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Biocrusts are phototroph-driven communities inhabiting arid soil surfaces. Like plants, most photoautotrophs (largely cyanobacteria) in biocrusts are thought to exchange fixed carbon for essential nutrients like nitrogen with cyanosphere bacteria. Here, we aim to compare beneficial interactions in rhizosphere and cyanosphere environments, including finding growth-promoting strains for hosts from both environments. To examine this, we performed a retrospective analysis of 16S rRNA gene sequencing datasets, host-microbe co-culture experiments between biocrust communities/biocrust isolates and a model grass (Brachypodium distachyon) or a dominant biocrust cyanobacterium (Microcoleus vaginatus), and metabolomic analysis. All 18 microbial phyla in the cyanosphere were also present in the rhizosphere, with additional 17 phyla uniquely found in the rhizosphere. The biocrust microbes promoted the growth of the model grass, and three biocrust isolates (Bosea sp._L1B56, Pseudarthrobacter sp._L1D14 and Pseudarthrobacter picheli_L1D33) significantly promoted the growth of both hosts. Moreover, pantothenic acid was produced by Pseudarthrobacter sp._L1D14 when grown on B. distachyon exudates, and supplementation of plant growth medium with this metabolite increased B. distachyon biomass by over 60%. These findings suggest that cyanobacteria and other diverse photoautotrophic hosts can be a source for new plant growth-promoting microbes and metabolites.

Summary: The onset of stomatal closure reduces transpiration during drought. In seed plants, drought causes declines in plant water status which increases leaf endogenous abscisic acid (ABA) levels required for stomatal closure. There are multiple possible points of increased belowground resistance in the soil–plant atmospheric continuum that could decrease leaf water potential enough to trigger ABA production and the subsequent decreases in transpiration.We investigate the dynamic patterns of leaf ABA levels, plant hydraulic conductance and the point of failure in the soil–plant conductance in the highly embolism‐resistant species Callitris tuberculata using continuous dendrometer measurements of leaf water potential during drought.We show that decreases in transpiration and ABA biosynthesis begin before any permanent decreases in predawn water potential, collapse in soil–plant hydraulic pathway and xylem embolism spread.We find that a dynamic but recoverable increases in hydraulic resistance in the soil in close proximity to the roots is the most likely driver of declines in midday leaf water potential needed for ABA biosynthesis and the onset of decreases in transpiration. [ABSTRACT FROM AUTHOR]

Summary: The rhizosphere microbiome plays critical roles in plant growth and provides promising solutions for sustainable agriculture. While the rhizosphere microbiome frequently fluctuates with the soil environment, recent studies have demonstrated that a small proportion of the microbiome is consistently assembled in the rhizosphere of a specific plant genotype regardless of the soil condition, which is determined by host genetics. Based on these breakthroughs, which involved exploiting the plant‐beneficial function of the rhizosphere microbiome, we propose to divide the rhizosphere microbiome into environment‐dominated and plant genetic‐dominated components based on their different assembly mechanisms. Subsequently, two strategies to explore the different rhizosphere microbiome components for agricultural production are suggested, that is, the precise management of the environment‐dominated rhizosphere microbiome by agronomic practices, and the elucidation of the plant genetic basis of the plant genetic‐dominated rhizosphere microbiome for breeding microbiome‐assisted crop varieties. We finally present the major challenges that need to be overcome to implement strategies for modulating these two components of the rhizosphere microbiome. [ABSTRACT FROM AUTHOR]

Summary: Microbial communities can rapidly respond to stress, meaning plants may encounter altered soil microbial communities in stressful environments. These altered microbial communities may then affect natural selection on plants. Because stress can cause lasting changes to microbial communities, microbes may also cause legacy effects on plant selection that persist even after the stress ceases.To explore how microbial responses to stress and persistent microbial legacy effects of stress affect natural selection, we grew Chamaecrista fasciculata plants in stressful (salt, herbicide, or herbivory) or nonstressful conditions with microbes that had experienced each of these environments in the previous generation.Microbial community responses to stress generally counteracted the effects of stress itself on plant selection, thereby weakening the strength of stress as a selective agent. Microbial legacy effects of stress altered plant selection in nonstressful environments, suggesting that stress‐induced changes to microbes may continue to affect selection after stress is lifted.These results suggest that soil microbes may play a cryptic role in plant adaptation to stress, potentially reducing the strength of stress as a selective agent and altering the evolutionary trajectory of plant populations. [ABSTRACT FROM AUTHOR]

Summary: Legume nodulation requires the detection of flavonoids in the rhizosphere by rhizobia to activate their production of Nod factor countersignals. Here we investigated the flavonoids involved in nodulation of Medicago truncatula.We biochemically characterized five flavonoid‐O‐methyltransferases (OMTs) and a lux‐based nod gene reporter was used to investigate the response of Sinorhizobium medicae NodD1 to various flavonoids.We found that chalcone‐OMT 1 (ChOMT1) and ChOMT3, but not OMT2, 4, and 5, were able to produce 4,4′‐dihydroxy‐2′‐methoxychalcone (DHMC). The bioreporter responded most strongly to DHMC, while isoflavones important for nodulation of soybean (Glycine max) showed no activity. Mutant analysis revealed that loss of ChOMT1 strongly reduced DHMC levels. Furthermore, chomt1 and omt2 showed strongly reduced bioreporter luminescence in their rhizospheres. In addition, loss of both ChOMT1 and ChOMT3 reduced nodulation, and this phenotype was strengthened by the further loss of OMT2.We conclude that: the loss of ChOMT1 greatly reduces root DHMC levels; ChOMT1 or OMT2 are important for nod gene activation in the rhizosphere; and ChOMT1/3 and OMT2 promote nodulation. Our findings suggest a degree of exclusivity in the flavonoids used for nodulation in M. truncatula compared to soybean, supporting a role for flavonoids in rhizobial host range. [ABSTRACT FROM AUTHOR]

Summary: Rhizosphere microbiomes are pivotal for crop fitness, but the principles underlying microbial assembly during root–soil interactions across soils with different nutrient statuses remain elusive.We examined the microbiomes in the rhizosphere and bulk soils of maize plants grown under six long‐term (≥ 29 yr) fertilization experiments in three soil types across middle temperate to subtropical zones.The assembly of rhizosphere microbial communities was primarily driven by deterministic processes. Plant selection interacted with soil types and fertilization regimes to shape the structure and function of rhizosphere microbiomes. Predictive functional profiling showed that, to adapt to nutrient‐deficient conditions, maize recruited more rhizobacteria involved in nutrient availability from bulk soil, although these functions were performed by different species. Metagenomic analyses confirmed that the number of significantly enriched Kyoto Encyclopedia of Genes and Genomes Orthology functional categories in the rhizosphere microbial community was significantly higher without fertilization than with fertilization. Notably, some key genes involved in carbon, nitrogen, and phosphorus cycling and purine metabolism were dominantly enriched in the rhizosphere soil without fertilizer input.In conclusion, our results show that maize selects microbes at the root–soil interface based on microbial functional traits beneficial to its own performance, rather than selecting particular species. [ABSTRACT FROM AUTHOR]

