Molecular Plant-Microbe Interactions® (MPMI)

Fig. 2. Generation of 2-fluoroadenine (2-FA)-resistant individuals of Aphanomyces euteiches.

Laurent Camborde et al. explored the applicability of DNA-free endogenous counterselection in filamentous oomycetes, using CRISPR-Cas9 ribonucleoproteins. Learn more: https://doi.org/10.1094/MPMI-05-25-0063-TA

Fig. 5. Nodule structure observation in soybean roots inoculated with HH103WT or HH103ΩmsbB, complementary (CE), or overexpression (OE) strains.

“A Lipopolysaccharide Lipid A Acyltransferase Gene msbB Is Involved in Soybean Rhizobial Intracellular Colonization and Symbiotic Nitrogen Fixation,” by Ziqi Li et al. Read now: https://doi.org/10.1094/MPMI-02-25-0018-R

Fig. 1. Schematic of pSymA and minSymA derivatives and both the stachydrine (stc) and trigonelline (trc) catabolism gene clusters.

Data from Garrett J. Levin et al. suggests that stachydrine catabolism contributes to optimal root nodule symbiosis between #Sinorhizobium meliloti and #Medicago sativa in the context of both a minimal and a wild-type genomic background. Learn more: https://doi.org/10.1094/MPMI-02-25-0021-SC

Fig. 4. Model for MoHTR1-mediated rice immune response. In this model, the MoHTR1 is secreted into the host cell via the biotrophic interfacial complex (BIC) and is translocated to the host nucleus. This nuclear translocation is facilitated by nuclear localization sequence (NLS), rice importin αs, and SUMOylation, a posttranslational modification. In the host nucleus, MoHTR1 suppresses the expression of OsMYB4, an immune response gene, by binding directly to the effector-binding element in its promoter. In addition, MoHTR1 interacted with OsSR45, a splicing factor in the nuclear speckles. MoHTR1 induces the alternative splicing of immune response-associated genes, orchestrating a sophisticated modulation of the rice immunity.

You-Jin Lim et al. highlight dual roles of MoHTR1 in regulating both transcription and posttranscriptional processes and provide novel insights into how nuclear effectors modulate host immunity through intricate molecular mechanisms. Learn more: https://doi.org/10.1094/MPMI-03-25-0033-SC

@lubegajib @niab-uk.bsky.social and I are thrilled to contribute to the global oat crown rust genomics study published in @mpmijournal.bsky.social. Thank you to @Figueroa_MM and @jsperschneider.bsky.social for leading, and the full author team for a superb collab. 🧬🌾 www.niab.com/news-views/n...

Fig. 7. STT3A is required for modification of RDA2.

Findings from Seowon Choi et al. suggest that STT3A contributes to plant immunity via posttranslational modification of proteins including NCER2 and RDA2. Learn more: https://doi.org/10.1094/MPMI-05-25-0061-R

Fig. 1. Powdery mildew infection phenology on Cabernet Sauvignon leaves and experimental design.

“Dual Single-Nucleus Gene Expression Atlas of Grapevine and Erysiphe necator During Early Powdery Mildew Infection,” by Maria-Sole Bonarota et al. Learn more: https://doi.org/10.1094/MPMI-08-25-0099-R

Fig. 4. Sweetpotato genotypes and wild relatives harbor a compact NRC-H subclade. Maximum likelihood (ML) phylogeny of complete coiled-coil nucleotide-binding and leucine-rich repeat immune receptor (CNL) proteins identified across all 35 sweetpotato and wild relative genotypes, using NB-ARC domain sequences as predicted by NLRtracker. Branches predicted to correspond to major nucleotide-binding and leucine-rich repeat receptor (NLR) required for cell death (NRC) helper and sensor clades (NRC-H, NRC-S) were highlighted based on phylogenetic placement of NRC0/1 (helpers, purple) and Hero-A, Rpi-amr3i, and Bs2 (sensors, green), respectively. Tips linked to CNLs containing integrated domains are labeled with yellow dots. The purple phylogenetic tree (right) includes only sequences from the indicated NRC-H lineage (left), underlining the Ipomoea batatas, I. trifida, I. triloba, and I. littoralis sequences phylogenetically predicted as helper NLRs.

C. H. Parada-Rojas et al. present a reference-quality NLRome for the hexaploid sweetpotato and diploid wild relatives. Learn more: https://doi.org/10.1094/MPMI-03-25-0034-R

Fig. 3. Bacterial co-occurrence networks in rice phyllosphere and rhizosphere. A to D, Co-occurrence network diagrams of bacterial communities in the phyllosphere and rhizosphere of Kitaake and rbl1Δ12 rice plants. Species compositions at the phylum level are indicated by dots of different colors, and interactions are shown by lines. Positive and negative correlations are shown by different colors as indicated.

