Flavonoid-attracted Aeromonas sp. from the Arabidopsis root microbiome enhances plant dehydration resistance

Barnes E.M., Tringe S.G.

Plants benefit from their close association with soil microbes which assist in their response to abiotic and biotic stressors. Yet much of what we know about plant stress responses is based on studies where the microbial partners were uncontrolled and unknown. Under climate change, the soil microbial community will also be sensitive to and respond to abiotic and biotic stressors. Thus, facilitating plant adaptation to climate change will require a systems-based approach that accounts for the multi-dimensional nature of plant–microbe–environment interactions. In this perspective, we highlight some of the key factors influencing plant–microbe interactions under stress as well as new tools to facilitate the controlled study of their molecular complexity, such as fabricated ecosystems and synthetic communities. When paired with genomic and biochemical methods, these tools provide researchers with more precision, reproducibility, and manipulability for exploring plant–microbe–environment interactions under a changing climate.

Singh S.K., Wu X., Shao C., Zhang H.

Nutrient availability is a determining factor for crop yield and quality. While fertilization is a major approach for improving plant nutrition, its efficacy can be limited and the production and application of fertilizers frequently bring problems to the environment. A large number of soil microbes are capable of enhancing plant nutrient acquisition and thereby offer environmentally benign solutions to meet the requirements of plant nutrition. Herein we provide summations of how beneficial microbes enhance plant acquisition of macronutrients and micronutrients. We also review recent studies on nutrition-dependent plant-microbe interactions, which highlight the plant’s initiative in establishing or deterring the plant-microbe association. By dissecting complex signaling interactions between microbes within the root microbiome, a greater understanding of microbe-enhanced plant nutrition under specific biotic and abiotic stresses will be possible.

Fan L., Yao H., Deng S., Jia F., Cai W., Hu Z., Guo J., Li H.

A step-feed anoxic/oxic/anoxic/oxic (SF-A/O/A/O) was developed and successfully applied to full-scale coking wastewater treatment. The performance and microbial community were evaluated and systematically compared with the anoxic/oxic/oxic (A/O/O) process. SF-A/OA/O process exhibited efficient removal of COD, NH 4 + -N, TN, phenols, and cyanide with corresponding average effluent concentrations of 317.9, 1.8, 46.2, 1.1, and 0.2 mg·L −1 , respectively. In particular, the TN removal efficiency of A/O/O process was only 7.8%, with an effluent concentration of 300.6 mg·L −1 . Furthermore, polycyclic aromatic hydrocarbons with high molecular weight were the dominant compounds in raw coking wastewater, which were degraded to a greater extent in SF-A/OA/O. The abundance in Thiobacillus , SM1A02 , and Thauera could be the main reason why SF-A/O/A/O was superior to A/O/O in treating TN. The microbial community structure of SF-A/O/A/O was similar among stages in system (P ≥ 0.05, Welch's t -test) and was less affected by environmental factors, which may have been one of the important factors in the system's strong stability. • SF-A/O/A/O process was successfully applied at full-scale to treat coking wastewater. • Comparing SF-A/O/A/O with A/O/O process on the performance and microbial community. • SF-A/O/A/O process was able to reduce TN by 85.8%, while the A/O/O was only 7.8%. • High molecular weight PAHs were degraded to a greater extent in SF-A/OA/O. • Similar of microbial community may make contribution to the stability of SF-A/O/A/O.

Zhang H., Zhu J., Gong Z., Zhu J.

Plants cannot move, so they must endure abiotic stresses such as drought, salinity and extreme temperatures. These stressors greatly limit the distribution of plants, alter their growth and development, and reduce crop productivity. Recent progress in our understanding of the molecular mechanisms underlying the responses of plants to abiotic stresses emphasizes their multilevel nature; multiple processes are involved, including sensing, signalling, transcription, transcript processing, translation and post-translational protein modifications. This improved knowledge can be used to boost crop productivity and agricultural sustainability through genetic, chemical and microbial approaches. In this Review, Zhang et al. summarize our current understanding of the molecular mechanisms underlying the responses of plants to abiotic stresses, and how this knowledge can be used to improve crop resilience through genetic, chemical and microbial approaches.