Summary: The link between above‐ and belowground communities is a key uncertainty in drought and rewetting effects on forest carbon (C) cycle.In young beech model ecosystems and mature naturally dry pine forest exposed to 15‐yr‐long irrigation, we performed 13C pulse labeling experiments, one during drought and one 2 wk after rewetting, tracing tree assimilates into rhizosphere communities.The 13C pulses applied in tree crowns reached soil microbial communities of the young and mature forests one and 4 d later, respectively. Drought decreased the transfer of labeled assimilates relative to the irrigation treatment. The 13C label in phospholipid fatty acids (PLFAs) indicated greater drought reduction of assimilate incorporation by fungi (−85%) than by gram‐positive (−43%) and gram‐negative bacteria (−58%).13C label incorporation was more strongly reduced for PLFAs (cell membrane) than for microbial cytoplasm extracted by chloroform. This suggests that fresh rhizodeposits are predominantly used for osmoregulation or storage under drought, at the expense of new cell formation. Two weeks after rewetting, 13C enrichment in PLFAs was greater in previously dry than in continuously moist soils. Drought and rewetting effects were greater in beech systems than in pine forest.Belowground C allocation and rhizosphere communities are highly resilient to drought. [ABSTRACT FROM AUTHOR]

Summary: Biophysicochemical rhizosheath properties play a vital role in plant drought adaptation. However, their integration into the framework of plant drought response is hampered by incomplete mechanistic understanding of their drought responsiveness and unknown linkage to intraspecific plant–soil drought reactions.Thirty‐eight Zea mays varieties were grown under well‐watered and drought conditions to assess the drought responsiveness of rhizosheath properties, such as soil aggregation, rhizosheath mass, net‐rhizodeposition, and soil organic carbon distribution. Additionally, explanatory traits, including functional plant trait adaptations and changes in soil enzyme activities, were measured.Drought restricted soil structure formation in the rhizosheath and shifted plant–carbon from litter‐derived organic matter in macroaggregates to microbially processed compounds in microaggregates. Variety‐specific functional trait modifications determined variations in rhizosheath drought responsiveness. Drought responses of the plant–soil system ranged among varieties from maintaining plant–microbial interactions in the rhizosheath through accumulation of rhizodeposits, to preserving rhizosheath soil structure while increasing soil exploration through enhanced root elongation.Drought‐induced alterations at the root–soil interface may hold crucial implications for ecosystem resilience in a changing climate. Our findings highlight that rhizosheath soil properties are an intrinsic component of plant drought response, emphasizing the need for a holistic concept of plant–soil systems in future research on plant drought adaptation. [ABSTRACT FROM AUTHOR]

The article titled "Corrigendum to Conservation of beneficial microbes between the rhizosphere and the cyanosphere" in the journal New Phytologist acknowledges errors in several figures in a previously published article by Zheng et al. The errors were due to a discrepancy in the R-script used during the revision process, resulting in large error bars in the figures. The corrected figures and their associated legends are provided in the article. The authors apologize for the errors. [Extracted from the article]

Summary: Recent studies on root traits have shown that there are two axes explaining trait variation belowground: the collaboration axis with mycorrhizal partners and the conservation ('fast – slow') axis. However, it is yet unknown whether these trait axes affect the assembly of soilborne fungi. We expect saprotrophic fungi to link to the conservation axis of root traits, whereas pathogenic and arbuscular mycorrhizal fungi link to the collaboration axis, but in opposite directions, as arbuscular mycorrhizal fungi might provide pathogen protection.To test these hypotheses, we sequenced rhizosphere fungal communities and measured root traits in monocultures of 25 grassland plant species, differing in age. Within the fungal guilds, we evaluated fungal species richness, relative abundance and community composition.Contrary to our hypotheses, fungal diversity and relative abundance were not strongly related to the root trait axes. However, saprotrophic fungal community composition was affected by the conservation gradient and pathogenic community composition by the collaboration gradient. The rhizosphere AMF community composition did not change along the collaboration gradient, even though the root trait axis was in line with the root mycorrhizal colonization rate.Overall, our results indicate that in the long term, the root trait axes are linked with fungal community composition. [ABSTRACT FROM AUTHOR]

Summary: The distribution of roots throughout the soil drives depth‐dependent plant–soil interactions and ecosystem processes, particularly in arctic tundra where plant biomass, is predominantly belowground. Vegetation is usually classified from aboveground, but it is unclear whether such classifications are suitable to estimate belowground attributes and their consequences, such as rooting depth distribution and its influence on carbon cycling.We performed a meta‐analysis of 55 published arctic rooting depth profiles, testing for differences both between distributions based on aboveground vegetation types (Graminoid, Wetland, Erect‐shrub, and Prostrate‐shrub tundra) and between 'Root Profile Types' for which we defined three representative and contrasting clusters. We further analyzed potential impacts of these different rooting depth distributions on rhizosphere priming‐induced carbon losses from tundra soils.Rooting depth distribution hardly differed between aboveground vegetation types but varied between Root Profile Types. Accordingly, modelled priming‐induced carbon emissions were similar between aboveground vegetation types when they were applied to the entire tundra, but ranged from 7.2 to 17.6 Pg C cumulative emissions until 2100 between individual Root Profile Types.Variations in rooting depth distribution are important for the circumpolar tundra carbon‐climate feedback but can currently not be inferred adequately from aboveground vegetation type classifications. See also the Commentary on this article by Weber & Iversen, 240: 457–460. [ABSTRACT FROM AUTHOR]

Summary: Root traits including root exudates are key factors affecting plant interactions with soil and thus play an important role in determining ecosystem processes. The drivers of their variation, however, remain poorly understood. We determined the relative importance of phylogeny and species ecology in determining root traits and analyzed the extent to which root exudate composition can be predicted by other root traits.We measured different root morphological and biochemical traits (including exudate profiles) of 65 plant species grown in a controlled system. We tested phylogenetic conservatism in traits and disentangled the individual and overlapping effects of phylogeny and species ecology on traits. We also predicted root exudate composition using other root traits.Phylogenetic signal differed greatly among root traits, with the strongest signal in phenol content in plant tissues. Interspecific variation in root traits was partly explained by species ecology, but phylogeny was more important in most cases. Species exudate composition could be partly predicted by specific root length, root dry matter content, root biomass, and root diameter, but a large part of variation remained unexplained.In conclusion, root exudation cannot be easily predicted based on other root traits and more comparative data on root exudation are needed to understand their diversity. [ABSTRACT FROM AUTHOR]