Rice blast is caused by the fungus #Magnaporthe oryzae and seriously threatens rice production worldwide. Meng Liu et al. showed RBL1 shapes phyllosphere microbial structure to enhance disease resistance in rice: https://doi.org/10.1094/MPMI-08-25-0097-R

Fig. 1. Stages of arbuscular mycorrhizal symbiosis and associated conserved gene modules. Colonization of tissue—whether bryophyte thallus or flowering plant root cortex—involves many genes conserved across land plants. The process begins when the plant releases strigolactones (SLs), signaling molecules that fungi detect and that promote hyphal growth and branching toward the host tissue. Hyphae then enter individual cells and develop arbuscules, where nutrients are exchanged bidirectionally across the periarbuscular membrane (PAM). The plant genes controlling these processes are organized into conserved modules, shown in colored boxes. Genes in black text appear broadly in host genomes but are absent from nonhosts; white text indicates genes that are important for symbiosis and present in nonhost genomes.

Current Review: “Conservation of Genes Required for Arbuscular Mycorrhizal Symbiosis,” by Ellen Krall et al. Read now: https://doi.org/10.1094/MPMI-05-25-0065-CR

Fig. 1. Nitrogenase activity is not contingent upon total nodule mass or number. In the process of symbiotic nitrogen fixation, rhizobial nitrogenase converts atmospheric nitrogen gas into ammonia. Additionally, nitrogenase can fix acetylene gas into ethylene. This ability forms the basis of the acetylene reduction assay (ARA), commonly used to measure nitrogenase activity, an indicator of the level of nitrogen fixation occurring in root nodules.

To investigate the regulatory mechanisms governing symbiotic nitrogen fixation and senescence, Ryan DelPercio et al. conducted a temporal transcriptomic analysis of soybean nodules colonized with #Bradyrhizobium diazoefficiens USDA110. Learn more: https://doi.org/10.1094/MPMI-04-25-0037-R

Fig. 5. Analysis of response of Arabidopsis leaf ionome to Pseudomonas sp. CH267 (CH) and Burkholderia glumae PG1 (BG). The concentrations of elements were determined in Arabidopsis shoots treated with mock, CH, or BG by inductively coupled plasma mass spectrometry. The spider graph shows the log2 fold change between bacteria-treated plants and mock. Asterisks represent significant differences between bacterial treatments (red BG, blue CH) and mock at P < 0.05 (t test).

Findings from Anna Koprivova et al. uncovered the complex multilayered nature of #Arabidopsis responses to commensal and pathogenic bacteria and identify new connections across different regulatory levels. Learn more: https://doi.org/10.1094/MPMI-09-25-0125-R

Fig. 1. LRX1/2 negatively regulate rhizosphere fluorescent pseudomonad abundance.

Siyu Song et al. found that FERONIA kinase and LRX1/2 play an integral role in shaping the rhizosphere microbiome. Read the article to learn more: https://doi.org/10.1094/MPMI-05-25-0064-R

Fig. 3. Summary of resistance to Fusarium oxysporum f. sp. fragariae (Fof) and symptomology of yellows-fragariae and wilt-fragariae isolates. Left, FW1 recognizes SIX6 to confer resistance to yellows-fragariae Fof isolates, although it is unknown what type of protein FW1 encodes. FW2 to FW5 also confer resistance to yellows-fragariae isolates, but it is unknown what proteins they encode, and pathogen feature(s) are recognized. Middle, In the absence of FW1 to FW5, strawberry plants infected with yellows-fragariae isolates develop chlorosis and wilt (Henry et al. 2021). Right, Strawberry plants infected with wilt-fragariae isolates, which have SIX1 and SIX13 homologs (Czislowski et al. 2021; Jenner and Henry 2022), wilt but do not develop chlorosis (Henry et al. 2021).

Interactions Review: Mishi V. Vachev et al. summarize current knowledge, identify knowledge gaps, and provide a summary of genomic and molecular tools currently available to study the #Fusarium oxysporum f. sp. fragariae–strawberry interaction. Read now: https://doi.org/10.1094/MPMI-03-25-0028-IRW

Fig. 4. Geographic distribution of Macrophomina spp. genotype clusters. A, Isolates without a known state, province, or locality were assigned longitudes and latitudes at the midpoints of their respective sub-country region (Supplementary Table S1). Pie charts scaled to the number of isolates recovered are shown for locations that had multiple isolates. The color code for the pie charts is the same as provided for panel B of this figure. Minimum spanning trees for isolates in this study colored by B, genotype cluster or C, the country of origin.

