Biology subjects

Talbot, N. J.

Publications and source records attributed to Talbot, N. J..

At least 19 recordsLinked to original sources

bioRxiv2026

A Blast Fungus Effector Targets a Tubby-like F-box Protein to Suppress Plant Immunity

The blast fungus Magnaporthe oryzae is one of the most destructive pathogens of rice, secreting effector proteins that reprogram host cells to enable infection. Identifying plant targets of these fungal effectors is central to understanding how blast disease is established, but the targets and mechanisms of most effectors remain unknown. Here, we show that a Zinc finger (ZiF)-family effector, Tie1, targets the rice Tubby-like protein (TLP) family, which are membrane-associated plant immunity regulators whose exact functions have not been defined. Tie1 binds a range of rice TLPs and specifically engages with the Tubby-like domain of OsTLP7. Co-expression in planta with Tie1 re-localises this domain from the plasma membrane to the cytoplasm and nucleus, a shift also observed by disrupting the OsTLP7 phosphatidylinositol 4,5-bisphosphate (PIP2)-binding site in the absence of the effector. By combining AlphaFold3 structural predictions with allelic variation, we define a putative Tie1/OsTLP7 interface distal to the PIP2-binding site. Furthermore, Tie1 induces transcriptional activation activity of the OsTLP7 Tubby-like domain, and Tie1 overexpression in stable Arabidopsis lines leads to upregulation of genes that repress jasmonic acid (JA) signalling. Taken together, our results indicate that Tie1 inhibits PIP2 binding by OsTLP7 to drive its re-localisation to the nucleus and thereby modulating transcription to suppress JA-mediated plant immunity.

plant biology↗

bioRxiv2026

A Pmk1-Regulated Mst12-Bip1 Network Coordinates Appressorium Function, Effector Deployment, and Invasive Growth by Magnaporthe oryzae

To cause rice blast disease, the filamentous fungus Magnaporthe oryzae develops a specialised infection cell called an appressorium, which generates enormous turgor to breach the rice leaf cuticle. Although key regulators of appressorium development have been identified, it is not known how they drive the extensive transcriptional reprogramming required for infection-related morphogenesis. Here, we show that the Pmk1 MAP kinase orchestrates plant infection by regulating a transcriptional network controlled by the Mst12 and Bip1 transcription factors. Bip1 is regulated both by Pmk1-dependent phosphorylation and at the transcriptional level, while Mst12 binds to a cis-acting element upstream of BIP1 essential for pathogenesis. Bip1 and Mst12 are both necessary for regulating a set of Pmk1-dependent appressorium-specific genes, including transcriptional regulators, cell wall-degrading enzymes, and effector proteins. In addition, Mst12 specifically regulates functions required for appressorium-mediated penetration, while Bip1 controls a distinct sub-set of effector genes deployed during invasion of plant tissue. When considered together, these findings define a Pmk1-dependent transcriptional network required for plant infection by the blast fungus.

molecular biology↗

bioRxiv2026

Computational design of de novo integrated domains enables rational control of pathogen effector recognition in plant NLR immune receptors.

The rapid evolution of plant pathogens poses a persistent threat to global agricultural sustainability, often outpacing the discovery and deployment of natural disease resistance genes. While bioengineering of plant intracellular immune receptors (NLRs) offers a potential solution, developing bespoke immune recognition remains constrained by the laborious characterisation of natural receptors and plant-pathogen interactions. Here, we describe a programmable framework that leverages generative AI protein design tools, RFdiffusion and ProteinMPNN, to design de novo integrated domains (IDs) against diverse pathogen effectors. By integrating these bespoke binders into the modular rice blast Pik-1/Pik-2 NLR receptor chassis, we successfully engineer recognition of a non-cognate virulence factor (effector) from the Panama disease pathogen, Fusarium oxysporum f. sp. cubense Tropical Race 4. Functional assays in Nicotiana benthamiana demonstrate that these de novo domains facilitate specific effector perception and initiate immune signalling, while structural and biophysical analyses confirm that de novo integrated domains maintain high structural fidelity to the initial designs and associate with their targets via the predicted interaction interfaces. Additionally, our findings provide orthogonal evidence for the role of integrated domains in regulation of NLR signalling, demonstrating integration of de novo IDs can either trigger autoactivity or, in some cases, lead to effector-mediated repression of cell death. By decoupling immune perception from natural evolutionary history through deploying AI-designed sensory domains, this work establishes a design-lead framework for generation of programmable plant immune receptors, providing a new avenue for bioengineering crops against emerging pathogens.

