases and receptor-like cytoplasmic kinases, a large protein family in rice that spans hundreds of members and includes many known immune regulators. To turn target genes on, they deployed a catalytically dead Cas9 fused to transcriptional activation domains, the dCas9-TV system that Li’s laboratory previously developed for plants. When a guide RNA steers the dCas9-TV activator to a gene’s promoter, that gene’s expression is cranked up without altering the DNA sequence itself.

A clever reporter made the screen readable. The team used the promoter of OsChit6, a chitinase gene that is strongly induced during fungal infection, to drive a reporter construct, so that any guide RNA whose target gene activates this defense program would light up the cell. They adapted the INTACT method, which uses affinity-tagged nuclei, to isolate and enrich protoplasts in which the OsChit6 promoter had been activated. Deep sequencing of guide RNAs recovered from the enriched population then revealed which genes, when overexpressed, switched on the defense marker. The screen converged on a handful of candidates, including several receptor-like cytoplasmic kinases and, most strikingly, OsTV1, a gene with no previously assigned immune function.

Validation followed rapidly through conventional genetics. The researchers generated rice lines in which OsTV1 was overexpressed and independent lines in which it was knocked out using CRISPR/Cas9. The results were unambiguous: overexpression lines activated the OsChit6 defense marker more strongly, while knockout lines failed to mount normal basal and pathogen-induced OsChit6 expression when challenged with Magnaporthe oryzae, the ascomycete fungus responsible for rice blast, the most devastating rice disease worldwide. Protein domain analysis showed that OsTV1 encodes a receptor kinase carrying leucine-rich repeats, a single transmembrane segment and a serine/threonine kinase catalytic domain, an architecture typical of cell-surface signaling receptors. The authors also noted that a segment of the gene was mis-annotated in the standard rice genome annotation database, underscoring how easily such genes can be overlooked.

Confocal microscopy of OsTV1 fused to GFP revealed something unusual about where the protein resides. OsTV1 accumulates specifically at papillae, ring-like cell wall thickenings that epidermal cells build at their periphery as defensive barriers against invading fungi. Papillae are among the earliest and most important physical defenses a plant cell deploys, acting as fortified plugs that block fungal penetration pegs from breaching the cell wall. Remarkably, the papillae-specific localization of OsTV1 held both during normal plant development and following M. oryzae infection, and the fungus did not change the protein’s accumulation or distribution, suggesting OsTV1 functions as a constitutively deployed guardian of these structures rather than a stress-recruited one.

The mechanistic story that emerged centers on silicon, a nutrient that rice is famous for accumulating in prodigious quantities. OsTV1 overexpression increased silicon deposition in leaves and raised leaf rigidity, which the team quantified using nanoindentation assays that measure the mechanical stiffness of leaf tissue. Overexpression lines also showed elevated expression of lignin biosynthesis genes, reinforcing the biochemical armature of the cell wall. Conversely, OsTV1 knockout lines displayed moderately reduced leaf stiffness and weakened lignin gene expression. These findings tie a specific signaling receptor, for the first time, to the physical properties of the leaf that determine how easily a fungal penetration peg can force its way through. Notably, OsTV1 did not alter canonical chitin-triggered immune signaling: MAP kinase activation and reactive oxygen bursts after chitin treatment were unaffected, and co-immunoprecipitation showed no complex formation between OsTV1 and OsCERK1, the central chitin receptor co-receptor. OsTV1 therefore appears to operate on a parallel, physical-defense axis rather than as part of the classical immune signaling machinery.

The agricultural payoff is broad-spectrum. In greenhouse and laboratory assays, OsTV1 overexpression lines resisted M. oryzae more effectively, while knockout lines were markedly more susceptible. The protection extended beyond blast: overexpression lines also tolerated infection by Fusarium fujikuroi, the bakanae pathogen that causes seedling elongation disease, and by Rhizoctonia solani, the sheath blight pathogen that devastates stems and grains under field conditions. Field trials delivered perhaps the most compelling evidence. Under natural disease pressure, OsTV1 overexpression lines restricted neck blast lesions to the mid-panicle region while lesions spread nearly to the panicle base in control plants, and knockout lines suffered severe panicle withering. Against sheath blight, overexpression plants kept green stems and filled their grains normally, whereas knockouts developed extensive stem lesions and shriveled grain. Crucially, all of this protection came at no detectable cost to yield: grain length, grain width and hundred-grain weight were indistinguishable across the genotypes, addressing the long-standing concern that boosting physical defenses, particularly silicon deposition, might stunt growth or reduce harvest.