Contrary to expectations, K. K. Pennerman et al. found that #Macrophomina phaseolina should be considered a single species with both specialist and generalist populations in which meiosis can maintain genetic diversity. Learn more: https://doi.org/10.1094/MPMI-03-25-0032-R

Fig. 4. Single gene and polycistronic transcripts shown for reannotated gene models (RGMs) ZtIPO323_010430 and ZtIPO323_010440. RGMs ZtIPO323_010430 and ZtIPO323_010440, located at chr_1: 2692944...2694593 and chr_1: 2694544...2697087, respectively, were transcribed on the same strand with overlapping 3′ untranslated region (UTR) and 5′ UTR (red rectangle).

Nicolas Lapalu et al. developed a new method to improve the prediction of eukaryotic genes and demonstrate its utility using the genome of the fungal wheat pathogen #Zymoseptoria tritici. Learn more: https://doi.org/10.1094/MPMI-07-25-0077-TA

Fig. 1. Schematic of the organization of an indeterminate nodule. The persistent meristem in indeterminate nodules produces a cylindrical shape with distinct zones (Vasse et al. 1990).

Editor’s Pick: “Non-Nitrogen-Fixing Sinorhizobium meliloti Can Escape Sanctions in Indeterminate Alfalfa Nodules, Exhibiting Parasitic Growth,” by Amanpreet K. Brar et al. Learn more: https://doi.org/10.1094/MPMI-06-25-0074-R

Fig. 3. A single L91Y amino acid substitution in AVRPM3a2/f2-A leads to recognition by the non-corresponding PM3b.

Editor’s Pick: "Interactions of Wheat Powdery Mildew Effectors Involved in Recognition by the Wheat NLR PM3," by Jonatan Isaksson et al. Learn more: https://doi.org/10.1094/MPMI-05-25-0050-SC

Fig. 1. The extended plant immune system. Schematic overview integrating key elements of classical plant immunity with microbiome-mediated protection, as discussed in this review. PTI, pattern-triggered immunity; ETI, effector-triggered immunity; SAR, systemic acquired resistance; ISR, induced systemic resistance; PGPR, plant growth-promoting rhizobacteria.

NEW H. H. Flor Distinguished Review: "The Extended Plant Immune System," by Corné M. J. Pieterse. Read the open access review in MPMI: https://doi.org/10.1094/MPMI-10-25-0144-HH

Fig. 6. Characterization of transgenic tomato plants (Pusa Ruby) overexpressing CpMSRB1.

Maniraj Rathinam et al. found the CpMSRB1 gene in a wild pigeonpea acts as a molecular "repairman," protecting a key enzyme to ramp up antioxidants and defense chemicals against the devastating pod borer. Future pest resistance starts here. Learn more: https://doi.org/10.1094/MPMI-11-24-0149-R

Fig. 1. Putative candidate genes involved in spring black stem and leaf spot (SBS) disease resistance in Medicago truncatula.

Jacob R. Botkin and Shaun J. Curtin engineered Medicago plants using CRISPR-Cas9 and gene overexpression and reported enhanced resistance (up to 80%) to the devastating Spring Black Stem fungus. This research paves the way for resistant alfalfa. Learn more: https://doi.org/10.1094/MPMI-05-25-0053-R

Fig. 4. Proteins in the Pmk1 and Mps1 mitogen-activated protein kinase (MAPK) cascades were required for Diaporthe amygdali virulence.

Lina Yang et al. cracked the signal pathways used by peach shoot blight fungus, Diaporthe amygdali. Targeting the Pmk1 and Mps1 cascades cripples the pathogen’s growth and ability to infect. This is a key step for new disease control! Learn more: https://doi.org/10.1094/MPMI-06-25-0071-R

Fig. 1. Confocal laser scanning microscopy (CLSM) images of Aegilops cylindrica leaves infected with IPO323 (incompatible) and Zt469 (compatible) Zymoseptoria tritici isolates. Microscopic images from CLSM analysis using maximum projections of image z-stacks. Cell nuclei and plant tissue are visible in purple, and fungal hyphae are in green. Except for the 4 days postinfection (dpi) sample of the incompatible interaction, only fungal hyphae growing within the plant tissue are shown. Letters indicate which infection stage is represented by the images. Time points listed in purple were chosen for RNA sequencing analysis

Rune Hansen et al. reported that the substomatal cavity is a crucial check point where the devastating Septoria blotch (Zymoseptoria tritici) infection is stopped. Understanding this mechanism is key to future wheat immunity. Learn more: https://doi.org/10.1094/MPMI-11-24-0147-R

Fig. 1. Population structure of Phytophthora cinnamomi observed on avocado in California and Mexico.