Morcillo R., Vílchez J., Zhang S., Kaushal R., He D., Zi H., Liu R., Niehaus K., Handa A., Zhang H.

Water deficit is one of the major constraints to crop production and food security worldwide. Some plant growth-promoting rhizobacteria (PGPR) strains are capable of increasing plant drought resistance. Knowledge about the mechanisms underlying bacteria-induced plant drought resistance is important for PGPR applications in agriculture. In this study, we show the drought stress-mitigating effects on tomato plants by the Bacillus megaterium strain TG1-E1, followed by the profiling of plant transcriptomic responses to TG1-E1 and the profiling of bacterial extracellular metabolites. Comparison between the transcriptomes of drought-stressed plants with and without TG1-E1 inoculation revealed bacteria-induced transcriptome reprograming, with highlights on differentially expressed genes belonging to the functional categories including transcription factors, signal transduction, and cell wall biogenesis and organization. Mass spectrometry-based analysis identified over 40 bacterial extracellular metabolites, including several important regulators or osmoprotectant precursors for increasing plant drought resistance. These results demonstrate the importance of plant transcriptional regulation and bacterial metabolites in PGPR-induced plant drought resistance.

Yu P., He X., Baer M., Beirinckx S., Tian T., Moya Y.A., Zhang X., Deichmann M., Frey F.P., Bresgen V., Li C., Razavi B.S., Schaaf G., von Wirén N., Su Z., et. al.

Beneficial interactions between plant roots and rhizosphere microorganisms are pivotal for plant fitness. Nevertheless, the molecular mechanisms controlling the feedback between root architecture and microbial community structure remain elusive in maize. Here, we demonstrate that transcriptomic gradients along the longitudinal root axis associate with specific shifts in rhizosphere microbial diversity. Moreover, we have established that root-derived flavones predominantly promote the enrichment of bacteria of the taxa Oxalobacteraceae in the rhizosphere, which in turn promote maize growth and nitrogen acquisition. Genetic experiments demonstrate that LRT1-mediated lateral root development coordinates the interactions of the root system with flavone-dependent Oxalobacteraceae under nitrogen deprivation. In summary, these experiments reveal the genetic basis of the reciprocal interactions between root architecture and the composition and diversity of specific microbial taxa in the rhizosphere resulting in improved plant performance. These findings may open new avenues towards the breeding of high-yielding and nutrient-efficient crops by exploiting their interaction with beneficial soil microorganisms. The link between rhizosphere microbial community, root architecture and performance in nitrogen-poor soils is comprehensively investigated in maize, and the role of exuded flavone to promote specific beneficial bacterial taxa is characterized.

Li N., Bo C., Zhang Y., Wang L.

Abstract Leaf senescence can be triggered by multiple abiotic stresses including darkness, nutrient limitation, salinity, and drought. Recently, heatwaves have been occurring more frequently, and they dramatically affect plant growth and development. However, the underlying molecular networks of heat stress-induced leaf senescence remain largely uncharacterized. Here we showed that PHYTOCHROME INTERACTING FACTOR 4 (PIF4) and PIF5 proteins could efficiently promote heat stress-induced leaf senescence in Arabidopsis. Transcriptomic profiling analysis revealed that PIF4 and PIF5 are likely to function through multiple biological processes including hormone signaling pathways. Further, we characterized NAC019, SAG113, and IAA29 as direct transcriptional targets of PIF4 and PIF5. The transcription of NAC019, SAG113, and IAA29 changes significantly in daytime after heat treatment. In addition, we demonstrated that PIF4 and PIF5 proteins were accumulated during the recovery after heat treatment. Moreover, we showed that heat stress-induced leaf senescence is gated by the circadian clock, and plants might be more actively responsive to heat stress-induced senescence during the day. Taken together, our findings proposed important roles for PIF4 and PIF5 in mediating heat stress-induced leaf senescence, which may help to fully illustrate the molecular network of heat stress-induced leaf senescence in higher plants and facilitate the generation of heat stress-tolerant crops.