Summary: Plants impact the development of their rhizosphere microbial communities. It is yet unclear to what extent the root cap and specific root zones contribute to microbial community assembly.To test the roles of root caps and root hairs in the establishment of microbiomes along maize roots (Zea mays), we compared the composition of prokaryote (archaea and bacteria) and protist (Cercozoa and Endomyxa) microbiomes of intact or decapped primary roots of maize inbred line B73 with its isogenic root hairless (rth3) mutant. In addition, we tracked gene expression along the root axis to identify molecular control points for an active microbiome assembly by roots.Absence of root caps had stronger effects on microbiome composition than the absence of root hairs and affected microbial community composition also at older root zones and at higher trophic levels (protists). Specific bacterial and cercozoan taxa correlated with root genes involved in immune response.Our results indicate a central role of root caps in microbiome assembly with ripple‐on effects affecting higher trophic levels and microbiome composition on older root zones. [ABSTRACT FROM AUTHOR]

Summary: Crop rotation can assemble distinct core microbiota as functionally specific barriers against the invasion of banana Fusarium oxysporum pathogens. However, the taxonomic identity of rotation‐unique core taxa and their legacy effects are poorly understood under field conditions.Pepper and eggplant rotations were employed to reveal rotation crop‐ and banana‐unique antagonistic core taxa by in situ tracking of the soil microbiome assembly patterns for 2 yr. The rotation crop‐unique antagonistic taxa were isolated and functionally verified by culture‐dependent techniques, high‐throughput sequencing, and pot experiments.Pepper and eggplant rotations resulted in eight and one rotation‐unique antagonistic core taxa out of 12 507 microbial taxa, respectively. These nine antagonistic taxa were retained the following year and significantly decreased banana wilt disease incidence via legacy effects, although the cultivated strains were exclusively of the genera Bacillus and Pseudomonas. The fermentation broth and volatiles of these two taxa showed strong antagonistic activity, and pot experiments demonstrated high suppression of wilt disease and significant promotion of banana growth.Our study provides a mechanistic understanding of the identification of rotation crop‐unique antagonistic taxa and highlights the importance of targeted cultivation of beneficial microorganisms for optimizing crop rotation‐based scenarios in support of banana agriculture sustainability. [ABSTRACT FROM AUTHOR]

Summary: Root hairs and soil water content are crucial in controlling the release and diffusion of root exudates and shaping profiles of biochemical properties in the rhizosphere. But whether root hairs can offset the negative impacts of drought on microbial activity remains unknown.Soil zymography, 14C imaging and neutron radiography were combined to identify how root hairs and soil moisture affect rhizosphere biochemical properties. To achieve this, we cultivated two maize genotypes (wild‐type and root‐hair‐defective rth3 mutant) under ambient and drought conditions.Root hairs and optimal soil moisture increased hotspot area, rhizosphere extent and kinetic parameters (Vmax and Km) of β‐glucosidase activities. Drought enlarged the rhizosphere extent of root exudates and water content. Colocalization analysis showed that enzymatic hotspots were more colocalized with root exudate hotspots under optimal moisture, whereas they showed higher dependency on water hotspots when soil water and carbon were scarce.We conclude that root hairs are essential in adapting rhizosphere properties under drought to maintain plant nutrition when a continuous mass flow of water transporting nutrients to the root is interrupted. In the rhizosphere, soil water was more important than root exudates for hydrolytic enzyme activities under water and carbon colimitation. See also the Commentary on this article by Zhang et al., 237: 707–709. [ABSTRACT FROM AUTHOR]

Summary: Soil organic carbon (SOC) is a mixture of various carbon (C) compounds with different stability, which can be distinctly affected by the priming effect (PE). However, little is known about how the PE changes with SOC stability.We address this issue by combining results from two experiments and a metaanalysis.We found that the PE increased with the prolongation of soil preincubation, suggesting that higher PE occurred for more stable SOC than for labile SOC. This was further supported by the metaanalysis of 42 observations. There were significant negative relationships between the difference in PE (ΔPE) between labile and more stable SOC and their differences in SOC, microbial biomass C and soil C : N ratio, indicating that soil C availability exerts a vital control on ΔPE.We conclude that, compared with labile SOC, stable SOC can be more vulnerable to priming once microbes are provided with exogenous C substrates. This high vulnerability of stable SOC to priming warrants more attention in future studies on SOC cycling and global change. [ABSTRACT FROM AUTHOR]

Summary: Disentangling the contribution of climatic and edaphic factors to microbiome variation and local adaptation in plants requires an experimental approach to uncouple their effects and test for causality.We used microbial inocula, soil matrices and plant genotypes derived from two natural Arabidopsis thaliana populations in northern and southern Europe in an experiment conducted in climatic chambers mimicking seasonal changes in temperature, day length and light intensity of the home sites of the two genotypes.The southern A. thaliana genotype outperformed the northern genotype in the southern climate chamber, whereas the opposite was true in the northern climate chamber. Recipient soil matrix, but not microbial composition, affected plant fitness, and effects did not differ between genotypes. Differences between chambers significantly affected rhizosphere microbiome assembly, although these effects were small in comparison with the shifts induced by physicochemical differences between soil matrices.The results suggest that differences in seasonal changes in temperature, day length and light intensity between northern and southern Europe have strongly influenced adaptive differentiation between the two A. thaliana populations, whereas effects of differences in soil factors have been weak. By contrast, below‐ground differences in soil characteristics were more important than differences in climate for rhizosphere microbiome differentiation. [ABSTRACT FROM AUTHOR]

The adoption of a holistic approach to root research, that is, one that takes into account all categories of root traits, from anatomy to root morphology, physiology and architecture, as well as interactions with the rhizosphere microbiota, was emphasised as a crucial step in facing the challenges posed by global change. Keywords: Ambassador Program; ISRR11; rhizosphere; root phenotyping; root traits; Rooting2021; roots EN Ambassador Program ISRR11 rhizosphere root phenotyping root traits Rooting2021 roots 2149 2154 6 08/22/22 20220915 NES 220915 Emerging frontiers: root and rhizosphere research in the context of global environmental chan... Natural ecosystems and agricultural production have been threatened by multifaceted global environmental changes. ISRR11, rhizosphere, root traits, Ambassador Program, root phenotyping, Rooting2021, roots Root biology never sleeps: 11th Symposium of the International Society of Root Research (ISRR11) and the 9th International Symposium on Root Development (Rooting2021), 24-28 May 2021. [Extracted from the article]

