Root exudates facilitate the regulation of soil microbial community function in the genus Haloxylon.

Introduction: Root exudates act as the "language" of plant-soil communication, facilitating crucial interactions, information exchange, and energy transfer between plants and soil. The interactions facilitated by root exudates between plants and microorganisms in the rhizosphere are crucial for nutrient uptake and stress resilience in plants. However, the mechanism underlying the interaction between root exudates and rhizosphere microorganisms in desert plants under drought conditions remains unclear, especially among closely related species. Methods: To reveal the ecological strategies employed by the genus Haloxylon in different habitats. Using DNA extraction and sequencing and UPLC-Q-Tof/MS methods, we studied root exudates and soil microorganisms from two closely related species, Haloxylon ammodendron (HA) and Haloxylon persicum (HP), to assess differences in their root exudates, soil microbial composition, and interactions. Results: Significant differences were found in soil properties and root traits between the two species, among which soil water content (SWC) and soil organic carbon (SOC) in rhizosphere and bulk soils (P < 0.05). While the metabolite classification of root exudates was similar, their components varied, with terpenoids being the main differential metabolites. Soil microbial structure and diversity also exhibited significant differences, with distinct key species in the network and differential functional processes mainly related to nitrogen and carbon cycles. Strong correlations were observed between root exudate-mediated root traits, soil microorganisms, and soil properties, although the complex interactions differed between the two closely relative species. The primary metabolites found in the network of HA include sugars and fatty acids, while HP relies on secondary metabolites, steroids and terpenoids. Discussion: These findings suggest that root exudates are key in shaping rhizosphere microbial communities, increasing microbial functionality, fostering symbiotic relationships with hosts, and bolstering the resilience of plants to environmental stress.

Pepper root exudate alleviates cucumber root-knot nematode infection by recruiting a rhizobacterium.

Root-knot nematodes (Meloidogyne spp.) have garnered significant attention from researchers due to their substantial damage to crops and worldwide distribution. However, controlling this nematode disease is challenging which results from limited chemical pesticides and biocontrol agents effective against them. Here, we demonstrate that pepper-rotation markedly reduces Meloidogyne incognita infection in cucumber and diminishes the presence of p-hydroxybenzoic acid in the soil, a compound known to exacerbate M. incognita infection. Pepper-rotation also structures the rhizobacterial community, leading to the colonization of two Pseudarthrobacter oxydans strains (RH60 and RH97) in the cucumber rhizosphere, facilitated by palmitic acid enrichment in pepper root exudates. Furthermore, both strains exhibit high nematocidal activity against M. incognita, and possess the ability to biosynthesize indoleacetic acid and biodegrade p-hydroxybenzoic acid. RH60 and RH97 additionally induce systemic resistance in cucumber plants and promote their growth. These data suggest that pepper root-exudate palmitic acid alleviates M. incognita infection by recruiting beneficial P. oxydans in the cucumber rhizosphere. Our analyses identify a novel chemical component in root exudates and uncover its pivotal role in crop rotation for disease attenuation, providing intriguing insights into the keystone function of root exudates in plant protection against root-knot nematode infection.

A "love match" score to compare root exudate attraction and feeding of the plant growth-promoting rhizobacteria Bacillus subtilis, Pseudomonas fluorescens, and Azospirillum brasilense.

Introduction: The rhizosphere is the zone of soil surrounding plant roots that is directly influenced by root exudates released by the plant, which select soil microorganisms. The resulting rhizosphere microbiota plays a key role in plant health and development by enhancing its nutrition or immune response and protecting it from biotic or abiotic stresses. In particular, plant growth-promoting rhizobacteria (PGPR) are beneficial members of this microbiota that represent a great hope for agroecology, since they could be used as bioinoculants for sustainable crop production. Therefore, it is necessary to decipher the molecular dialog between roots and PGPR in order to promote the establishment of bioinoculants in the rhizosphere, which is required for their beneficial functions. Methods: Here, the ability of root exudates from rapeseed (Brassica napus), pea (Pisum sativum), and ryegrass (Lolium perenne) to attract and feed three PGPR (Bacillus subtilis, Pseudomonas fluorescens, and Azospirillum brasilense) was measured and compared, as these responses are directly involved in the establishment of the rhizosphere microbiota. Results: Our results showed that root exudates differentially attracted and fed the three PGPR. For all beneficial bacteria, rapeseed exudates were the most attractive and induced the fastest growth, while pea exudates allowed the highest biomass production. The performance of ryegrass exudates was generally lower, and variable responses were observed between bacteria. In addition, P. fluorescens and A. brasilense appeared to respond more efficiently to root exudates than B. subtilis. Finally, we proposed to evaluate the compatibility of each plant-PGPR couple by assigning them a "love match" score, which reflects the ability of root exudates to enhance bacterial rhizocompetence. Discussion: Taken together, our results provide new insights into the specific selection of PGPR by the plant through their root exudates and may help to select the most effective exudates to promote bioinoculant establishment in the rhizosphere.