Kaushal R., Peng L., Singh S.K., Zhang M., Zhang X., Vílchez J.I., Wang Z., He D., Yang Y., Lv S., Xu Z., Morcillo R.J., Wang W., Huang W., Paré P.W., et. al.

Plants are naturally associated with root microbiota, which are microbial communities influential to host fitness. Thus, it is important to understand how plants control root microbiota. Epigenetic factors regulate the readouts of genetic information and consequently many essential biological processes. However, it has been elusive whether RNA-directed DNA methylation (RdDM) affects root microbiota assembly. By applying 16S rRNA gene sequencing, we investigated root microbiota of Arabidopsis mutants defective in the canonical RdDM pathway, including dcl234 that harbors triple mutation in the Dicer-like proteins DCL3, DCL2, and DCL4, which produce small RNAs for RdDM. Alpha diversity analysis showed reductions in microbe richness from the soil to roots, reflecting the selectivity of plants on root-associated bacteria. The dcl234 triple mutation significantly decreases the levels of Aeromonadaceae and Pseudomonadaceae, while it increases the abundance of many other bacteria families in the root microbiota. However, mutants of the other examined key players in the canonical RdDM pathway showed similar microbiota as Col-0, indicating that the DCL proteins affect root microbiota in an RdDM-independent manner. Subsequently gene analysis by shotgun sequencing of root microbiome indicated a selective pressure on microbial resistance to plant defense in the dcl234 mutant. Consistent with the altered plant-microbe interactions, dcl234 displayed altered characters, including the mRNA and sRNA transcriptomes that jointly highlighted altered cell wall organization and up-regulated defense, the decreased cellulose and callose deposition in root xylem, and the restructured profile of root exudates that supported the alterations in gene expression and cell wall modifications. Our findings demonstrate an important role of the DCL proteins in influencing root microbiota through integrated regulation of plant defense, cell wall compositions, and root exudates. Our results also demonstrate that the canonical RdDM is dispensable for Arabidopsis root microbiota. These findings not only establish a connection between root microbiota and plant epigenetic factors but also highlight the complexity of plant regulation of root microbiota.

Dong N., Lin H.

Phenylpropanoid metabolism is one of the most important metabolisms in plants, yielding more than 8,000 metabolites contributing to plant development and plant-environment interplay. Phenylpropanoid metabolism materialized during the evolution of early freshwater algae that were initiating terrestrialization and land plants have evolved multiple branches of this pathway, which give rise to metabolites including lignin, flavonoids, lignans, phenylpropanoid esters, hydroxycinnamic acid amides, and sporopollenin. Recent studies have revealed that many factors participate in the regulation of phenylpropanoid metabolism, and modulate phenylpropanoid homeostasis when plants undergo successive developmental processes and are subjected to stressful environments. In this review, we summarize recent progress on elucidating the contribution of phenylpropanoid metabolism to the coordination of plant development and plant-environment interaction, and metabolic flux redirection among diverse metabolic routes. In addition, our review focuses on the regulation of phenylpropanoid metabolism at the transcriptional, post-transcriptional, post-translational, and epigenetic levels, and in response to phytohormones and biotic and abiotic stresses.

Vílchez J.I., Yang Y., He D., Zi H., Peng L., Lv S., Kaushal R., Wang W., Huang W., Liu R., Lang Z., Miki D., Tang K., Paré P.W., Song C., et. al.