For molecular breeders, OsTV1 offers an attractive target precisely because it enhances a defense strategy that is intrinsic to rice physiology. Silicon fertilization is already practiced widely in rice agriculture, but its benefits depend on the plant’s capacity to deposit and mobilize the element at the right cellular locations. A receptor kinase that promotes silicon-mediated fortification could be edited, overexpressed or introgressed into elite cultivars to strengthen that capacity from within, potentially reducing fungicide dependence. Just as importantly, the screening platform itself is a significant contribution. Because it operates in protoplasts, it can compress a genome-scale functional search into a rapid cell-based assay, and because it uses dCas9-mediated activation rather than DNA editing, it leaves no permanent scars and can target any promoter sequence. The authors suggest the approach can be adapted to other genes and other cellular processes, from nutrient transport to stress tolerance, and with appropriate reporters and cell types, to other plant species as well. As fungal pathogens continue to evolve resistance to chemical controls and as climate change reshapes disease pressure on staple crops, tools that accelerate the discovery of native resistance mechanisms, and genes like OsTV1 that harness them without penalizing yield, are likely to attract intense attention from both plant scientists and breeders.

Subject of Research: A CRISPR activation screen identifying the papillae-specific receptor kinase OsTV1 as a positive regulator of silicon-mediated, broad-spectrum fungal resistance in rice

Article Title: Cell-based CRISPRa screen identifies a papillae-specific receptor kinase mediating broad-spectrum fungal resistance in rice

Article References: Wang, F.-Z., Bao, Y., Qiu, J., Chen, M.-X., Jiang, H., Li, Z., Xiong, X., Jiang, X., Kou, Y., & Li, J.-F. (2026). Cell-based CRISPRa screen identifies a papillae-specific receptor kinase mediating broad-spectrum fungal resistance in rice. Nature Plants. https://doi.org/10.1038/s41477-026-02385-7

Image Credits: AI Generated

DOI: 10.1038/s41477-026-02385-7

Keywords: rice, CRISPR activation screen, OsTV1, receptor kinase, fungal resistance, rice blast, Magnaporthe oryzae, silicon deposition, papillae, cell wall, lignin, plant immunity

Rice blast, caused by the fungus Magnaporthe oryzae, is widely regarded as the most devastating disease of rice worldwide. The pathogen attacks leaves, stems, and critically the grain-bearing panicles, and under favorable conditions it can wipe out a substantial share of a harvest. Farmers have long relied on fungicides and resistant cultivars, but the fungus is notorious for its ability to mutate and overcome single-gene defenses. That makes the search for broad-spectrum and stacked resistance genes a central priority for rice breeders everywhere, and it is precisely what makes the new findings so significant.

The research team, led by Thokchom Nepolian Singh and colleagues at the College of Agriculture, Central Agricultural University, Imphal, set out to determine which of the well-characterized blast resistance genes are already present in the region’s germplasm. Fifty-eight genotypes collected from across Northeastern India were evaluated, alongside a susceptible control genotype known as HR-12 and a resistant check variety called Tetep, a famous donor of blast resistance originally from Vietnam. The team grew all entries in a uniform blast nursery, an experimental setting designed to apply intense, natural disease pressure so that the true resistance reactions of each genotype could be observed and scored.

In parallel with the field evaluation, the researchers employed fourteen gene-specific molecular markers to detect the presence of known resistance genes in each genotype’s DNA. This marker-assisted screening approach exploits the fact that most major resistance genes can be tracked through tightly linked DNA sequences, allowing breeders to identify valuable genes without waiting years for field validation. The molecular analysis revealed a strikingly high frequency of resistance genes across the collection, confirming that Northeastern Indian rice landraces represent a largely untapped reservoir of blast resistance.

