Integrated Pangenomic and Systems Biology Analyses Reveal the Genomic Basis of Virulence and Adaptation in Bipolaris sorokiniana

Pangenome Analysis Uncovers Two Pathotypes of Dickeya dadantii, the Causal Agent of Sweetpotato Stem Rot, and Identifies Virulence-Associated Genes.

Bacterial stem and root rot (BSRR), caused by Dickeya dadantii, is a devastating disease affecting sweetpotato [Ipomoea batatas (L.) Lam.] worldwide, yet the pathogen's population structure and core virulence determinants remain poorly understood. Here, we constructed the first comprehensive pangenome of D. dadantii by integrating complete PacBio HiFi sequencing of a representative strain (E36) with resequencing of 32 Chinese isolates and 23 global strains. Population genomic analysis revealed that geographic isolation and host adaptation drive genetic differentiation, with sweetpotato-associated Chinese strains clustering into two major lineages (Groups I and II). Mining the core genome identified 36 conserved candidate effectors, of which CpxP and Spy were experimentally validated as virulence factors: both triggered a hypersensitive response in Nicotiana benthamiana, and their deletion mutants exhibited attenuated virulence on sweetpotato. This study delineates the population architecture of the BSRR pathogen and uncovers key virulence determinants.

Host-driven structuring shapes the landscape of phytoplasma diversity across Indian agroecosystems revealed by multilocus phylogenomics

COMPARATIVE GENOMIC ANALYSIS OF CORE AND ACCESSORY GENES IN RUST FUNGI REVEALS PATHOGENICITY-ASSOCIATED GENE FAMILIES IN Phakopsora pachyrhizi

Accessory genes are thought to contribute to fungal adaptation and pathogenicity by modulating host immunity, while core genes play crucial roles in maintaining fundamental biological processes. Rust fungi (order Pucciniales) are obligate biotrophic plant-pathogens and infect economically relevant crops. Here, we characterize core and accessory gene repertoires across rust fungi, with a particular focus on Phakopsora pachyrhizi, the causal agent of Asian soybean rust. Across Pucciniales genomes, accessory genes represented the largest fraction of gene content (∼44.6% on average), whereas core genes accounted for a smaller proportion (∼18–35%). Notably, variations in accessory gene content among rust fungi are perhaps attributed to lineage-specific gene expansions and losses. Core gene content was positively correlated with total gene number across Pucciniales genomes, suggesting retention after gene duplication events, consistent with their essential biological functions. Among P. pachyrhizi genes expressed during soybean infection, core effectors were associated with cysteine-rich proteins, pectin-degrading enzymes, and SPFH/Band 7 family, while accessory effectors included phosphatidylethanolamine-binding proteins, trehalose phosphatases, and CFEM domain-containing proteins. The in-plant induced core and accessory genes in P. pachyrhizi also comprised multiple families of CAZymes (GH5/GH7 cellulases, CE5 cutinases, CE8 pectinesterases, CE4/GH18 chitin-modifying enzymes); proteases (aspartyl proteases, serine carboxypeptidases, alpha/beta hydrolases); transporters (amino acid permeases, ferric reductase-like transmembrane proteins, and OPT oligopeptide transporter), and transcription factors (bZIP, GATA zinc finger, STE-like, and homeobox KN). Our study highlights that core and accessory gene families have shaped P. pachyrhizi-soybean interactions, identifying promising targets for functional studies aimed at elucidating host-adaptation mechanisms in rust fungi.

Genomic, spatial, and evolutionary insights into a dominant Mycoplasmatota symbiont colonizing the body wall of deep-sea holothurians

Subcuticular bacteria (SCB) are widespread symbionts of echinoderms and often dominate the body-wall microbiome, suggesting important roles in host physiology. However, their diversity, metabolic properties, and host associations remain poorly characterized. Here, we report a novel dominant SCB lineage associated with deep-sea holothurians, Scotoplanes spp. collected from the Northwest Pacific. We recovered two high-quality genomes, including a 649-kb complete circular genome, and propose a new genus and species, “Candidatus Abyssoplasma scotoplanesicola”, within Mycoplasmatota. The two genomes showed a highly reduced metabolic repertoire, lacking central pathways including glycolysis. In contrast, acidic cell-surface-associated proteins, including large proteins exceeding 5,000 amino acids, accounted for 27.6% of the complete genome and clustered near defense islands. Localized genome plasticity in these regions, revealed by comparison between the two closely related genomes, suggests a possible mechanism for diversification of cell-surface proteins at the host-symbiont interface. “Candidatus Abyssoplasma scotoplanesicola” occupied 76.4–98.9% of the body-wall microbiome of the Scotoplanes specimens. Fluorescence in situ hybridization analysis confirmed that these bacteria formed aggregates on the epidermal side of the body wall. Overall, this study provides genome-and spatially resolved views of dominant SCB in holothurians and offers evolutionary insights into host-interface diversification in the deep-sea holothurian body wall.

Lifestyle plasticity and the shared hypocrealean toolkit across Fusarium, Metarhizium, and Trichoderma

SUMMARY Fungi in the genera Fusarium, Metarhizium, and Trichoderma (FMT) are traditionally defined by their roles as plant pathogens, insect pathogens, and mycoparasites, respectively. However, these classifications obscure both their shared hypocrealean ancestry and the remarkable ecological plasticity that characterizes all three genera. Across these lineages, plant endophytism appears to represent the predominant ecological state, with frequent transitions among saprotrophy, symbiosis, pathogenicity, and antagonism. Comparative genomics reveals that FMT fungi possess two-speed genomes comprising conserved core chromosomes and dynamic accessory regions enriched in host-interaction and secondary metabolism genes. These architectures support a shared hypocrealean genomic toolkit that has been differentially modified across lineages. In Fusarium, transitions along the mutualism-to-pathogenicity continuum appear to be driven primarily by regulatory plasticity rather than by major changes in gene content. By contrast, Metarhizium and Trichoderma expanded from ancestral pathogenic states toward broader plant associations through horizontal gene transfer, gene duplication, and diversification of host-recognition, signaling, and metabolite-production pathways. Reproductive strategies similarly reflect ecological divergence. Generalist lineages are predominantly clonal, whereas specialists more frequently retain sexual reproduction, facilitating adaptation to predictable hosts and environments. Ecologically, FMT fungi occupy overlapping but distinct niches: Trichoderma dominates stable environments through mycoparasitism and competitive exclusion; Fusarium thrives in disturbed habitats through rapid colonization of stressed plants; and Metarhizium bridges soil, plant, and insect environments through combined root association and insect pathogenicity. Collectively, FMT fungi illustrate how divergent ecological strategies can emerge through differential modification and regulatory deployment of a shared hypocrealean genomic toolkit.

Whole-genome assemblies and comparative genomics of Fusarium oxysporum f. sp. capsici