New Phytologist最新文献

Autonomously self-fertilizing plants possess disproportionate abilities to found populations. Viewed from the metapopulation perspective, founding events should be frequent in such plants, but the intensity and timing of bottlenecks and recovery should vary among populations. We tested the hypothesis that variation in these demographic characteristics in one such species helps to explain variation in levels of genetic diversity and population genomic signatures of inbreeding, relative recombination, and microscale spatial genetic structure. We used reduced-representation sequence data from 11 populations of the dimorphic cleistogamous (CL) species Impatiens capensis, a species that has figured prominently in evolutionary studies. The populations occur in a landscape where suitable habitat is fragmented. Population genomic analyses revealed significant among-population variation in demographic history, genetic diversity, inbreeding, relative recombination, tracts of homozygosity by descent, and spatial autocorrelation of genotypes at microgeographic scale Our findings support the hypothesis that variation in the intensity of bottlenecks and length of the postbottleneck recovery phase in autonomously self-fertilizing plants leads to variation in genetic diversity and a suite of associated population genomic signatures of inbreeding. We suggest that these findings have consequences for understanding evolutionary processes and guiding conservation strategies in fragmented habitats for dimorphic CL species.

Plant immunity is complex, and studies of leaf epidermal cells attacked by powdery mildew fungi have been instrumental in revealing how it relies on plant endomembrane trafficking. Immunity against these biotrophic fungi is manifested as cell wall deposits ('papillae') and the hypersensitive reaction (HR), both involving plant endomembrane traffic. Papillae contain extracellular vesicles (EVs), some of which depend on the 'endosomal sorting complexes required for transport' machinery, while others depend on mechanisms yet to be uncovered. Existence of two such EV pathways agrees with several old electron microscopy observations of papillae. Interestingly, resistance protein-activated HR has been shown to be a form of immunity also depending on membrane trafficking, namely the pathway to the vacuole.

Beneficial rhizobacteria and viral pathogens can both alter host plant phenotypes, yet little is known about how their simultaneous presence influences plant metabolism and species interactions. We investigated how two rhizobacteria, Bradyrhizobium japonicum and Delftia acidovorans, together with bean pod mottle virus (BPMV), shape soybean metabolism and interactions with the BPMV vector Epilachna varivestis. Using a multifactorial experimental design, we combined metabolomics, transcriptomics, and pathway analyses with behavioral assays to assess the impacts of rhizobacteria inoculation and BPMV infection on soybean physiology and E. varivestis feeding preferences. Beetle adults preferred feeding on rhizobia-inoculated and virus-infected plants, and larvae gained more weight on these hosts. Rhizobacteria inoculation and BPMV infection both increased primary metabolites (e.g. beta-alanine, myo-inositol, amino acids, and organic acids) while reducing secondary metabolites (e.g. kaempferol, rutin, and other flavonoids). Transcriptome analyses revealed shifts in defense- and metabolism-related pathways, particularly under combined treatments. Our findings demonstrate that mutualistic and pathogenic symbionts reshape soybean metabolism in unique ways when they cocolonize the same host. These changes can alter symbiont fitness, as well as vector feeding behavior and performance in ways that enhance pathogen transmission.

Arbuscular mycorrhizal fungi (AMF) are widespread plant symbionts that enhance nutrient acquisition and influence ecosystem productivity. Previous chromosome-level assemblies of the model species Rhizophagus irregularis revealed a two-compartment genome architecture (active A and repressed B chromatin compartments), yet its conservation across evolutionarily distant AMF lineages remains unresolved. Here, we present a chromosome-scale and 3D genome assembly of Gigaspora margarita isolate BEG34 - the largest and most repeat-rich AMF genome to date - alongside that of its obligate endobacterium, Candidatus Glomerobacter gigasporarum (CaGg), using PacBio HiFi and Hi-C sequencing. The G. margarita genome comprises 43 chromosomes (792 Mb) organized into A/B compartments and Topologically Associating Domains, structures that are conserved across two AMF orders and remain stable irrespective of the presence of endobacteria in germinating spores. We uncover 21 divergent rDNA operons distributed across six chromosomes and show that these physically interact, suggesting conserved nucleolar organization. We also reveal that the CaGg genome is tripartite and mobilome-rich, encoding prophages, an orphan CRISPR array, and complete pathways for many novel and essential cofactors, including heme, which may enhance host bioenergetics. We also find that the endobacterium's presence modulates transposable elements expression in G. margarita. These findings reveal conserved principles of chromatin architecture in AMF symbionts and highlight the tight molecular interplay between fungal hosts and their endosymbionts, offering new insights into genome evolution and symbiotic adaptation.