Root-associated soil bacteria can strongly influence plant fitness. DNA methylation is an epigenetic mark important to many fundamental biological processes; however, its roles in plant interactions with beneficial microbes remain elusive. Here, we report that active DNA demethylation in Arabidopsis controls root secretion of myo-inositol and consequently plant growth promotion triggered by Bacillus megaterium strain YC4. Root-secreted myo-inositol is critical for YC4 colonization and preferentially attracts B. megaterium among the examined bacteria species. Active DNA demethylation antagonizes RNA-directed DNA methylation in controlling myo-inositol homeostasis. Importantly, we demonstrate that active DNA demethylation controls myo-inositol-mediated mutualism between YC4 and Solanum lycopersicum, thus suggesting a conserved nature of this epigenetic regulatory mechanism. In Arabidopsis and tomato, exudation of myo-inositol by roots is epigenetically controlled by DNA demethylases and is involved in the beneficial recruitment of growth-promoting rhizobacteria.

de Vries F.T., Griffiths R.I., Knight C.G., Nicolitch O., Williams A.

Root-associated microbes can improve plant growth, and they offer the potential to increase crop resilience to future drought. Although our understanding of the complex feedbacks between plant and microbial responses to drought is advancing, most of our knowledge comes from non-crop plants in controlled experiments. We propose that future research efforts should attempt to quantify relationships between plant and microbial traits, explicitly focus on food crops, and include longer-term experiments under field conditions. Overall, we highlight the need for improved mechanistic understanding of the complex feedbacks between plants and microbes during, and particularly after, drought. This requires integrating ecology with plant, microbiome, and molecular approaches and is central to making crop production more resilient to our future climate.

Kostaki K., Coupel-Ledru A., Bonnell V.C., Gustavsson M., Sun P., McLaughlin F.J., Fraser D.P., McLachlan D.H., Hetherington A.M., Dodd A.N., Franklin K.A.

Morcillo R.J., Singh S.K., He D., An G., Vílchez J.I., Tang K., Yuan F., Sun Y., Shao C., Zhang S., Yang Y., Liu X., Dang Y., Wang W., Gao J., et. al.

Koganitsky A., Tworowski D., Dadosh T., Cecchini G., Eisenbach M.

Fumarate, an electron acceptor in anaerobic respiration of Escherichia coli, has an additional function of assisting the flagellar motor to shift from counterclockwise to clockwise rotation, with a consequent modulation of the bacterial swimming behavior. Fumarate transmits its effect to the motor via the fumarate reductase complex (FrdABCD), shown to bind to FliG-one of the motor's switch proteins. How binding of the FrdABCD respiratory enzyme to FliG enhances clockwise rotation and how fumarate is involved in this activity have remained puzzling. Here we show that the FrdA subunit in the presence of fumarate is sufficient for binding to FliG and for clockwise enhancement. We further demonstrate by in vitro binding assays and super-resolution microscopy in vivo that the mechanism by which fumarate-occupied FrdA enhances clockwise rotation involves its preferential binding to the clockwise state of FliG (FliGcw). Continuum electrostatics combined with docking analysis and conformational sampling endorsed the experimental conclusions and suggested that the FrdA-FliGcw interaction is driven by the positive electrostatic potential generated by FrdA and the negatively charged areas of FliG. They further demonstrated that fumarate changes FrdA's conformation to one that can bind to FliGcw. These findings also show that the reason for the failure of the succinate dehydrogenase flavoprotein SdhA (an almost-identical analog of FrdA shown to bind to FliG equally well) to enhance clockwise rotation is that it has no binding preference for FliGcw. We suggest that this mechanism is physiologically important as it can modulate the magnitude of ΔG0 between the clockwise and counterclockwise states of the motor to tune the motor to the growth conditions of the bacteria.

Rolfe S.A., Griffiths J., Ton J.

Plants employ immunological and ecological strategies to resist biotic stress. Recent evidence suggests that plants adapt to biotic stress by changing their root exudation chemistry to assemble health-promoting microbiomes. This so-called ‘cry-for-help’ hypothesis provides a mechanistic explanation for previously characterized soil feedback responses to plant disease, such as the development of disease-suppressing soils upon successive cultivations of take all-infected wheat. Here, we divide the hypothesis into individual stages and evaluate the evidence for each component. We review how plant immune responses modify root exudation chemistry, as well as what impact this has on microbial activities, and the subsequent plant responses to these activities. Finally, we review the ecological relevance of the interaction, along with its translational potential for future crop protection strategies.

