Molecular Plant-microbe Interactions最新文献

Slippery skin of onion caused by Burkholderia gladioli pv. alliicola (Bga) is a common bacterial disease reported from onion-growing regions around the world. Despite the increasing attention in recent years, our understanding of the virulence mechanisms of this pathogen remains limited. In this study, we characterized the predicted genetic determinants of virulence in Bga strain 20GA0385 using a reverse genetics approach. Using the closely related rice pathogen B. glumae as a reference, comparative genomics analysis was performed to identify Bga candidate virulence factors and regulators. Marked and unmarked deletion mutants were generated using allelic exchange, and the mutants were functionally validated using in vitro and in vivo assays. The role of mutants in pathogenic phenotypes was analyzed using onion foliar/seedling necrosis assays, the red scale necrosis assay, and in planta bacterial population counts. The phytotoxin toxoflavin was a major contributor to foliar necrosis and bacterial populations, whereas the type II and type III secretion systems (T2SS/T3SS) were dispensable for foliar symptoms. In onion scale tissue, the T2SS single mutant gspC and its double and triple mutant derivatives all contributed to scale lesion area. Neither the lipocyclopeptide icosalide, toxoflavin, nor T3SS was required for scale symptoms. Our results suggest that the quorum sensing tofIMR system in Bga regulates toxoflavin, T2SS, and T3SS, contributing to onion symptom production. We show that different virulence factors contribute to onion tissue-specific virulence patterns in Bga and that decreases in scale symptoms often do not result in decreased Bga populations in onion tissue. [Formula: see text] Copyright © 2025 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Zymoseptoria tritici is a cosmopolitan hemibiotrophic wheat pathogen with a high mutation rate and a mixed reproduction system, with sexual and asexual cycles occurring within the same disease cycle. This leads to challenges in traditional farming management. For successful integrated pest management, especially for surveys of new aggressive lineages, it is critical to understand population diversity in the field. We look at whole-genome sequence data for three datasets to differentiate within field diversity in fields of similar size: one dataset from a newly sampled field population from the United Kingdom and two publicly available datasets from fields from the United States and Switzerland. This survey of genetic variation allows us to describe in detail how variable the field populations are and offers insight into the dynamics of the disease in a snapshot per field. Inspection of population structure and diversity features, such as minor allele frequency distribution and clonality, show no within-field structure, the most abundant single-nucleotide polymorphisms are present in low frequency, and European fields have higher clonality. Knowing that effectors play particularly important roles in (a)virulence, we specifically assess effector diversity characteristics. On a whole-genome scale, we can see separation of the populations at the regional scale, but we do not find such separation for the effectors. Moreover, we find that multiple effector haplotypes can be found interspersed within the field and even occur within what have been considered clonal isolates or isolates from a single lesion. Our analyses highlight that within-field Z. tritici genetic variation is higher than previously reported. Our finding that multiple effector haplotypes can be found within a single lesion might explain the large resistance gene-breaking potential of Z. tritici. [Formula: see text] Copyright © 2025 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Members of the Phytophthora genus are responsible for many important diseases in agricultural and natural ecosystems. Phytophthora ramorum causes devastating diseases of oak and tanoak stands in U.S. forests and larch in the United Kingdom. The four evolutionary lineages involved express different virulence phenotypes on plant hosts, and characterization of gene content is foundational to understanding the basis for these differences. Recent discovery of P. ramorum at its candidate center of origin in Asia provides a new opportunity for investigating the evolutionary history of the species. We assembled high-quality genome sequences of six P. ramorum isolates representing three lineages from Asia and three causing epidemics in Western U.S. forests. The six genomes were assembled into 13 putative chromosomes. Analysis of structural variation revealed multiple chromosome fusion and fission events. Analysis of putative virulence genes revealed variations in effector gene composition among the sequenced lineages. We further characterized their evolutionary history and inferred a contraction of crinkler-encoding genes in the subclade of Phytophthora containing P. ramorum. There were losses of multiple families and a near complete loss of paralogs in the largest core crinkler family in the ancestor of P. ramorum and sister species P. lateralis. Secreted glycoside hydrolase enzymes showed a similar degree of variation in abundance among genomes of P. ramorum lineages as that observed among several Phytophthora species. We found plasticity among genomes from multiple lineages in a Phytophthora species and provide insights into the evolutionary history of a class of anciently conserved effector genes. [Formula: see text] Copyright © 2025 The Author(s). This is an open access article distributed under the CC BY 4.0 International license.