plant biology↗

bioRxiv2026

Colletotrichum higginsianum effector ChEC108 binds a plasmodesmal HMA protein and elicits plant defence

To establish infection, phytopathogens deploy effectors to compromise host defences and facilitate invasive growth. As part of this, the battle for control of symplastic connectivity via plasmodesmata is a key determinant of infection outcomes, yet little is known about how fungal effectors directly exploit these channels, and in turn, how hosts defend them. Here, we have identified ChEC108 as a plasmodesmal-targeting, cell-to-cell mobile effector from the anthracnose fungus, Colletotrichum higginsianum. ChEC108 binds the plasmodesmal protein HEAVY METAL-ASSOCIATED (HMA) ISOPRENYLATED PLANT PROTEIN 6 (HIPP6) from Arabidopsis via a tetrahedral metal ion coordination site with either of its HMA domains. Constitutive in planta expression of ChEC108 induces plasmodesmal closure and the upregulation of defence-associated genes in a manner dependent on its capacity to bind HIPP6. Further, HIPP6 binding impairs cell-to-cell mobility of ChEC108. Alongside the finding that loss of ChEC108 favoured C. higginsianum infection, this suggests ChEC108-HIPP6 interaction at plasmodesmata positively regulates defence.

plant biology↗

bioRxiv2026

A stage-resolved map of dynamic septin interactions required for infection by the rice blast fungus

Septin GTPases are essential cytoskeletal regulators that organize membranes and scaffold protein complexes to control cytokinesis, polarity, and morphogenesis. How septins execute these functions remains poorly understood, and comprehensive, stage-resolved interaction maps are lacking. Here, we define a quantitative, time-resolved septin interactome in the rice blast fungus Magnaporthe oryzae using immunoprecipitation coupled to mass spectrometry. We map more than 350 interactors of septins Sep3, Sep4, Sep5 and Sep6, revealing a dynamic network required for appressorium-mediated plant infection. Beyond canonical roles in cytoskeletal organisation and polarity, septins associate with proteins linked to membrane remodelling, metabolism, and virulence, deployed during host invasion. Integration with ultra-high-throughput yeast two-hybrid analysis defines a high-confidence septin interactome and identifies previously uncharacterised factors, including Msi1, a BAR domain protein required for invasive growth. Together, these findings establish septins as dynamic organisers of infection-related processes and provide a framework for understanding how cytoskeletal scaffolds coordinate fungal pathogenesis.

cell biology↗

bioRxiv2025

Tangerine: a Starship-like element in the genomes of Xanthoria lichen-forming fungi

Lichens are symbiotic associations between filamentous fungi and photosynthetic micro-organisms, such as green algae and/or cyanobacteria, that result in a single anatomically-complex structure that can thrive in environments inhospitable to most organisms, including arctic tundra, high mountains, and deserts. Recent evidence suggests that lichens may be even more complex than previously appreciated, containing multiple microbial constituents, but how genomes of the principal fungal symbiont (which provides the majority of biomass in lichen tissue) have been shaped during evolution is largely unexplored. Recently, giant transposable elements called Starships have been found in many genomes of filamentous fungi, but to which extent they occur in lichen-forming fungi is not known. In this report, we describe a Starship element from the lichen fungus Xanthoria parietina. This element, named Tangerine, contains several genes that have signatures of horizontal gene transfer from non-lichen-forming fungi, most likely from black yeasts of the Chaetothyriales, that are often lichen-associated. Repetitive sequences carried by Tangerine, and found in other sites in Xanthoria genomes, are affected by repeat-induced point mutation (RIP), a mechanism of genome defense against transposable elements, consistent with fungal sexual reproduction which always precedes new lichen formation by Xanthoria. Tangerines "captain" belongs to a newly defined family of tyrosine recombinases specific to lichen-forming Lecanoromycetes. Several other captain clades have signatures of horizontal gene transfer between distantly related lichen-forming fungi and non-mycobiont lichen-associated fungi. We speculate that Starships may play a significant, yet hitherto unrecognized role, in lichen genome evolution and provide a roadmap for further investigation.

genomics↗

bioRxiv2025

Synchronous spatio-temporal control of autophagy and organelle trafficking is necessary for appressorium-mediated plant infection by Magnaporthe oryzae