Liang H., Sun H., Shao C., Lv B., Zhu J., Cao W., Zhou J., Zhang Y.

Yang X., Deng B., Lu S., Wang C., Liang Y., Liu S.

Glyptostrobus pensilis is an endangered species belonging to the Cupressaceae family. The comprehensive examination of soil characteristics and rhizosphere microbial communities is vital for conservation efforts, as it provides insights into the necessary environmental conditions for safeguarding and ensuring the viability of rare and endangered species. In this study, the diversity and composition of bacterial and fungal communities were compared in the roots and rhizosphere soils of cultivated and wild G. pensilis in Guangxi, China. The results revealed that, at the phylum level, the rhizosphere of cultivated G. pensilis was significantly enriched with Verrucomicrobiota, Acidobacteriota, Glomeromycota, and Chloroflexi, while wild G. pensilis was significantly enriched with Planctomycetota, Basidiomycota, and Ascomycota. Symbiotic network analysis indicated that the bacterial network in the cultivated G. pensilis rhizosphere had higher edge values, average degree, clustering coefficient, and network density, while the fungal network in the wild G. pensilis rhizosphere had higher node values, edge values, average degree, and clustering coefficient. Moreover, functional prediction results suggested that bacteria in cultivated G. pensilis showed higher metabolic activity, with fungi primarily acted as saprotrophs and symbionts. In contrast, bacteria in wild G. pensilis displayed lower metabolic activity, with fungi predominantly functioning as saprotrophs. The analysis linking rhizospheric microbial diversity to soil environmental factors showed a closer association for the wild G. pensilis microbial community, suggesting a stronger influence of soil environmental factors. The Random Forest (RF) highlighted that the total phosphorus and total potassium levels were key influencing factors for rhizospheric microbes in cultivated G. pensilis, while available potassium levels were crucial for those in wild G. pensilis. These differences underscore the significant strategies for G. pensilis in adapting to different habitats, which may be intricately linked to land management practices and soil environmental factors. Among these, phosphorus and potassium are significantly associated with the rhizosphere microorganisms of G. pensilis. Therefore, continuous monitoring of nutrient availability and regular supplementation of phosphorus and potassium fertilizers in the rhizosphere are recommended during the cultivation and ex-situ conservation of G. pensilis.

Kemen A., Kemen E.

Wang Y., Zhao D., Li Z., Zheng H., Li Y., Zheng Y., Zhang C.

ABSTRACTPlant growth‐promoting rhizobacteria (PGPR) are widely recognized for enhancing the absorption of mineral nutrients by crops. While Sphingobium species have been reported as PGPRs, their capacity to improve nitrogen use efficiency (NUE) and the underlying regulatory mechanisms are not yet fully understood. Here, a strain 41R9, isolated from the rhizosphere of N‐deficient rapeseed, was found to significantly enhance the growth performance of rapeseed under both low and normal N conditions. Genomic analysis revealed that strain 41R9 was closely related to Sphingobium yanoikuyae. 15N isotope tracer experiments confirmed that inoculation with strain 41R9 significantly boosted N uptake and translocation in rapeseed roots. Transcriptome profiling demonstrated that strain 41R9 directly upregulated N transporter genes (NRT2.5 and SLAH1/3), facilitating efficient N acquisition. Furthermore, strain 41R9 maintained jasmonic acid (JA) homoeostasis via JAZ‐mediated negative feedback, balancing defense responses and root development, thereby improving the plant's N acquisition capacity in the roots. Metabolomic and in vitro assays further demonstrated that strain 41R9 displayed strong chemotaxis towards kaempferol, a N‐deficiency‐induced root exudate, suggesting kaempferol might as a chemical effector for S. yanoikuyae recruitment. These findings advance our understanding of PGPR‐driven mechanisms in enhancing crop NUE and highlight the potential of harnessing PGPRs for sustainable agriculture.

Liu Y., Zhu J., Liu Z., Zhi Y., Mei C., Wang H.