Among the genes surveyed, Pik-p emerged as the most widely distributed across the screened genotypes. It was followed closely by Piz, detected in 96.66 percent of the material, Pi40(t) at 93.33 percent, and Pi-ta at 90.00 percent. Several other important genes also appeared at notable frequencies, including Piz-t at 86.66 percent, Pi40 at 83.33 percent, and Pik at 73.33 percent. These genes are not interchangeable; each encodes a different intracellular immune receptor of the nucleotide-binding, leucine-rich repeat class that recognizes specific secreted proteins from the blast fungus, triggering a defensive hypersensitive response that halts pathogen spread.

The standout discoveries, however, were two genotypes named Itanagar and Tomila, which carried eleven different blast resistance genes each. That level of natural gene stacking is rare and makes these landraces exceptionally valuable as donor parents for breeding programs aiming to engineer durable resistance. Gene stacking is widely considered the most reliable strategy against blast because the fungus would need to simultaneously overcome multiple immune recognition systems to successfully infect the plant, a far more difficult evolutionary feat than defeating a single gene.

Close behind the top performers, seven additional genotypes each harbored ten resistance genes: Chakhao Poreiton, Chakhao Chandel-2, Liangneng Chakhao, Barbite rice, Hungyo, Chamiyak, and Lamyanba. The presence of multiple resistance genes in these traditional aromatic and local varieties is particularly encouraging because several of them, such as the Chakhao cultivars prized in Manipur for their distinctive aroma and cultural value, are already of economic and gastronomic importance. Improving their agronomic performance while retaining their intrinsic qualities becomes far easier when they already carry elite disease-resistance genetics.

The technical workflow behind these findings reflects standard best practice in modern plant pathology and genetics. High-molecular-weight genomic DNA was isolated from young leaf tissue, and polymerase chain reactions were run using primers specific to each resistance gene locus. Amplified fragments were then separated on agarose gels, and the presence or absence of the expected band sizes served as evidence for each gene. Combining this molecular passport with disease scores from the uniform blast nursery allowed the team to link genetic potential with actual field performance, a critical validation step that pure molecular screens sometimes lack.

The broader context of the work is equally important. Rice is the staple crop for billions of people, and Northeastern India is recognized as one of the centers of rice genetic diversity, home to landraces adapted to steep terrains, variable rainfall, and diverse pest pressures. Much of this diversity remains genetically uncharacterized, and as modern high-yielding varieties displace traditional cultivars, unique alleles risk being lost before their value is known. Studies like this one serve as both a rescue mission and a roadmap, documenting which resistance genes exist where, before that information and the germplasm itself disappear.

For breeders, the practical implications are immediate. The multi-gene genotypes identified here can be crossed with elite varieties and their offspring tracked using the same gene-specific markers, enabling precise introgression of resistance cassettes without dragging along undesirable traits. Gene pyramiding through marker-assisted backcrossing has already proven effective in improving Basmati and japonica rice cultivars elsewhere, and the Northeastern Indian donors identified in this study offer locally adapted, genetically diverse material for the same strategy. As blast continues to threaten rice production in a changing climate, the humble landraces of the region’s terraced hills may prove to be among the most important allies in keeping one of the world’s most vital food crops safe.

Subject of Research: Molecular screening of blast resistance genes in Northeastern Indian rice germplasm (Oryza sativa L.)

Article Title: Molecular Screening for Identification of Blast Resistance Genes in Northeastern Indian Rice Germplasm (Oryza sativa L.)

Article References: Singh, T. N., Saharia, D. D., Biswas, D., Devi, O. P., Pyngrope, A. H., Singh, N. B., Kh., P., Manjunath, P., Devi, T. R., Phurailatpam, S., Ngangkham, U., Devi, E. L., & Chongtham, S. K. (2026). Molecular Screening for Identification of Blast Resistance Genes in Northeastern Indian Rice Germplasm (Oryza sativa L.). Indian Journal of Genetics and Plant Breeding, 86(3), 292-302. https://doi.org/10.1007/s44489-026-00032-1

Image Credits: AI Generated

DOI: 10.1007/s44489-026-00032-1

Keywords: rice blast, Magnaporthe oryzae, blast resistance genes, Northeastern India, rice germplasm, marker-assisted selection, gene pyramiding, Oryza sativa, Pik-p, Pi40(t), landraces, plant breeding