The blast fungus Magnaporthe oryzae infects plants using a specialised infection structure called an appressorium that generates physical force to break the rice leaf cuticle. Appressorium development follows a cell cycle-controlled morphogenetic program, requiring autophagy-associated cell death of the fungal spore from which the infection cell develops. How proliferative growth of the fungus is regulated at the same time as programmed cell death, however, is unknown. In this study, we provide evidence that each cell of the conidium undergoes a separate developmental program, which is necessary for plant infection. Using quantitative live-cell imaging, we monitored trafficking of ten organelle types during appressorium morphogenesis in a wild-type M. oryzae strain and isogenic {Delta}atg8 autophagic mutant. High-resolution microscopy using a photoactivatable green fluorescent protein revealed that organelle trafficking occurs from a single conidium cell into the appressorium, while the remaining two cells undergo autophagy. Organelle inheritance operates independently of cell cycle checkpoints but is always associated with spore germination. We furthermore defined the temporal sequence of organelle movement and de novo organelle biogenesis in the incipient appressorium using photoconvertible fluorescent localisation microscopy. Taken together, our study reveals how synchronous spatiotemporal control of autophagy and organelle trafficking is necessary for rice blast infection.

molecular biology↗

bioRxiv2025

Chromosome-level genome assembly of the photobiont alga Trebouxia sp. 'A48' from Xanthoria parietina provides new insight into the lichen symbiosis

O_LILichens are symbiotic assemblies consisting of multiple organisms, chiefly a fungus and a photosynthetic microorganism or the photobiont. Among diverse photobionts, the most prevalent is the chlorophyte alga Trebouxia. C_LIO_LIWe produced a chromosome-level assembly of Trebouxia sp. A48, a photobiont of Xanthoria parietina. The genome was assembled into 20 contigs, of which 16 had telomeric repeats on both ends and likely represent complete chromosomes. We compared the genome to genomes of other Trebouxia species and analyzed it to investigate the biology of the species, including its lifecycle and adaptations to lichen lifestyle. C_LIO_LITrebouxia sp. A48 genome is haploid and encodes genes involved in sexual reproduction and meiosis. The predicted secretome is enriched in hydrolases and redox enzymes and contains carbohydrate-binding proteins potentially involved in cell-to-cell recognition and adhesion. We identified genes potentially involved in carbon concentrating and confirmed two instances of ancient horizontal gene transfer from fungi. C_LIO_LIThe genome and the strain of Trebouxia sp. A48 are available for the community for research on algal evolution and lichen symbiosis. C_LI

genomics↗

bioRxiv2024

Multipartite complexity of the lichen symbiosis revealed by metagenome and transcriptome analysis of Xanthoria parietina

Lichens are composite symbiotic associations of fungi, algae, and bacteria that result in large, anatomically complex organisms adapted to many of the worlds most challenging environments. How such intricate, self-replicating lichen architectures develop from simple microbial components remains unknown because of their recalcitrance to experimental manipulation. Here we report a metagenomic and metatranscriptomic analysis of the lichen Xanthoria parietina at different developmental stages. We identified 168 genomes of symbionts and lichen-associated microbes within a lichen thallus, including representatives of green algae, three different classes of fungi, and 14 bacterial phyla. By analyzing occurrence of individual species across lichen thalli from diverse environments, we defined both substrate-specific and core microbial components of the lichen. Meta-transcriptomic analysis of the principal fungal symbiont from three different developmental stages of a lichen, compared to axenically grown fungus, revealed differential gene expression profiles indicative of lichen-specific transporter functions, specific cell signalling, transcriptional regulation and secondary metabolic capacity. Putative immunity-related proteins and lichen-specific structurally conserved secreted proteins resembling fungal pathogen effectors were also identified, consistent with a role for immunity modulation in lichen morphogenesis.