The increasing emergence and dissemination of multidrug-resistant (MDR) bacterial pathogens have intensified the need for new antibiotics and alternative therapeutic strategies. Flavonoids, a diverse group of bioactive natural compounds found in plants, have shown significant promise as antibacterial agents. Flavonoids inhibit bacterial growth through various mechanisms, including disruption of cell wall synthesis, prevention of biofilm formation, disruption of cell membrane integrity, and inhibition of bacterial efflux pumps. These actions not only reduce bacterial viability but also enhance the efficacy of conventional antibiotics, offering a potential solution to antibiotic resistance. However, challenges such as poor bioavailability limit their clinical application. Recent advances in nanotechnology-based drug delivery systems, chemical modifications, and formulation techniques have shown promise in improving flavonoid bioavailability and therapeutic efficacy. This review evaluates the antibacterial mechanisms of flavonoids, explores their potential synergistic effects with antibiotics, and highlights strategies to overcome bioavailability issues. Our findings underscore the importance of continued research on flavonoids as promising candidates for innovative antibacterial therapies aimed at combating MDR bacterial infections.

Yang H., Kerner P., Liang X., Struhs E., Mirkouei A., You Y.

Abstract Biochar can enhance soil health and plant productivity, but the underlying mechanisms remain elusive. Here we tackled this question through the lens of the rhizosphere using wheat as a model plant. We examined the impact of four feedstocks (corn stover, cattle manure, pine sawdust, or wheat straw) and two application rates. Biochar modulated root metabolism, where amino acid metabolism was the most common, leading to cascade effects on a wide range of secondary metabolites, including many plant signaling molecules involved in plant–microbe interactions. All biochar treatments increased rhizosphere microbial diversity, altered community composition, enhanced microbial interactions, and resulted in potential functional changes. Increased Burkholderiales (denitrifying bacteria) abundance and decreased Thermoplasmata (archaeal methanogens) abundance could explain biochar’s widely reported effects of mitigating nitrous oxide and methane. Biochar enhanced positive correlations among microbes and network modularity, suggesting local adaptation through synergism and the formation of modules of functionally interrelated taxa. A diversity of keystone taxa from dominant and non-dominant phyla emerged, including those known to mediate methane, nitrogen, and sulfur cycling. Treatment-specific alterations also occurred, and biochar feedstock choice exerted greater influence than application rate. Wheat biochar at 0.25% showed the strongest and distinct modulating effects, resulting in orchestrated changes in root metabolome and rhizosphere microbiome, especially those relevant to plant–microbe interactions and plant growth promotion. Our work provides new insights into the potential of top-down rhizosphere microbiome engineering through biochar-based reprogramming of root-microbe interactions. Graphical Abstract

Chen S., Li R., Lv B., Li Y., Li J., Zhang M., Ma X., Wang C., Xu R., Wang Y., Liao H., Zhong Y.

Lin P., Wang J., Chen P., Fu Z., Luo K., Li Y., Pu T., Wang X., Yong T., Yang W.

BackgroundLegumes, in the initial event of symbiosis, secrete flavonoids into the rhizosphere to attract rhizobia. This study was conducted to investigate the relationship between crop root exudates and soybean nodule development under intercropping patterns.MethodA two years field experiments was carried out and combined with pot experiments to quantify the effects of planting mode, i.e., relay intercropping and monocropping, and genotypes, i.e., supernodulating NTS1007(NTS), Nandou-12(ND) and Guixia-3(GX) on root exudates, rhizobium community structure, nodule development and nitrogen fixation ability.ResultThe result demonstrated that, maize–soybean relay strip intercropping not only promoted daidzein and genistein exudates of soybean root to soil but also reshaped the community structure and diversity of nodule endophytic rhizobia. Compared with monocropping, the nodule number significantly decreased in relay strip intercropping soybean, and NTS achieved 97% at soybean five trifoliolate stage. At soybean full bloom stage, despite the nodulation capacity of relay strip intercropping soybean was unrestored, the nodule number, nodule dry weight, nodule diameter and root dry weight were the highest in ND under relay strip intercropping. Compared with monocropping, the nodule average diameters of ND and GX in relay strip intercropping significantly increased 26.30% and 21.11%, respectively, the single nodule nitrogenase activity and nifH gene was increased up to the higher level of 3.16-fold and 1.96-fold, 70.8% and 107.6%, respectively. Combined with pot experiments, the nodule number of ND and NTS in maize root maize root exudates (RE) treatment increased with growth period, the GX reached its maximum at full bloom stage. And the nodule diameter of ND under RE treatment showed the best response. At R2 stage, compared with distilled water (DW) treatment, the nodule average diameter of ND and GX in RE treatment was significantly higher, and the GmEXPB2 gene was significantly up-regulated 3.99-fold and 1.02-fold, respectively.ConclusionIn brief, the maize–soybean relay strip intercropping enhanced the soybean root exudates nodulation signaling molecules, meanwhile, maize root exudates caused increased nodule diameter, and enhanced nodule nitrogen fixation, but had little effect on supernodulation varieties.