Summary: Stimulating the development of soil suppressiveness against certain pathogens represents a sustainable solution toward reducing pesticide use in agriculture. However, understanding the dynamics of suppressiveness and the mechanisms leading to pathogen control remain largely elusive.Here, we investigated the mechanisms used by the rhizosphere microbiome induces bacterial wilt disease suppression in a long‐term field experiment where continuous application of bio‐organic fertilizers (BFs) triggered disease suppressiveness when compared to chemical fertilizer application. We further demonstrated in a glasshouse experiment that the suppressiveness of the rhizosphere bacterial communities was triggered mainly by changes in community composition rather than only by the abundance of the introduced biocontrol strain.Metagenomics approaches revealed that members of the families Sphingomonadaceae and Xanthomonadaceae with the ability to produce secondary metabolites were enriched in the BF plant rhizosphere but only upon pathogen invasion. We experimentally validated this observation by inoculating bacterial isolates belonging to the families Sphingomonadaceae and Xanthomonadaceae into conducive soil, which led to a significant reduction in pathogen abundance and increase in nonribosomal peptide synthetase gene abundance.We conclude that priming of the soil microbiome with BF amendment fostered reactive bacterial communities in the rhizosphere of tomato plants in response to biotic disturbance. [ABSTRACT FROM AUTHOR]

Summary: Carbon (C) exuded via roots is proposed to increase under drought and facilitate important ecosystem functions. However, it is unknown how exudate quantities relate to the total C budget of a drought‐stressed tree, that is, how much of net‐C assimilation is allocated to exudation at the tree level.We calculated the proportion of daily C assimilation allocated to root exudation during early summer by collecting root exudates from mature Fagus sylvatica and Picea abies exposed to experimental drought, and combining above‐ and belowground C fluxes with leaf, stem and fine‐root surface area.Exudation from individual roots increased exponentially with decreasing soil moisture, with the highest increase at the wilting point. Despite c. 50% reduced C assimilation under drought, exudation from fine‐root systems was maintained and trees exuded 1.0% (F. sylvatica) to 2.5% (P. abies) of net C into the rhizosphere, increasing the proportion of C allocation to exudates two‐ to three‐fold. Water‐limited P. abies released two‐thirds of its exudate C into the surface soil, whereas in droughted F. sylvatica it was only one‐third.Across the entire root system, droughted trees maintained exudation similar to controls, suggesting drought‐imposed belowground C investment, which could be beneficial for ecosystem resilience. [ABSTRACT FROM AUTHOR]

Summary: Rice diterpenoid phytoalexins (DPs) are secondary metabolites with a well known role in resistance to foliar pathogens. As DPs are also known to be produced and exuded by rice roots, we hypothesised that they might play an important role in plant–nematode interactions, and particularly in defence against phytoparasitic nematodes.We used transcriptome analysis on rice roots to analyse the effect of infection by the root‐knot nematode Meloidogyne graminicola or treatment with resistance‐inducing chemical stimuli on DP biosynthesis genes, and assessed the susceptibility of mutant rice lines impaired in DP biosynthesis to M. graminicola. Moreover, we grew these mutants and their wild‐type in field soil and used metabarcoding to assess the effect of impairment in DP biosynthesis on rhizosphere and root nematode communities.We show that M. graminicola suppresses DP biosynthesis genes early in its invasion process and, conversely, that resistance‐inducing stimuli transiently induce the biosynthesis of DPs. Moreover, we show that loss of DPs increases susceptibility to M. graminicola. Metabarcoding on wild‐type and DP‐deficient plants grown in field soil reveals that DPs significantly alter the composition of rhizosphere and root nematode communities.Diterpenoid phytoalexins are important players in basal and inducible defence against nematode pathogens of rice and help shape rice‐associated nematode communities. [ABSTRACT FROM AUTHOR]

Here, we characterized the independent role of soil microbiomes (bacterial and fungal communities) in determining the flavor chemistry of harvested mustard seed (Brassica juncea). Given the known impacts of soil microbial communities on various plant characteristics, we hypothesized that differences in rhizosphere microbiomes would result in differences in seed flavor chemistry (glucosinolate content). In a glasshouse study, we introduced distinct soil microbial communities to mustard plants growing in an otherwise consistent environment. At the end of the plant life cycle, we characterized the rhizosphere and root microbiomes and harvested produced mustard seeds for chemical characterization. Specifically, we measured the concentrations of glucosinolates, secondary metabolites known to create spicy and bitter flavors. We examined associations between rhizosphere microbial taxa or genes and seed flavor chemistry. We identified links between the rhizosphere microbial community composition and the concentration of the main glucosinolate, allyl, in seeds. We further identified specific rhizosphere taxa predictive of seed allyl concentration and identified bacterial functional genes, namely genes for sulfur metabolism, which could partly explain the observed associations. Together, this work offers insight into the potential influence of the belowground microbiome on the flavor of harvested crops., (© 2024 The Author(s). New Phytologist © 2024 New Phytologist Foundation.)

Intercropping leads to different plant roots directly influencing belowground processes and has gained interest for its promotion of increased crop yields and resource utilization. However, the precise mechanisms through which the interactions between rhizosphere metabolites and the microbiome contribute to plant production remain ambiguous, thus impeding the understanding of the yield-enhancing advantages of intercropping. This study conducted field experiments (initiated in 2013) and pot experiments, coupled with multi-omics analysis, to investigate plant-metabolite-microbiome interactions in the rhizosphere of maize. Field-based data revealed significant differences in metabolite and microbiome profiles between the rhizosphere soils of maize monoculture and intercropping. In particular, intercropping soils exhibited higher microbial diversity and metabolite chemodiversity. The chemodiversity and composition of rhizosphere metabolites were significantly related to the diversity, community composition, and network complexity of soil microbiomes, and this relationship further impacted plant nutrient uptake. Pot-based findings demonstrated that the exogenous application of a metabolic mixture comprising key components enriched by intercropping (soyasapogenol B, 6-hydroxynicotinic acid, lycorine, shikimic acid, and phosphocreatine) significantly enhanced root activity, nutrient content, and biomass of maize in natural soil, but not in sterilized soil. Overall, this study emphasized the significance of rhizosphere metabolite-microbe interactions in enhancing yields in intercropping systems. It can provide new insights into rhizosphere controls within intensive agroecosystems, aiming to enhance crop production and ecosystem services., (© 2024 The Authors. New Phytologist © 2024 New Phytologist Foundation.)