bioinformatics↗

bioRxiv2024

Molecular mimicry of a pathogen virulence target by a plant immune receptor

Plants and animals respond to pathogen attack by mounting innate immune responses that require intracellular nucleotide binding leucine-rich repeat (NLR) proteins. These immune receptors detect pathogen infection by sensing virulence effector proteins. However, the mechanisms by which receptors evolve new recognition specificities remain poorly understood. Here we report that a plant NLR has evolved the capacity to bind to a pathogen effector by acting as a molecular mimic of a virulence target of the effector, thereby triggering an immune response. The barley NLR Mildew Locus A 3 (MLA3) confers resistance to the blast fungus Magnaporthe oryzae by recognizing the effector Pwl2. Using structural analysis, we show that MLA3 has acquired the capacity to bind and respond to Pwl2 through molecular mimicry of the effector host target HIPP43. We demonstrate that the amino acids at the binding interface of MLA3 and Pwl2 are highly conserved in interface of HIPP43 with Pwl2, and are required to trigger an immune response. We used this discovery to bioengineer SR50--an MLA ortholog in rye that confers resistance to wheat stem rust--by introducing the Pwl2 binding interface of MLA3. This chimeric receptor has dual recognition activities, binding and responding to effectors from two major cereal pathogens. Collectively, these results provide evidence that plant immune receptors have evolved sophisticated mimicry strategies to counteract pathogen attack.

plant biology↗

bioRxiv2024

Bioengineering a plant NLR immune receptor with a robust binding interface towards a conserved fungal pathogen effector

Bioengineering of plant immune receptors has emerged as a key strategy for generating novel disease resistance traits to counteract the expanding threat of plant pathogens to global food security. However, current approaches are limited by rapid evolution of plant pathogens in the field and may lack durability when deployed. Here, we show that the rice nucleotide-binding, leucine-rich repeat (NLR) immune receptor Pik-1 can be engineered to respond to a conserved family of effectors from the multihost blast fungus pathogen Magnaporthe oryzae. We switched the effector binding and response profile of the Pik NLR from its cognate rice blast effector AVR-Pik to the host-determining factor Pwl2 by installing a putative host target, OsHIPP43, in place of the native integrated HMA domain (generating Pikm-1OsHIPP43). This chimeric receptor also responded to other PWL alleles from diverse blast isolates. The crystal structure of the Pwl2/OsHIPP43 complex revealed a multifaceted, robust interface that cannot be easily disrupted by mutagenesis, and may therefore provide durable, broad resistance to blast isolates carrying PWL effectors in the field. Our findings highlight how the host targets of pathogen effectors can be used to bioengineer new recognition specificities that have more robust properties compared to naturally evolved disease resistance genes.

plant biology↗

bioRxiv2024

The blast effector Pwl2 is a virulence factor that modifies the cellular localisation of host protein HIPP43 to suppress immunity.

The rice blast fungus Magnaporthe oryzae secretes a battery of effector proteins to facilitate host infection. Among these effectors, Pwl2 was first identified as a host specificity determinant for infection of weeping lovegrass (Eragrostis curvula) and is also recognised by the barley Mla3 resistance gene. However, its biological activity is not known. Here we show that PWL2 expression is regulated by the Pmk1 MAP kinase during cell-to-cell movement by M. oryzae at plasmodesmata (PD)-containing pit field sites. Consistent with its regulation, we provide evidence that Pwl2 binds to a barley heavy metal-binding isoprenylated protein HIPP43, which results in its displacement from plasmodesmata. Transgenic barley lines overexpressing either PWL2 or HIPP43 exhibit attenuated immune responses and increased disease susceptibility. By contrast, a Pwl2SNDEYWY mutant that does not interact with HIPP43, fails to alter the PD localisation of HIPP43. Targeted deletion of three copies of PWL2 in M. oryzae results in a{Delta} pwl2 mutant showing gain-of-virulence to weeping lovegrass and barley Mla3 lines, but also a reduction in severity of blast disease on susceptible host plants. Taken together, our results provide evidence that Pwl2 is a virulence factor that acts by suppressing host immunity through perturbing the plasmodesmatal deployment of HIPP43.

plant biology↗

bioRxiv2023

Zinc-finger (ZiF) fold secreted effectors form a functionally diverse family across lineages of the blast fungus Magnaporthe oryzae.