Plants modulate their surrounding microbiome via root exudates and such conditioned soil microbiomes feed back on the performance of the next generation of plants. How plants perceive altered soil microbiomes and modulate their performance in response to such microbiome feedbacks, however, remains largely unknown. As tool to condition contrasting microbiomes in soil, we made use of two maize lines, which differ in their ability to exude benzoxazinoids (BXs). Based on these differentially conditioned soil microbiomes we have established a model system with Arabidopsis thaliana (Arabidopsis) to investigate the mechanisms of microbiome feedbacks. Arabidopsis plants responding to the BX-conditioned soil microbiome grew better and were developmentally more advanced. Further, these plants harboured differential root bacterial communities, showed enhanced defence signatures in transcriptomes of their shoots, and they were more resistant to the fungal pathogen Botrytis cinerea. Intriguingly, Arabidopsis responded with both improved growth and enhanced defence to the BX-conditioned soil microbiome, and we found that this simultaneous increase of growth and defence was mediated by priming of the defences. Further advancing our basic understanding of how plants respond to soil microbiomes and mediate their feedbacks is particularly important for the goal to improve crops so they can benefit from their soil microbiome.

Tropical peatlands are critical for climate mitigation due to their dual role as major carbon sinks and methane sources. In rainforests, high and stable rainfall supports peat accumulation in tropical climates. However, groundwater-fed peatlands in seasonally dry tropical ecosystems remain poorly understood, despite their potential importance in global carbon dynamics. Here, we present an integrated carbon assessment in organic soil ecosystems (locally known as Veredas and Campos úmidos) in the Brazilian savanna. We quantified carbon in soil and biomass, dated carbon using radiocarbon, and evaluated chemical stability using infrared spectrometry. We used machine learning models to map their potential area. Additionally, we measured soil CO₂ and CH₄ efluxes to evaluate the influence of climatic seasonality on emissions. Veredas contained exceptionally high carbon stocks (c. 1200 Mg C ha^-1) accumulated over c. 20 000 yr and spanning c. 16.7 Mha. However, spectroscopy indicated low carbon stability compared to other tropical peatlands, and c. 70% of annual CO₂ and CH₄ emissions occurred during the dry season. Our findings show that the Brazilian Cerrado harbors one of the largest carbon-storing ecosystems in the tropical Americas, yet one that is highly vulnerable to land-use change and intensified drought. Despite their wide distribution, peat accumulation and the extent of Veredas remain uncertain.

Bioregionalisation is a hierarchical system that categorises geographical areas according to their biotic composition and evolutionary history. While a global bioregionalisation has been proposed for angiosperms, this is lacking for plant families with global relevance, such as orchids. We used 732 359 orchid distribution records and a phylogeny of 19 123 species to define the global bioregionalisation of orchids based on phylogenetic beta diversity at 200 × 200 km resolution. Using the resulting bioregionalisation, we analysed the environmental drivers that determine the formation of realms. Additionally, we assessed the effect of sampling completeness, different metrics, and spatial resolutions. We identified six global orchid realms (Australian, Andean-Patagonian, Neotropical, Afrotropical, Indo-Malaysian, and Holarctic) and 10 bioregions; four main transition zones were also detected. Mean annual precipitation and temperature, and precipitation and temperature seasonality, had the strongest influence on the delimitation of realms. We present a global bioregionalisation for orchids, identifying the environmental factors that determine the realms. More generally, these results highlight the importance of bioregionalisation for understanding evolutionary patterns of taxonomic families. Using a comprehensive seven-step methodology, we emphasize the need to account for sampling completeness and spatial resolution in such analyses.