Summary: Climate change‐related soil salinization increases plant stress and decreases productivity. Soil microorganisms are thought to reduce salt stress through multiple mechanisms, so diverse assemblages could improve plant growth under such conditions. Previous studies have shown that microbiome selection can promote desired plant phenotypes, but with high variability. We hypothesized that microbiome selection would be more consistent in saline soils by increasing potential benefits to the plants.In both salt‐amended and untreated soils, we transferred forward Brassica rapa root microbiomes (from high‐biomass or randomly selected pots) across six planting generations while assessing bacterial (16S rRNA) and fungal (ITS) composition in detail. Uniquely, we included an add‐back control (re‐adding initial frozen soil microbiome) as a within‐generation reference for microbiome and plant phenotype selection.We observed inconsistent effects of microbiome selection on plant biomass across generations, but microbial composition consistently diverged from the add‐back control. Although salt amendment strongly impacted microbial composition, it did not increase the predictability of microbiome effects on plant phenotype, but it did increase the rate at which microbiome selection plateaued.These data highlight a disconnect in the trajectories of microbiomes and plant phenotypes during microbiome selection, emphasizing the role of standard controls to explain microbiome selection outcomes. [ABSTRACT FROM AUTHOR]

This article is a Commentary on Zhang et al. (2023), 237: 780–792. [ABSTRACT FROM AUTHOR]

Summary: Roots anchor plants to the soil, providing them with nutrients and water while creating a defence network and facilitating beneficial interactions with a multitude of living organisms and climatological conditions. To facilitate morphological and molecular studies, root research has been conducted using in vitro systems. However, under natural conditions, roots grow in the dark, mainly in the absence of illumination, except for the relatively low illumination of the upper soil surface, and this has been largely ignored. Here, we discuss the results found over the last decade on how experimental exposure of roots to light may bias root development and responses through the alteration of hormonal signalling, cytoskeleton organization, reactive oxygen species or the accumulation of flavonoids, among other factors. Illumination alters the uptake of nutrients or water, and also affects the response of the roots to abiotic stresses and root interactions with the microbiota. Furthermore, we review in vitro systems created to maintain roots in darkness, and provide a comparative analysis of root transcriptomes obtained with these devices. Finally, we identify other experimental variables that should be considered to better mimic soil conditions, whose improvement would benefit studies using in vitro cultivation or enclosed ecosystems. [ABSTRACT FROM AUTHOR]

Summary: The concept of a root economics space (RES) is increasingly adopted to explore root trait variation and belowground resource‐acquisition strategies. Much progress has been made on interactions of root morphology and mycorrhizal symbioses. However, root exudation, with a significant carbon (C) cost (c. 5–21% of total photosynthetically fixed C) to enhance resource acquisition, remains a missing link in this RES. Here, we argue that incorporating root exudation into the structure of RES is key to a holistic understanding of soil nutrient acquisition. We highlight the different functional roles of root exudates in soil phosphorus (P) and nitrogen (N) acquisition. Thereafter, we synthesize emerging evidence that illustrates how root exudation interacts with root morphology and mycorrhizal symbioses at the level of species and individual plant and argue contrasting patterns in species evolved in P‐impoverished vs N‐limited environments. Finally, we propose a new conceptual framework, integrating three groups of root functional traits to better capture the complexity of belowground resource‐acquisition strategies. Such a deeper understanding of the integrated and dynamic interactions of root morphology, root exudation, and mycorrhizal symbioses will provide valuable insights into the mechanisms underlying species coexistence and how to explore belowground interactions for sustainable managed systems. [ABSTRACT FROM AUTHOR]

Desert plants are hypothesized to survive the environmental stress inherent to these regions in part thanks to symbioses with microorganisms, and yet these microbial species, the communities they form, and the forces that influence them are poorly understood. Here we report the first comprehensive investigation of the microbial communities associated with species of Agave, which are native to semiarid and arid regions of Central and North America and are emerging as biofuel feedstocks. We examined prokaryotic and fungal communities in the rhizosphere, phyllosphere, leaf and root endosphere, as well as proximal and distal soil samples from cultivated and native agaves, through Illumina amplicon sequencing. Phylogenetic profiling revealed that the composition of prokaryotic communities was primarily determined by the plant compartment, whereas the composition of fungal communities was mainly influenced by the biogeography of the host species. Cultivated A. tequilana exhibited lower levels of prokaryotic diversity compared with native agaves, although no differences in microbial diversity were found in the endosphere. Agaves shared core prokaryotic and fungal taxa known to promote plant growth and confer tolerance to abiotic stress, which suggests common principles underpinning Agave-microbe interactions.

Summary: Plant–soil feedback (PSF) may influence plant–insect interactions. Although plant defense differs between shoot and root tissues, few studies have examined root‐feeding insect herbivores in a PSF context. We examined here how plant growth and resistance against root‐feeding Delia radicum larvae was influenced by PSF.We conditioned soil with cabbage plants that were infested with herbivores that affect D. radicum through plant‐mediated effects: leaf‐feeding Plutella xylostella caterpillars and Brevicoryne brassicae aphids, root‐feeding D. radicum larvae, and/or added rhizobacterium Pseudomonas simiae WCS417r. We analyzed the rhizosphere microbial community, and in a second set of conspecific plants exposed to conditioned soil, we assessed growth, expression of defense‐related genes, and D. radicum performance.The rhizosphere microbiome differed mainly between shoot and root herbivory treatments. Addition of Pseudomonas simiae did not influence rhizosphere microbiome composition. Plant shoot biomass, gene expression, and plant resistance against D. radicum larvae was affected by PSF in a treatment‐specific manner. Soil conditioning overall reduced plant shoot biomass, Pseudomonas simiae‐amended soil causing the largest growth reduction.In conclusion, shoot and root insect herbivores alter the rhizosphere microbiome differently, with consequences for growth and resistance of plants subsequently exposed to conditioned soil. [ABSTRACT FROM AUTHOR]

Summary: Root traits respond to drought in a species‐specific manner, but little is known about how soil fungal communities and root traits respond to drought in concert.In a glasshouse experiment, we determined the response of soil pathogens, saprotrophs, and mutualistic and all fungi associated with the roots of 24 plant species subjected to drought. At harvest, soil fungal communities were characterized by sequencing. Data on root traits were extracted from a previously published work.Differences in fungal beta diversity between drought and control were plant species specific. For some species, saprotrophic fungi increased in relative abundance and richness with drought, whereas mutualistic fungi showed the opposite pattern. Community structure of pathogenic fungi was plant species specific but was slightly affected by drought.Pathogen composition was correlated with specific root surface area and root : shoot, saprotroph abundance with root tissue density, whereas mutualist composition was correlated with root : shoot. All these were the fungal attributes that best predicted shoot mass.Fungal response to drought depended highly on the fungal group and was related to root trait adjustments to water scarcity. This provides new insights into the role that root trait adjustments to drought may have in modulating plant–fungus interactions in grasslands ecosystems. [ABSTRACT FROM AUTHOR]