The quantification of root exudation by an in-situ method based on root morphology over three incubation periods.

Investigating the quantity and spatiotemporal dynamics of metabolite release from plant roots is essential if we are to understand the ecological significance of root exudates in the rhizosphere; however, this is difficult to quantify. In the present study, we quantified in situ root exudation rates during three incubation periods (0-24, 24-48, and 48-72 h) and fine roots within four diameter ranges (<0.8, 0.8-1.0, 1.0-1.2, and 1.2-2.0 mm), and also measured nine morphological traits in the fine roots of Pinus massoniana. Higher root carbon (C) exudation rates were detected during the 0-24 h period. During the 0-24 h and 24-48 h periods, nitrogen (N) uptake rates were higher than N exudation rates, while during the 48-72 h period, N exudation rates exceeded uptake rates. As C exudation increased during 0-48h incubation period, the uptake of N tended to level out. We concluded that the 24-48 h incubation period was the most suitable for capturing root exudates from P. massoniana. The exudation of C from the roots was positively associated with root mass, length, surface area, volume, the number of root tips, and the root tissue density, when incubated for 0-24 h and 24-48 h. Furthermore, length-specific C exudation rates, along with N exudation and uptake rates, all increased as the diameter of the fine roots increased. The release of root exudates could be efficiently predicted by the fine root morphological traits, although the accuracy of prediction depended on the incubation period. Higher values for fine root morphological traits were generally indicative of higher nutrient requirements and tissue investment, as well as higher C exudation rates.

Two grasses differ in their absorptive root physiological traits and rooting depth under drought in an alpine steppe.

BACKGROUND AND AIMS: Absorptive root traits play important roles in acquisition of water and nutrients from soil by plants. Despite numerous reports on the changes in species dominance under long-term drought in grassland community, few studies have specifically investigated absorptive root traits of these dominant species in grasslands, especially in the alpine grasslands. METHODS: Here, two grass species (Leymus secalinus and Stipa purpurea) differing in their responses to drought were selected from an alpine steppe. A series of absorptive root traits were examined under drought in a 3-year glasshouse experiment. KEY RESULTS: We found that drought had no effects on root morphological and architectural traits, whereas root physiological traits and rooting depth differed in their responses to drought. Specifically, drought significantly reduced root respiration and enhanced organ carbon (C) exudation rate, carboxylate exudation rate, acid phosphatase activity and rooting depth of L. secalinus. Particularly, L. secalinus released more citrate into the rhizosphere under drought than S. purpurea. In contrast, these root traits of S. purpurea remained relatively unchanged in response to the drought. These differential responses would render L. secalinus more competitive in acquisition of nutrients and water, thus contributing to its dominance in the community under drought. Moreover, root respiration was negatively correlated with organic C exudation rate, carboxylate exudation rate and acid phosphatase activity, indicating a tradeoff between root respiration and root exudates to acquire nutrients and water by optimizing C allocation under drought. Additionally, all root traits exhibited two independent dimensions in root economic space (RES) for both species under drought. CONCLUSIONS: These results indicate that the plant species with great capacity to acquire water and nutrients in soil by optimizing C allocation under drought will be dominant in the community of the alpine grasslands. These findings provide an important insight into species re-ordering under drought on the Tibetan Plateau.

Effectiveness of dexamethasone implants in treating diabetic macular edema with hard exudates: a clinical observation.