The GATA family of transcriptional regulators is broadly conserved between plant and animal kingdoms. Here, we report that some of the GATA genes are suppressed in Arabidopsis during fungal and bacterial infections. However, strikingly, GATA21 and GATA22 encode positive regulators of defense against necrotrophic fungal pathogens while acting antagonistically against hemibiotrophic bacterial pathogens. Following infection by Verticillium dahliae, the gata21 and gata22 mutants exhibit defective growth in bolt length and in total silique number. These results suggest that GATA21 and GATA22 regulate growth and reproduction in Arabidopsis both during normal growth and in response to infection by pathogens. Because the GATA family is conserved, our findings have broad implications for the role of GATA transcription regulators in integrating signals from biotic interactions with those for growth and development. [Formula: see text] Copyright © 2025 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Alnus glutinosa, able to establish symbiosis with mutualistic bacteria of the genus Frankia, is one of the main species in European riparian environments, where it performs numerous biological and socioeconomic functions. However, riparian ecosystems face a growing threat from Phytophthora alni, a highly aggressive waterborne pathogen causing severe dieback in A. glutinosa. To date, the tripartite interaction between the host plant, the symbiont Frankia, and the pathogen remains unexplored but is critical for understanding how pathogen-induced stress influences the nodule molecular machinery and thus the host-symbiont metabolism. In the present study, we aimed to explore for the first time how P. alni affects the overall molecular processes of Alnus glutinosa-Frankia nodules, with a special focus on unraveling the spatial expression of defense mechanisms within these tissues. We conducted a laboratory experiment based on P. alni infection of young A. glutinosa seedlings nodulated with Frankia alni ACN14a, noninfected or infected with the pathogen P. alni. Multi-omics analyses (i.e., transcriptomics, proteomics, and metabolomics) were carried out on nodules (N) and associated roots (AR) of the same plant to underline the impact on the nodule molecular processes (i.e., N/AR markers) when the host plant is infected compared with noninfected plants. Our results revealed that P. alni infection modified the molecular nodule processes and induced reprograming of defense-related markers by a shift in associated roots to the detriment of nodules. These findings suggest that A. glutinosa reinforces locally its immune responses in roots but moderates this activation in nodules to preserve its Frankia symbiont. [Formula: see text] Copyright © 2025 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Pathogenic bacteria use Type 3 effector proteins to manipulate host defenses and alter metabolism to favor their survival and spread. The non-model bacterial pathogen Xanthomonas phaseoli pv. manihotis (Xpm) causes devastating disease in cassava. The molecular role of Type 3 effector proteins from Xpm in causing disease is largely unknown. Here, we report that the XopAE effector from Xpm suppresses plant defense responses. Our results show that XopAE is a suppressor of basal defenses such as callose deposition and the production of reactive oxygen species. XopAE targets a small heat shock protein (Mep23-1 cochaperone) in cassava and its homolog Atp23-1 in Arabidopsis. XopAE localizes to the nucleus and in scattered points throughout the cell border, whereas Mep23-1 shows a nucleocytoplasmic localization. Upon interaction, XopAE hijacks Mep23-1 to the scattered points throughout the cell border, and they also interact in the nucleus. Our results indicate that the interaction between XopAE and Mep23-1 is essential for suppressing basal plant defense. This study is one of the first to address the molecular mechanisms deployed by Xpm to cause disease in cassava, a non-model crop plant. [Formula: see text] Copyright © 2025 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