Summary: Cable bacteria are sulfide‐oxidising, filamentous bacteria that reduce toxic sulfide levels, suppress methane emissions and drive nutrient and carbon cycling in sediments. Recently, cable bacteria have been found associated with roots of aquatic plants and rice (Oryza sativa). However, the extent to which cable bacteria are associated with aquatic plants in nature remains unexplored.Using newly generated and public 16S rRNA gene sequence datasets combined with fluorescence in situ hybridisation, we investigated the distribution of cable bacteria around the roots of aquatic plants, encompassing seagrass (including seagrass seedlings), rice, freshwater and saltmarsh plants.Diverse cable bacteria were found associated with roots of 16 out of 28 plant species and at 36 out of 55 investigated sites, across four continents. Plant‐associated cable bacteria were confirmed across a variety of ecosystems, including marine coastal environments, estuaries, freshwater streams, isolated pristine lakes and intensive agricultural systems. This pattern indicates that this plant–microbe relationship is globally widespread and neither obligate nor species specific.The occurrence of cable bacteria in plant rhizospheres may be of general importance to vegetation vitality, primary productivity, coastal restoration practices and greenhouse gas balance of rice fields and wetlands. See also the Commentary on this article by Cardini & Malkin, 232: 1897–1900. [ABSTRACT FROM AUTHOR]

Summary: Breeders and evolutionary geneticists have grappled with the complexity of the 'genotype‐to‐phenotype map' for decades. Now, recent studies highlight the relevance of this concept for understanding heritability of plant microbiomes. Because host phenotype is a more proximate cause of microbiome variation than host genotype, microbiome heritability varies across plant anatomy and development. Fine‐scale variation of plant traits within organs suggests that the well‐established concept of 'microbiome compartment' should be refined. Additionally, recent work shows that the balance of deterministic processes (including host genetic effects) vs stochastic processes also varies over time and space. Together, these findings suggest that re‐centering plant phenotype – both as a predictor and a readout of microbiome function – will accelerate new insights into microbiome heritability. [ABSTRACT FROM AUTHOR]

The link between above- and belowground communities is a key uncertainty in drought and rewetting effects on forest carbon (C) cycle. In young beech model ecosystems and mature naturally dry pine forest exposed to 15-yr-long irrigation, we performed 13 C pulse labeling experiments, one during drought and one 2 wk after rewetting, tracing tree assimilates into rhizosphere communities. The 13 C pulses applied in tree crowns reached soil microbial communities of the young and mature forests one and 4 d later, respectively. Drought decreased the transfer of labeled assimilates relative to the irrigation treatment. The 13 C label in phospholipid fatty acids (PLFAs) indicated greater drought reduction of assimilate incorporation by fungi (-85%) than by gram-positive (-43%) and gram-negative bacteria (-58%). 13 C label incorporation was more strongly reduced for PLFAs (cell membrane) than for microbial cytoplasm extracted by chloroform. This suggests that fresh rhizodeposits are predominantly used for osmoregulation or storage under drought, at the expense of new cell formation. Two weeks after rewetting, 13 C enrichment in PLFAs was greater in previously dry than in continuously moist soils. Drought and rewetting effects were greater in beech systems than in pine forest. Belowground C allocation and rhizosphere communities are highly resilient to drought., (© 2024 The Authors. New Phytologist © 2024 New Phytologist Foundation.)

Summary: Approximately 10% of vascular plants are epiphytes and, even though this has long been ignored in past research, are able to interact with a variety of fungi, including mycorrhizal taxa. However, the structure of fungal communities on bark, as well as their relationship with epiphytic plants, is largely unknown.To fill this gap, we conducted environmental metabarcoding of the ITS‐2 region to understand the spatial structure of fungal communities of the bark of tropical trees, with a focus on epiphytic orchid mycorrhizal fungi, and tested the influence of root proximity.For all guilds, including orchid mycorrhizal fungi, fungal communities were more similar when spatially close on bark (i.e. they displayed positive spatial autocorrelation). They also showed distance decay of similarity with respect to epiphytic roots, meaning that their composition on bark increasingly differed, compared to roots, with distance from roots.We first showed that all of the investigated fungal guilds exhibited spatial structure at very small scales. This spatial structure was influenced by the roots of epiphytic plants, suggesting the existence of an epiphytic rhizosphere. Finally, we showed that orchid mycorrhizal fungi were aggregated around them, possibly as a result of reciprocal influence between the mycorrhizal partners. [ABSTRACT FROM AUTHOR]

Summary: It is increasingly evident that the plant microbiome is a strong determinant of plant health. While the ability to manipulate the microbiome in plants and ecosystems recovering from disturbance may be useful, our understanding of the plant microbiome in regenerating plant communities is currently limited.Using 16S ribosomal RNA (rRNA) gene and internal transcribed spacer (ITS) region amplicon sequencing, we characterized the leaf, stem, fine root, rhizome, and rhizosphere microbiome of < 1‐yr‐old aspen saplings and the associated bulk soil after a recent high‐intensity prescribed fire across a burn severity gradient.Consistent with previous studies, we found that soil microbiomes are responsive to fire. We extend these findings by showing that certain plant tissue microbiomes also change in response to fire. Differences in soil microbiome compositions could be attributed to soil chemical characteristics, but, generally, plant tissue microbiomes were not related to plant tissue elemental concentrations. Using source tracking modeling, we also show that fire influences the relative dominance of microbial inoculum and the vertical inheritance of the sapling microbiome from the parent tree.Overall, our results demonstrate how fire impacts plant microbiome assembly, diversity, and composition and highlights potential for further research towards increasing plant fitness and ecosystem recovery after fire events. [ABSTRACT FROM AUTHOR]