Filamentous plant pathogens deliver effector proteins into host cells to suppress host defence responses and manipulate metabolic processes to support colonization. Understanding the evolution and molecular function of these effectors provides knowledge about pathogenesis and can suggest novel strategies to reduce damage caused by pathogens. However, effector proteins are highly variable, share weak sequence similarity and, although they can be grouped according to their structure, only a few structurally conserved effector families have been functionally characterized to date. Here, we demonstrate that Zinc-finger fold (ZiF) secreted proteins form a functionally diverse effector family in the blast fungus Magnaporthe oryzae. This family relies on the Zinc-finger motif for protein stability and is ubiquitously present, forming different effector tribes in blast fungus lineages infecting 13 different host species. Homologs of the canonical ZiF effector, AVR-Pii from rice infecting isolates, are present in multiple M. oryzae lineages, and the wheat infecting strains of the fungus, for example, possess an allele that also binds host Exo70 proteins and activates the immune receptor Pii. Furthermore, ZiF tribes vary in the host Exo70 proteins they bind, indicating functional diversification and an intricate effector/host interactome. Altogether, we uncovered a new effector family with a common protein fold that has functionally diversified in lineages of M. oryzae. This work expands our understanding of the diversity of M. oryzae effectors, the molecular basis of plant pathogenesis and may ultimately facilitate the development of new sources for pathogen resistance. Author SummaryDiseases caused by filamentous plant pathogens impact global food production, leading to severe economic and humanitarian consequences. These pathogens secrete hundreds of effectors inside the host to alter cellular processes and to promote infection and disease. Effector proteins have weak or no sequence similarity but can be grouped in structural families based on conserved protein folds. However, very few conserved effector families have been functionally characterized. We have identified a family of effectors with a shared Zinc-finger protein fold (ZiF) that is present in lineages of the blast fungus Magnaporthe oryzae that can, collectively, infect 13 different grasses. We characterized the binding of a sub-set of these proteins to putative Exo70 host targets and showed they can be recognized by the plant immune system. Furthermore, we show that other ZiF effectors do not bind Exo70 targets, suggesting functional specialization within this effector family for alternative interactors. These findings shed light on the diversity of effectors and their molecular functions, as well as potentially leading to the development of new sources of blast disease resistance in the future.

plant biology↗

bioRxiv2023

Duplication and neofunctionalization of a horizontally-transferred xyloglucanase as a facet of the red queen co-evolutionary dynamic

Oomycetes are heterotrophic protists that share phenotypic similarities with fungi, including the ability to cause plant diseases, but branch in a separate and distant region of the eukaryotic tree of life. It has been suggested that multiple horizontal gene transfers (HGTs) from fungi-to-oomycetes contributed to the evolution of plant-pathogenic traits. These HGTs are predicted to include secreted proteins that degrade plant cell walls. This is a key trait in the pathology of many oomycetes, as the plant cell wall represents a primary barrier to pathogen invasion and a rich source of carbohydrates. Many of the HGT gene families identified have undergone multiple rounds of duplication. Using a combination of phylogenomic analysis and functional assays, we investigate the diversification of a horizontally-transferred xyloglucanase gene family in the model oomycete species Phytophthora sojae. Our analyses detect 11 genes retained in P. sojae among a complex pattern of gene duplications and losses. Using a phenotype assay, based on heterologous expression in yeast, we show that eight of these paralogs have xyloglucanase function, including variants with distinct protein characteristics, such as a long-disordered C-terminal extension that can increase xyloglucanase activity. The functional xyloglucanase variants analysed subtend an ancestral node close to the fungi-oomycetes gene transfer, suggesting the horizontally-transferred gene was a bona fide xyloglucanase. Expression of xyloglucanase paralogs in Nicotiana benthamiana triggers distinct patterns of reactive oxygen species (ROS) generation, demonstrating that enzyme variants differentially stimulate pattern-triggered immunity in plants. Mass spectrometry of detectable enzymatic products demonstrates that some paralogs catalyze production of variant breakdown profiles, suggesting that secretion of multiple xyloglucanase variants increases efficiency of xyloglucan breakdown, as well as potentially diversifying the range of Damage-Associated Molecular Patterns (DAMPs) released during pathogen attack. We suggest that such patterns of protein neofunctionalization, and variant host responses, represent an aspect of the Red Queen host-pathogen co-evolutionary dynamic. Significance StatementThe oomycetes are a diverse group of eukaryotic microbes that include some of the most devastating pathogens of plants. Oomycetes perceive, invade, and colonize plants in similar ways to fungi, in part because they acquired the genes to attack and feed on plants from fungi. These genes are predicted to be useful to oomycete plant pathogens because they have undergone multiple rounds of gene duplication. One key enzyme for attacking plant cell wall structures is called xyloglucanase. Xyloglucanase in the oomycetes has undergone multiple rounds of gene duplication, leading to variants including an enzyme with a C-terminal extension that increases activity. Some xyloglucanase variants trigger unique patterns of reactive oxygen species (ROS) in planta, and generate different profiles of cell wall breakdown products - such outcomes could act to mystify and increase the workload of the plant immune system, allowing successful pathogens to proliferate.