Senizza B., Araniti F., Lewin S., Wende S., Kolb S., Lucini L.

The impact of combined heat and drought stress was investigated in Arabidopsis thaliana and compared to individual stresses to reveal additive effects and interactions. A combination of plant metabolomics and root and rhizosphere bacterial metabarcoding were used to unravel effects at the plant holobiont level. Hierarchical cluster analysis of metabolomics signatures pointed out two main clusters, one including heat and combined heat and drought, and the second cluster that included the control and drought treatments. Overall, phenylpropanoids and nitrogen-containing compounds, hormones and amino acids showed the highest discriminant potential. A decrease in alpha-diversity of Bacteria was observed upon stress, with stress-dependent differences in bacterial microbiota composition. The shift in beta-diversity highlighted the pivotal enrichment of Proteobacteria, including Rhizobiales, Enterobacteriales and Azospirillales. The results corroborate the concept of stress interaction, where the combined heat and drought stress is not the mere combination of the single stresses. Intriguingly, multi-omics interpretations evidenced a good correlation between root metabolomics and root bacterial microbiota, indicating an orchestrated modulation of the whole holobiont.

Sun C., Sun B., Chen L., Zhang M., Lu P., Wu M., Xue Q., Guo Q., Tang D., Lai H.

Wen X., Xiang L., Harindintwali J.D., Wang Y., He C., Fu Y., Wei S., Hashsham S.A., Jiang J., Jiang X., Wang F.

Cao L., Wang D., Wang C., Zhang W., Chen F., Ullah Y., Sun K., Dai C.

Endophytes play an important role in promoting plant growth. To date, although many reports provided insight into the function of endophytes in their hosts, few reports focus on their impact on nearby plants. Intraspecific allelopathy in plant community is common and presents a notable challenge to medicinal plant yield and productivity. Atractylodes lancea is a perennial herb that has relatively low yields due to intraspecific allelopathy. The bacterial endophyte Pseudomonas fluorescens ALEB7B has previously been found to increase essential oil content of A. lancea, but the role of ALEB7B in A. lancea allelopathy is still unknown. Noninoculated A. lancea exhibited growth retardation when it was grown in a community, which was related to ethylene-induced intraspecific allelopathy. Further experiment showed that exposing A. lancea to volatile from noninoculated A. lancea or same concentration of ethylene reduced growth of A. lancea. P. fluorescens-inoculated plants showed reduced ethylene emission and relieved growth retardation on neighboring noninoculated A. lancea. Moreover, P. fluorescens inoculation had little allelopathic effect when receivers were treated with ethylene receptor inhibitor or when emitters were treated with ethylene production inhibitor. Transcriptomic analysis revealed that endophyte ALEB7B altered transcriptional response associated with ethylene response and essential oil production in neighboring A. lancea. Our results demonstrated that the bacterial endophyte ALEB7B provides fitness benefits for both hosts and neighbors. The allelopathic effect on nearby plants can be alleviated by altering airborne signals, such as ethylene, in endophytic bacteria.