Summary: A host‐plant and its associated microbiota depend on one another. However, the assembly process and the functioning of host‐associated microbiota are poorly understood.Herein, rice was used as model plant to investigate the assemblage of bacterial microbiota, including those in the seed, root endosphere and rhizosphere. We also assessed the degree to which endosphere and rhizosphere communities were influenced by vertical transmission through seed and identified the core microbes that potentially associated with plant phenotypic properties.Plant microhabitat, rather than subspecies type, was the major driver shaping plant‐associated bacterial microbiota. Deterministic processes were primarily responsible for community assembly in all microhabitats. The influence of vertical transmission from seed to root‐associated bacterial communities appeared to be quite weak (endosphere) or even absent (rhizosphere). A core microbial community composed of 15 generalist species persisted across different microhabitats and represented key connectors in networks. Host‐plant functional traits were linked to the relative abundance of these generalist core microbes and could be predicted from them using machine learning algorithms.Overall, bacterial microbiota is assembled by host‐plant interactions in a deterministic‐based manner. This study enhances our understanding of the driving mechanisms and associations of microbiota in various plant microhabitats and provides new perspectives to improve plant performance. [ABSTRACT FROM AUTHOR]

(b) Global change factors alter plant microbiota assemblages and modulate beneficial plant-microbe interactions. Keywords: global change; microbiome; microbiota; phyllosphere; plant-microbe interactions; rhizosphere; supra-organisms; sustainable terrestrial ecosystems EN global change microbiome microbiota phyllosphere plant-microbe interactions rhizosphere supra-organisms sustainable terrestrial ecosystems 1907 1909 3 05/25/22 20220615 NES 220615 Plant-associated microorganisms may be invisible to the naked eye, yet they play a key role in the future sustainability of terrestrial ecosystems - from arable lands to rainforests, through tundra and taiga to deserts. Global change, microbiome, microbiota, phyllosphere, plant-microbe interactions, rhizosphere, supra-organisms, sustainable terrestrial ecosystems Defining the components, dynamics, functions and interactions of the core plant-associated microbiota will assist in developing microbiome-based solutions to create healthy, resilient and sustainable plant ecosystems. [Extracted from the article]

The rhizosphere priming effect (RPE) is a mechanism by which plants interact with soil functions. The large impact of the RPE on soil organic matter decomposition rates (from 50% reduction to 380% increase) warrants similar attention to that being paid to climatic controls on ecosystem functions. Furthermore, global increases in atmospheric CO2 concentration and surface temperature can significantly alter the RPE. Our analysis using a game theoretic model suggests that the RPE may have resulted from an evolutionarily stable mutualistic association between plants and rhizosphere microbes. Through model simulations based on microbial physiology, we demonstrate that a shift in microbial metabolic response to different substrate inputs from plants is a plausible mechanism leading to positive or negative RPEs. In a case study of the Duke Free-Air CO2 Enrichment experiment, performance of the PhotoCent model was significantly improved by including an RPE-induced 40% increase in soil organic matter decomposition rate for the elevated CO2 treatment--demonstrating the value of incorporating the RPE into future ecosystem models. Overall, the RPE is emerging as a crucial mechanism in terrestrial ecosystems, which awaits substantial research and model development.

Summary: In Arabidopsis thaliana, PROPEPs and their derived elicitor‐active Pep epitopes provide damage‐associated molecular patterns (DAMPs), which trigger defence responses through cell‐surface receptors PEPR1 and PEPR2. In addition, Pep peptides induce root growth inhibition and root hair formation, however their relationships and coordinating mechanisms are poorly understood.Here, we reveal that Pep1‐mediated root hair formation requires PEPR‐associated kinases BAK1/BKK1 and BIK1/PBL1, ethylene, auxin and root hair differentiation regulators, in addition to PEPR2.Our analysis on 69 accessions unravels intraspecies variations in Pep1‐induced root hair formation and growth inhibition. The absence of a positive correlation between the two traits suggests their separate regulation and diversification in natural populations of A. thaliana.Restricted PEPR2 expression to certain root tissues is sufficient to induce root hair formation and growth inhibition in response to Pep1, indicating the capacity of non‐cell‐autonomous receptor signalling in different root tissues. Of particular note, root hair cell‐specific PEPR2 expression uncouples defence activation from root growth inhibition and root hair formation, suggesting a unique property of root hairs in root defence activation following Pep1 recognition. [ABSTRACT FROM AUTHOR]

Summary: An emerging experimental framework suggests that plants under biotic stress may actively seek help from soil microbes, but empirical evidence underlying such a 'cry for help' strategy is limited.We used integrated microbial community profiling, pathogen and plant transcriptive gene quantification and culture‐based methods to systematically investigate a three‐way interaction between the wheat plant, wheat‐associated microbiomes and Fusarium pseudograminearum (Fp).A clear enrichment of a dominant bacterium, Stenotrophomonas rhizophila (SR80), was observed in both the rhizosphere and root endosphere of Fp‐infected wheat. SR80 reached 3.7 × 107 cells g−1 in the rhizosphere and accounted for up to 11.4% of the microbes in the root endosphere. Its abundance had a positive linear correlation with the pathogen load at base stems and expression of multiple defence genes in top leaves. Upon re‐introduction in soils, SR80 enhanced plant growth, both the below‐ground and above‐ground, and induced strong disease resistance by boosting plant defence in the above‐ground plant parts, but only when the pathogen was present.Together, the bacterium SR80 seems to have acted as an early warning system for plant defence. This work provides novel evidence for the potential protection of plants against pathogens by an enriched beneficial microbe via modulation of the plant immune system. [ABSTRACT FROM AUTHOR]

Summary: Since the holobiont concept came into the limelight ten years ago, we have become aware that responses of holobionts to climate change stressors may be driven by shifts in the microbiota. However, the complex interactions underlying holobiont responses across aquatic and terrestrial ecosystems remain largely unresolved. One of the key factors driving these responses is the infochemical‐mediated communication in the holobiont. In order to come up with a holistic picture, in this Viewpoint we compare mechanisms and infochemicals in the rhizosphere of plants and the eco‐chemosphere of seaweeds in response to climate change stressors and other environmental stressors, including drought, warming and nutrient stress. Furthermore, we discuss the inclusion of chemical ecology concepts that are of crucial importance in driving holobiont survival, adaptation and/or holobiont breakdown. Infochemicals can thus be regarded as a 'missing link' in our understanding of holobiont response to climate change and should be investigated while investigating the responses of plant and seaweed holobionts to climate change. This will set the basis for improving our understanding of holobiont responses to climate change stressors across terrestrial and aquatic ecosystems. [ABSTRACT FROM AUTHOR]