evolutionary biology↗

bioRxiv2023

Genomic analysis of Coccomyxa viridis, a common low-abundance alga associated with lichen symbioses

Lichen symbiosis is centered around a relationship between a fungus and a photosynthetic microbe, usually a green alga. In addition to their main photosynthetic partner (the photobiont), lichen symbioses can contain additional algae present in low abundance. The biology of these algae and the way they interact with the rest of lichen symbionts remains largely unknown. Here we present the first genome sequence of a non-photobiont lichen-associated alga. Coccomyxa viridis was unexpectedly found in 12% of publicly available lichen metagenomes. With few exceptions, members of the Coccomyxa viridis clade occur in lichens as non-photobionts, potentially growing in thalli endophytically. The 45.7 Mbp genome of C. viridis was assembled into 18 near chromosome-level contigs, making it one of the most contiguous genomic assemblies for any lichen-associated algae. Comparing the C. viridis genome to its close relatives revealed the presence of traits associated with the lichen lifestyle. The genome of C. viridis provides a new resource for exploring the evolution of the lichen symbiosis, and how symbiotic lifestyles shaped evolution in green algae.

microbiology↗

bioRxiv2023

The phosphorylation landscape of infection-related development by the rice blast fungus

Many of the worlds most devastating crop diseases are caused by fungal pathogens which elaborate specialized infection structures to invade plant tissue. Here we present a quantitative mass spectrometry-based phosphoproteomic analysis of infection-related development by the rice blast fungus Magnaporthe oryzae, which threatens global food security. We mapped 8,005 phosphosites on 2,062 fungal proteins, revealing major re-wiring of phosphorylation-based signaling cascades during fungal infection. Comparing phosphosite conservation across 41 fungal species reveals phosphorylation signatures specifically associated with biotrophic and hemibiotrophic fungal infection. We then used parallel reaction monitoring to identify phosphoproteins directly regulated by the Pmk1 MAP kinase that controls plant infection by M. oryzae. We define 33 substrates of Pmk1 and show that Pmk1-dependent phosphorylation of a newly identified regulator, Vts1, is required for rice blast disease. Defining the phosphorylation landscape of infection therefore identifies potential therapeutic interventions for control of plant diseases.

plant biology↗

bioRxiv2022

Barley MLA3 recognizes the host-specificity determinant PWL2 from rice blast (M. oryzae)

Plant nucleotide-binding leucine-rich repeat immune receptors (NLRs) directly or indirectly recognize pathogen-secreted effector molecules to initiate plant defense. Recognition of multiple pathogens by a single NLR is rare and usually occurs via monitoring for changes to host proteins; few characterized NLRs have been shown to recognize multiple effectors. The barley NLR Mla has undergone functional diversification and Mla alleles recognize host-adapted isolates of barley powdery mildew (Blumeria graminis f. sp. hordei; Bgh). Here, we show that Mla3 also confers resistance to rice blast (Magnaporthe oryzae) in a dosage dependent manner. Using a forward genetic screen, we discovered that the recognized effector from M. oryzae is PWL2, a host range determinant factor that prevents M. oryzae from infecting weeping lovegrass (Eragrostis curvula). Mla3 has therefore convergently evolved the capacity to recognize effectors from diverse pathogens.

plant biology↗

bioRxiv2022

Rgs1 is a regulator of effector gene expression during plant infection by the rice blast fungus Magnaporthe oryzae

To cause rice blast disease the filamentous fungus Magnaporthe oryzae secretes a battery of effector proteins into host plant tissue to facilitate infection. Effector-encoding genes are expressed only during plant infection and show very low expression during other developmental stages. How effector gene expression is regulated in such a precise manner during invasive growth by M. oryzae is not known. Here, we report a forward-genetic screen to identify regulators of effector gene expression, based on selection of mutants that show constitutive effector gene expression. Using this simple screen, we identify Rgs1, a regulator of G-protein signalling (RGS) protein that is necessary for appressorium development, as a novel transcriptional regulator of effector gene expression, which acts prior to plant infection. We show that an N-terminal domain of Rgs1, possessing transactivation activity, is required for effector gene regulation and acts in an RGS-independent manner. Rgs1 controls expression of at least 60 temporally co-regulated effector genes, preventing their transcription during the pre-penetration stage of development prior to plant infection. A regulator of appressorium morphogenesis is therefore also required for orchestration of pathogen gene expression required for invasive growth by M. oryzae during plant infection.

molecular biology↗