OBJECTIVE: This study seeks to explain the relationship between systemic conditions and hard exudate formations in diabetic macular edema patients. Besides, the study aimed to quantitatively examine changes in the area, location, and impact on visual function of hard exudates following intravitreal dexamethasone implant injections. METHODS: A retrospective analysis was conducted, including 40 patients (40 eyes) diagnosed with non-proliferative diabetic retinopathy and concurrent macular edema between January 1, 2022, and January 1, 2024. Preoperative evaluations included glycated hemoglobin, lipid profile, and renal function examinations. Based on the location of HE, patients were divided into two groups: Group A, with HE in 1 mm of the central fovea, and Group B, with HE outside 1 mm of the central fovea. Selected eyes were subject to pre- and postoperative examinations, including best-corrected visual acuity (BCVA), intraocular pressure, slit-lamp biomicroscopy, scanning laser ophthalmoscopy (SLO), optical coherence tomography, and multifocal electroretinography. Following screening and examination, patients received an immediate intravitreal injection of the DEX implant, with an injection administered at the four-month mark. Hard exudate (HE) areas were measured utilizing SLO fundus imaging. RESULTS: Total cholesterol, low-density lipoprotein, and triglyceride levels were found to be positively correlated with the presence of HE. Following surgical intervention, all patients demonstrated an improvement in BCVA. The mean BCVA increased from a preoperative measurement of 0.79 ± 0.04 to 0.39 ± 0.02 at the 6 month follow-up, indicating a statistically significant difference (p < 0.001). The baseline HE area for the entire patient cohort was 2.28 ± 0.22. One month post-operation, the HE area exhibited a slight increase to 2.27 ± 0.22. However, by the 6 month follow-up, the HE area had significantly decreased to 0.8 ± 0.87, representing a 35.09% reduction from the baseline measurement (p < 0.001). It is worth noting that Patient P1 did not exhibit a statistically significant difference between preoperative and six-month postoperative HE area (p = 0.032). Preoperative BCVA measurements for Group A and Group B were 0.81 ± 0.03 and 0.77 ± 0.03, respectively, with no statistically significant intergroup difference (p = 0.333). The baseline HE area for Group A was 2.61 ± 0.16, which decreased to 0.38 ± 0.20 at the six-month follow-up, representing a 14.60% reduction from the baseline total area. For Group B, the baseline HE area was measured at 1.95 ± 0.09, then decreasing to 1.21 ± 0.13 at the six-month follow-up, indicating a 62.05% reduction from the baseline total area. A statistically significant difference in the postoperative 6 month HE area was observed between Group A and Group B (p < 0.001). In Group A, the reduction in HE area (initial HE area-final HE area) was positively correlated with the improvement in P1 (initial P1-final P1) (r = 0.610, p = 0.004). In Group B, a similar positive correlation was found (initial HE area-final HE area with initial P1-final P1) (r = 0.488, p = 0.029). In Group B, the reduction in HE area (initial HE area-final HE area) correlated positively with the improvement in BCVA (initial BCVA-final BCVA) (r = 0.615, p = 0.004). Additionally, in Group B, the reduction in HE area (initial HE area-final HE area) was positively correlated with the improvement in CMT (initial CMT-final CMT) (r = -0.725, p< 0.001). Aggravated cataracts were observed in thirteen eyes during a follow-up examination 6 months later. CONCLUSION: HE formation is associated with lipid levels. Dexamethasone implants demonstrate effectiveness in reducing HE areas in the short term, reducing macular edema, improving retinal structure, and enhancing visual function. The incidence of postoperative complications such as cataracts and glaucoma remains low.

Impacts of root exudates on the toxic response of Chrysanthemum coronarium L. to the co-pollution of nanoplastic particles and tetracycline.

Nano polystyrene (PS) particles and antibiotics universally co-exist, posing a threat to crop plants and hence human health, nevertheless, there is limited research on their combined toxic effects along with major influential factors, especially root exudates, on crop plants. This study aimed to investigate the response of Chrysanthemum coronarium L. to the co-pollution of nanoplastics and tetracycline (TC), as well as the effect of root exudates on this response. Based on a hydroponic experiment, the biochemical and physiological indices of Chrysanthemum coronarium L. were measured after 7 days of exposure. Results revealed that the co-pollution of TC and PS caused significant oxidative damage to the plants, resulting in reduced biomass. Amongst the two contaminants, TC played a more prominent role. PS could enter the root tissue, and the uptake of TC and PS by plant roots was synergetic. Malic acid, oxalic acid, and formic acid could explain 65.1% of the variation in biochemical parameters and biomass of the roots. These compounds affected the photosynthesis and biomass of Chrysanthemum coronarium L. by gradually lowering root reactive oxygen species (ROS) and leaf ROS. In contrast, the impact of rhizobacteria on the toxic response of the plants was relatively minor. These findings suggested that root exudates could alleviate the toxic response of plants to the co-pollution of TC and PS. This study enhances our understanding of the role of root exudates, providing insights for agricultural management and ensuring food safety.

Subretinal Exudation: The First Presentation of Untreated Choroidal Melanomas.