Summary: Fine roots, and their functional traits, influence associated rhizosphere microorganisms via root exudation and root litter quality. However, little information is known about their relationship with rhizosphere microbial taxa and functional guilds.We investigated the relationships of 11 fine root traits of 20 sub‐arctic tundra meadow plant species and soil microbial community composition, using phospholipid fatty acids (PLFAs) and high‐throughput sequencing. We primarily focused on the root economics spectrum, as it provides a useful framework to examine plant strategies by integrating the co‐ordination of belowground root traits along a resource acquisition–conservation trade‐off axis.We found that the chemical axis of the fine root economics spectrum was positively related to fungal to bacterial ratios, but negatively to Gram‐positive to Gram‐negative bacterial ratios. However, this spectrum was unrelated to the relative abundance of functional guilds of soil fungi. Nevertheless, the relative abundance of arbuscular mycorrhizal fungi was positively correlated to root carbon content, but negatively to the numbers of root forks per root length.Our results suggest that the fine root economics spectrum is important for predicting broader groups of soil microorganisms (i.e. fungi and bacteria), while individual root traits may be more important for predicting soil microbial taxa and functional guilds. [ABSTRACT FROM AUTHOR]

Summary: While it is known that interactions between plants and soil fungi drive many essential ecosystem functions, considerable uncertainty exists over the drivers of fungal community composition in the rhizosphere. Here, we examined the roles of plant species identity, phylogeny and functional traits in shaping rhizosphere fungal communities and tested the robustness of these relationships to environmental change.We conducted a glasshouse experiment consisting of 21 temperate grassland species grown under three different environmental treatments and characterised the fungal communities within the rhizosphere of these plants.We found that plant species identity, plant phylogenetic relatedness and plant traits all affected rhizosphere fungal community composition. Trait relationships with fungal communities were primarily driven by interactions with arbuscular mycorrhizal fungi, and root traits were stronger predictors of fungal communities than leaf traits. These patterns were independent of the environmental treatments the plants were grown under.Our results showcase the key role of plant root traits, especially root diameter, root nitrogen and specific root length, in driving rhizosphere fungal community composition, demonstrating the potential for root traits to be used within predictive frameworks of plant–fungal relationships. Furthermore, we highlight how key limitations in our understanding of fungal function may obscure previously unmeasured plant–fungal interactions. [ABSTRACT FROM AUTHOR]

Recent advances in the partitioning of autotrophic from heterotrophic respiration processes in soils in conjunction with new high temporal resolution soil respiration data sets offer insights into biotic and environmental controls of respiration. Besides temperature, many emerging controlling factors have not yet been incorporated into ecosystem-scale models. We synthesize recent research that has partitioned soil respiration into its process components to evaluate effects of nitrogen, temperature and photosynthesis on autotrophic flux from soils at the ecosystem level. Despite the widely used temperature dependence of root respiration, gross primary productivity (GPP) can explain most patterns of ecosystem root respiration (and to some extent heterotrophic respiration) at within-season time-scales. Specifically, heterotrophi crespiration is influenced by a seasonally variable supply of recent photosynthetic products in the rhizosphere. The contribution of stored root carbon (C) to root respiratory fluxes also varied seasonally, partially decoupling the proportion of photosynthetic C driving root respiration. In order to reflect recent insights, new hierarchical models, which incorporate root respiration as a primary function of GPP and which respond to environmental variables by modifying Callocation belowground, are needed for better prediction of future ecosystem C sequestration.

Endoplasmic reticulum (ER) bodies are ER-derived structures that contain a large amount of PYK10 myrosinase, which hydrolyzes tryptophan (Trp)-derived indole glucosinolates (IGs). Given the well-described role of IGs in root-microbe interactions, we hypothesized that ER bodies in roots are important for interaction with soil-borne microbes at the root-soil interface. We used mutants impaired in ER bodies (nai1), ER body-resident myrosinases (pyk10bglu21), IG biosynthesis (myb34/51/122), and Trp specialized metabolism (cyp79b2b3) to profile their root microbiota community in natural soil, evaluate the impact of axenically collected root exudates on soil or synthetic microbial communities, and test their response to fungal endophytes in a mono-association setup. Tested mutants exhibited altered bacterial and fungal communities in rhizoplane and endosphere, respectively. Natural soils and bacterial synthetic communities treated with mutant root exudates exhibited distinctive microbial profiles from those treated with wild-type (WT) exudates. Most tested endophytes severely restricted the growth of cyp79b2b3, a part of which also impaired the growth of pyk10bglu21. Our results suggest that root ER bodies and their resident myrosinases modulate the profile of root-secreted metabolites and thereby influence root-microbiota interactions., (© 2023 The Authors New Phytologist © 2023 New Phytologist Foundation.)

Summary: Understanding how plant species influence soil nutrient cycling is a major theme in terrestrial ecosystem ecology. However, the prevailing paradigm has mostly focused on litter decomposition, while rhizosphere effects on soil organic matter (SOM) decomposition have attracted little attention.Using a dual 13C/15N labeling approach in a 'common garden' glasshouse experiment, we investigated how the economic strategies of 12 grassland plant species (graminoids, forbs and legumes) drive soil nitrogen (N) cycling via rhizosphere processes, and how this in turn affects plant N acquisition and growth.Acquisitive species with higher photosynthesis, carbon rhizodeposition and N uptake than conservative species induced a stronger acceleration of soil N cycling through rhizosphere priming of SOM decomposition. This allowed them to take up larger amounts of N and allocate it above ground to promote photosynthesis, thereby sustaining their faster growth. The N2‐fixation ability of legumes enhanced rhizosphere priming by promoting photosynthesis and rhizodeposition.Our study demonstrates that the economic strategies of plant species regulate a plant–soil carbon–nitrogen feedback operating through the rhizosphere. These findings provide novel mechanistic insights into how plant species with contrasting economic strategies sustain their nutrition and growth through regulating the cycling of nutrients by soil microbes in their rhizosphere. [ABSTRACT FROM AUTHOR]

Summary: Macroorganisms' genotypes shape their phenotypes, which in turn shape the habitat available to potential microbial symbionts. This influence of host genotype on microbiome composition has been demonstrated in many systems; however, most previous studies have either compared unrelated genotypes or delved into molecular mechanisms. As a result, it is currently unclear whether the heritability of host‐associated microbiomes follows similar patterns to the heritability of other complex traits.We take a new approach to this question by comparing the microbiomes of diverse maize inbred lines and their F1 hybrid offspring, which we quantified in both rhizosphere and leaves of field‐grown plants using 16S‐v4 and ITS1 amplicon sequencing.We show that inbred lines and hybrids differ consistently in the composition of bacterial and fungal rhizosphere communities, as well as leaf‐associated fungal communities. A wide range of microbiome features display heterosis within individual crosses, consistent with patterns for nonmicrobial maize phenotypes. For leaf microbiomes, these results were supported by the observation that broad‐sense heritability in hybrids was substantially higher than narrow‐sense heritability.Our results support our hypothesis that at least some heterotic host traits affect microbiome composition in maize. [ABSTRACT FROM AUTHOR]