Research by Aidan C. Shands et al. on Phytophthora root rot in California avocados revealed that the pathogen, P. cinnamomi, likely migrated from Mexico. Learn more: https://bit.ly/4hxxsdA

Fig. 1. Pseudomonas syringae pv. tomato DC3000 polymutant D36E is a suitable candidate for effector screens in spinach.

Melanie Mendel et al. developed a new Type 3 Secretion System (T3SS) tool to study how Pseudomonas syringae effectors invade spinach. They identified AvrE1 and HopM1 as key virulence factors. This is a vital step for breeding disease-resistant leafy greens. Learn more: https://bit.ly/4nrvqgn

Fig. 3. Confirmation of the expression of putative CsLOB1 target genes driven by designer transcription activator-like effectors (dTALEs).

Rikky Rai and Nian Wang report that Xanthomonas effector PthA4 indirectly triggers the disease by activating a host gene, which then switches on plant genes (CsEXP2 and CsEG1) that lead to the destructive canker symptoms. This pinpoints new targets for breeding resistance: https://bit.ly/47FUg6C

Fig. 2. Structural variation at avirulence (Avr) loci in CH5. The figure shows synteny plots between the C and H haplotypes at the AvrM, AvrL567, AvrL2, and AvrP123 loci. Genes are labeled with their identifiers, and NA stands for “not annotated” in the gene annotation. Repetitive elements are shown in green boxes. Separate scale bars are shown to the left of each locus. Shaded boxes connect haplotype regions of conserved sequence. Effector genes are marked with a black star.

Jana Sperschneider et al. reported a new, high-quality genome assembly of the flax rust fungus (Melampsora lini) resolved complex effector loci and confirmed 2 unusually large effector proteins, AvrM3 and AvrN. This challenges the standard idea that effectors must be small: https://bit.ly/3Jpr37O

Fig. 2. Deletion of FgRGAE reduces wheat infection at early time points. A, FgRGAE::HygR mutants M27 and M36 both significantly reduced disease severity at 4 days postinfection (dpi) in wheat cultivar Alsen. At 7 dpi, the difference was not statistically significant. B, Toxin deoxynivalenol (DON) was not significantly different at 7 dpi. C, Representative pictures showing less severe Fusarium head blight symptoms observed on Alsen heads infected with FgRGAE::HygR M27 mutant than the wild type. Bars represent the average and standard error of 24 inoculated wheat heads with each strain. Different letters indicate a significant difference at the P < 0.05 level by one-way analysis of variance.

Nicholas Rhoades et al. identified an RGAE homolog in Fusarium graminearum that is critical for the initial infection and DON mycotoxin accumulation in wheat and barley. Targeting this single effector gene, FgRGAE, offers a powerful new strategy to protect cereal crops: https://bit.ly/4oilO96

Fig. 3. Mapping of the most significantly represented viral small-interfering RNAs (vsiRNAs) to the grapevine red blotch virus (GRBV) genome (NY358 to JQ901105.2). A, Linear representation of the GRBV genomic features (open reading frames [ORFs] and intergenic regions) and the location of RNA interference (RNAi) hotspots (HSs). The genomic features are labeled as follows: long intergenic region (LIR), coat protein (V1 or CP), short intergenic region (SIR), and replication-associated protein (C1 or RepA). B, Predicted secondary structures for each HS. The color coding on these structures, generated by RNAfold, reflects the entropy at each position, indicating the binding stability between base pairs (red = high stability, green/blue = low stability).

Mandelli & Deluc identified 9 "hotspots" on the Grapevine Red Blotch Virus genome that are highly targeted by the grapevine's defense system. Delivering double-stranded RNA from these sites significantly reduced viral expression, paving the way for targeted RNAi biopesticides: https://bit.ly/3Jvwr9e

Fig. 6. Localization of signal peptide (SP)-yellow fluorescent protein (YFP) and AvrM1-105-YFP in flax leaves infected with the respective transgenic Melampsora lini strains. Representative confocal images showing localization of A, SP-YFP; B, cyan fluorescent protein (CFP); and C and D, AvrM1-105-YFP. YFP fluorescence is shown in yellow, chloroplast autofluorescence in red, and CFP fluorescence in cyan. Scale bars indicate 10 µm. Hy, hyphae; Ha, haustorium; Cy, flax cytoplasm; Nu, flax nucleus.

Xiaoxiao Zhang et al. reports that flax rust effectors are secreted into a space outside the host cell, but only AvrM has the key signal for delivery into the host cell cytoplasm. Translocation is a separate process! Learn more: https://bit.ly/47BTl6Z

Read the commentary: https://bit.ly/4oO50Xj