Introduction: This case series aims to present the unusual clinical manifestation of subretinal exudation in patients diagnosed with untreated choroidal melanoma. A total of 886 patients were diagnosed and treated for primary choroidal melanoma between November 2017 and June 2023 at St. Paul's Eye Unit, Royal Liverpool University Hospital, UK. The fundus photographs were screened for lipid exudates by two independent clinical experts. The patients' demographics, clinical manifestations, and imaging features were analysed, whereas the location of exudation was documented with fundus photographs and optical coherence tomography (OCT). The histopathological and genetic results were also analysed in cases with tumour biopsy available. Case Presentations: Eight cases with subretinal exudates were identified (n = 8/886, 0.90%). No gender predilection was noticed (male/female 1:1), whereas the mean age was 51 years (range 39-79). Four patients were asymptomatic at presentation, 2 patients reported reduced visual acuity, and 2 patients presented with photopsia. OCT scans revealed the presence of subretinal fluid and subretinal exudates, while the ultrasound showed medium or low internal reflectivity in 7 out of 8 cases. The biopsy analysis was available in 4 cases, all showing low-risk spindle cell choroidal melanoma with disomy 3. Conclusion: Lipid exudates are an atypical fundoscopic finding in patients with untreated choroidal melanoma. The subretinal location could differentiate them from other retinal vascular conditions and facilitate early diagnosis and intervention. Interestingly, all cases tested cytogenetically were of low metastatic risk; these exudates may, therefore, be a positive clinical prognostic sign.

Organic matter excreted by the protozoan Tetrahymena thermophila and its effects on the bioaccumulation of nanoparticles.

Although organic matter (exudate) excreted by aquatic organisms is an important component of dissolved organic matter (DOM) in the natural environment, its potential effects on the bioaccumulation of nanoparticles (NPs) remain unclear. In the present study, we examined the effects of the exudates from the protozoan Tetrahymena thermophila on the bioaccumulation (including uptake and cell surface adsorption) of iron oxide (Fe2O3, polyacrylate coated) and silica (SiO2) NPs in T. thermophila. The exudates were mostly (93.6 %, in carbon) composed of < 1-kDa molecules (e.g., lipids). When the exudates were mixed with the NPs, significant adsorption occurred on SiO2 NPs but not on Fe2O3 NPs. Independent of their adsorption by the NPs, the exudates significantly inhibited the bioaccumulation of both SiO2 NPs and Fe2O3 NPs by T. thermophila. This inhibitory effect was shown to be mainly due to their inhibition of NP adsorption on the cell surface. By contrast, the exudates had negligible effects on the uptake of either NP type, most likely due to their low molecular weight. Since DOM in the aquatic environment is dominated by molecules < 1 kDa, the potential effects of low-molecular-weight DOM, such as exudates from aquatic organisms, on the bioaccumulation of NPs merits greater attention. ENVIRONMENTAL IMPLICATION: Nanoparticles (NPs) are hazardous materials widespread in the natural environment. Previous studies showed that dissolved organic matter (DOM) in aquatic environments determine the environmental behavior and ecological effects of NPs. Although organic matter (exudate) excreted by aquatic organisms is an important component of DOM, its potential effects on the bioaccumulation of NPs remain unclear. In the present study, we found that the exudates inhibited the cell-surface adsorption of NPs but had no effects on NP uptake, as different from the well-known effects of DOM on NP bioaccumulation. This finding merits attention during evaluations of the environmental risks of NPs.

The combined toxicity of polystyrene microplastic and arsenate: From the view of biochemical process in wheat seedlings (Triticum aestivum L.).

Microplastics (MPs) are important carriers of various toxic metals and can alter their toxicity pattern in agricultural soil, leading to combined pollution, therefore posing new challenges to soil pollution management and environmental risk assessment. In this study, we observed the internalization of MPs in plants and conducted incubation experiments to evaluated the effects of arsenate (As(V)) alone and in combination with polystyrene (PS) MPs on wheat seedlings (Triticum aestivum L.). Under As(V) alone and combined with PS-MP exposure, dose-dependent toxicity in terms of root and stem elongation and biomass accumulation was observed. Compared with As(V) alone, the presence of PS-MPs reduced the accumulation of As in wheat roots by 11.43-58.91%, but PS-MPs intensified the transport of As to the aboveground parts of wheat, increasing As accumulation in wheat stems by 27.77-1011.54%. This causes more serious mechanical damage and oxidative stress to plant cells, increasing the accumulation of reactive oxygen species and lipid peroxidation in wheat roots and upregulating the activities of antioxidant enzymes such as superoxide dismutase (SOD) and peroxidase (POD). In addition, the co-exposure of As(V) and PS-MPs disrupts the photosynthetic system of wheat leaves and the secretion activities of roots. Therefore, the combination of As(V) and PS-MPs caused greater damage to wheat growth. Our findings contribute to a more comprehensive assessment of the combined toxicity of MPs and heavy metal to crops.