With an increasing demand for renewable fuels, bioenergy crops are being developed with high sugar content and altered cell walls to improve processing efficiency. These traits may have unintended consequences for plant disease resistance. Xanthomonas vasicola pv. holcicola (Xvh), the causal agent of sorghum bacterial leaf streak, is a widespread bacterial pathogen. Here, we show that Xvh expresses several bacterial cell wall degrading enzymes (CWDEs) during sorghum infection, and these are required for full virulence. In tolerant sorghum, Xvh infection results in the induction of a key enzyme in monolignol biosynthesis, Brown midrib12 (Bmr12), but this did not affect lignin content nor composition. Mutation of Bmr12 rendered the tolerant genotype susceptible. Bmr12 encodes caffeic acid O-methyltransferase (COMT), an enzyme that generates sinapaldehyde as its major product. Growth inhibition of Xvh in the presence of sinapaldehyde was observed in vitro. We conclude that mutations that alter the components of the sorghum cell wall can reduce sorghum resistance to Xvh and that Xvh CWDEs contribute to bacterial virulence. Given the enhanced bioprocessing characteristics of bmr12 sorghum, these results provide a cautionary tale for current and future efforts aimed at developing dedicated bioenergy crops. [Formula: see text] Copyright © 2025 The Author(s). This is an open access article distributed under the CC BY 4.0 International license.

Natural plant populations maintain high resistance (R) gene diversities that provide effective pathogen resistance; however, agricultural crops typically contain limited R gene diversity, so resistance is often short-lived, as pathogens evolve rapidly to evade recognition. The Mildew resistance locus A (Mla) R gene family of barley and wheat represents a rich source of natural genetic variation that is ideal for mining disease resistance specificities. Mla R genes encode immune receptor proteins of the nucleotide-binding leucine-rich repeat class that recognize unrelated plant pathogens by binding secreted virulence proteins termed effectors. Using DNA shuffling, we generated a variant library by recombining the barley Mla7 and Mla13 genes in vitro. The variant library was cloned into yeast generating approximately 4,000 independent clones and was screened for interaction with corresponding barley powdery mildew effectors AVR_A13 and AVR_A7 using a yeast two-hybrid assay. This yielded a number of MLA protein variants that interacted with AVR_A13. Sequences of the interacting MLA variants can be clustered into three groups, all of which contain a critical residue from MLA13. Although MLA13 and MLA7 differ by 30 residues across the leucine-rich repeat domain, the replacement of leucine with serine at this position in MLA7 is necessary and sufficient for interaction with AVR_A13 in yeast and AVR_A13-dependent immune signaling in planta. We have established a pipeline that evolves MLAs to recognize distinct pathogen effectors without the requirement for protein structural knowledge and the use of rational design. We suggest that these findings represent a step toward evolving novel recognition capabilities rapidly in vitro. [Formula: see text] Copyright © 2025 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Dwarfing and yellowing are characteristic symptoms caused by viral infections and are considered significant contributors to reduced crop yield. In this study, we identified that infection by barley yellow dwarf virus-GAV (BYDV-GAV) leads to a delay in the flowering process, potentially diminishing grain yield in wheat. The BYDV-GAV movement protein (MP) interacts with vascular plant one-zinc finger proteins (VOZs), which play a crucial role in promoting wheat flowering. Expression of MP inhibits floral transition in Arabidopsis thaliana. Furthermore, BYDV-GAV MP facilitates the degradation of VOZ transcription factors via the 26S proteasome pathway, independently of phytochrome B. Domain B in VOZ is essential for the interaction between VOZ and MP. Our results provide novel insights into the molecular mechanisms underlying virus-induced symptoms. [Formula: see text] Copyright © 2025 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.