Lin J., Dai H., Yuan J., Tang C., Ma B., Xu J.

Heavy metal contamination poses an escalating global challenge to soil ecosystems, with hyperaccumulators playing a crucial role in environmental remediation and resource recovery. The enrichment of diazotrophs and resulting nitrogen accumulation promoted hyperaccumulator growth and facilitated phytoremediation. Nonetheless, the regulatory mechanism of hyperaccumulator biological nitrogen fixation has remained elusive. Here, we report the mechanism by which arsenic regulates biological nitrogen fixation in the arsenic-hyperaccumulator Pteris vittata. Field investigations and greenhouse experiments, based on multi-omics approaches, reveal that elevated arsenic stress induces an enrichment of key diazotrophs, enhances plant nitrogen acquisition, and thus improves plant growth. Metabolomic analysis and microfluidic experiments further demonstrate that the upregulation of specific root metabolites plays a crucial role in recruiting key diazotrophic bacteria. These findings highlight the pivotal role of nitrogen-acquisition mechanisms in the arsenic hyperaccumulation of Pteris vittata, and provide valuable insights into the plant stress resistance. Elevated arsenic is found to enhance plant nitrogen acquisition and plant growth of the arsenic hyperaccumulator Pteris vittate. Multi-omics analysis reveals the interaction between root metabolites and key diazotrophs underlying this effect.

Srivastava A.K., Singh R.D., Pandey G.K., Mukherjee P.K., Foyer C.H.

ABSTRACTPlants are an intrinsic part of the soil community, which is comprised of a diverse range of organisms that interact in the rhizosphere through continuous molecular communications. The molecular dialogue within the plant microbiome involves a complex repertoire of primary and secondary metabolites that interact within different liquid matrices and biofilms. Communication functions are likely to involve membrane‐less organelles formed by liquid−liquid phase separation of proteins and natural deep eutectic solvents that play a role as alternative media to water. We discuss the chemistry of inter‐organism communication and signalling within the biosphere that allows plants to discriminate between harmful, benign and beneficial microorganisms. We summarize current information concerning the chemical repertoire that underpins plant−microbe communication and host‐range specificity. We highlight how the regulated production, perception and processing of reactive oxygen species (ROS) is used in the communication between plants and microbes and within the communities that shape the soil microbiome.

Zhang J., Jia F., Song K., Wang F., Li J., Huang L., Qu T.

Drought is the primary factor limiting rice production in ecosystems. Wild rice rhizosphere bacteria possess the potential to assist in the stress resistance of cultivated rice. This study examines the impact of wild rice rhizosphere bacteria on cultivated rice under drought conditions. From the rhizosphere soil of wild rice, 20 potential drought-resistant strains were isolated. Subsequent to the screening, the most effective strain b3, was identified as Enterobacter ludwigii. Pot experiments were conducted on the cultivated Changbai 9 rice. It was found that inoculation with the E. ludwigii b3 strain improved the drought resistance of the rice, promotion of rice growth (shoot height increased by 13.47 %), increased chlorophyll content (chlorophyll a, chlorophyll b and carotenoid increased by 168.74 %, 130.68 % and 87.89 %), improved antioxidant system (content of glutathione was increased by 60.35 %), and accumulation of osmotic regulation substances (soluble sugar and soluble protein increased by 70.36 % and 142.03 %). Furthermore, E. ludwigii b3 had a transformative effect on the rhizosphere bacterial community of cultivated rice, increasing its abundance and diversity while simultaneously recruiting beneficial rhizosphere bacteria, resulting in a more complex community. Additionally, E. ludwigii b3 acted directly and indirectly on cultivated rice through its metabolites (organic acids, amino acids, flavonoids and other substances), which helped alleviate drought stress. In conclusion, the E. ludwigii b3 shows promise as a drought-resistant strain and has the potential to improve the growth and productivity of cultivated rice in arid agricultural ecosystems. This study represents the first investigation of E. ludwigii in the rhizosphere of wild rice under drought conditions on cultivated rice.