Root exudate-assisted phytoremediation of copper and lead contamination using Rumex acetosa L. and Rumex K-1.

Heavy metal pollutants can be effectively removed from soil through phytoremediation using root exudates. Herein, experiments were conducted to assess the phytoremediation capabilities of Rumex acetosa L. and Rumex K-1 root exudates for copper (Cu) and lead (Pb) contamination. Results indicated that these root exudates effectively adsorbed Cu and Pb. Furthermore, the optimal adsorption conditions of Cu by the root exudates of both plants were as follows: light duration of 36 h, light intensity of 8000 Lx, temperature of 25 °C and CO(NH2)2 concentration of 0 %. Moreover, the optimal adsorption conditions of Pb by Rumex acetosa L. and Rumex K-1 root exudates were light duration of 48 h and 24 h, respectively, light intensity of 8000 Lx, temperature of 25 °C and CO(NH2)2 concentration of 0 %. In addition, the root exudates from both plants enhanced the enrichment and transport of Cu and Pb. Moreover, the root was found to be the main accumulation site of Pb, while the stems and leaves were the main accumulation sites of Cu. With the application of root exudates, plant growth increased, with growth indices in Rumex acetosa L. and Rumex K-1 groups treated with exudates being 1.08-1.81-fold and 1.06-1.9-fold higher, respectively, compared with the untreated ones; physiological indexes showed 1.14-2.62-fold and 1.14-2.71-fold improvements, respectively. Remediation efficiency indexes showed 1.05-1.62-fold and 1.10-1.89-fold improvements, respectively. Rumex acetosa L. and Rumex K-1 exhibited promising potential for the phytoremediation of Cu and Pb, with root exudates playing a critical role in metal adsorption and stabilisation, suggesting their potential for enhancing remediation capabilities. This study sheds light on the mechanisms of root exudate-assisted phytoremediation and provides insights into alleviating heavy metal pollution.

Phenoxyacetic acid enhances nodulation symbiosis during the rapid growth stage of soybean.

Root exudates are known signaling agents that influence legume root nodulation, but the molecular mechanisms for nonflavonoid molecules remain largely unexplored. The number of soybean root nodules during the initial growth phase shows substantial discrepancies at distinct developmental junctures. Using a combination of metabolomics analyses on root exudates and nodulation experiments, we identify a pivotal role for certain root exudates during the rapid growth phase in promoting nodulation. Phenoxyacetic acid (POA) was found to activate the expression of GmGA2ox10 and thereby facilitate rhizobial infection and the formation of infection threads. Furthermore, POA exerts regulatory control on the miR172c-NNC1 module to foster nodule primordia development and consequently increase nodule numbers. These findings collectively highlight the important role of POA in enhancing nodulation during the accelerated growth phase of soybeans.

Plant and soil characteristics affected by the allelopathic pathways of Avena fatua and Lolium temulentum weeds.

The potential of the most prevalent weeds should be characterized biologically and chemically in infected soil and crops for sustainable agriculture. Therefore, the allelopathic potential of Avena fatua L. and Lolium temulentum L. weeds were compared via leachates, root exudates, decayed residues in soil, and the decomposition in water pathways. Chemical measurements were taken on wheat (Triticum aestivum L.), and soil decomposed solution. Based on EC50, the allelopathic effect of leachates were higher in aboveground parts than in subterranean parts, influenced by plant parts and concentrations. The root exudates show EC50 by 655.9 µg. ml-1 for A. fatua and 625.66 µg. ml-1 for L. temulentumin the seedling biomass fresh weights of T. aestivum. The systematic inhibition by decayed residues was affected by plant types, concentration, and time and correlated with soil parameters and crop performance. The decomposition rate was higher under aerobic conditions than anaerobic conditions, with the inhibition pattern showing the reverse trend. These finding highlight the importance of environmental conditions in mediating allelopathic effects. The highest quantities of phenolic acids determined by LC-ES/MS in decomposed solutions were citric acid, with concentrations of 7.71 and 13.31 µg/ml in A. fatua under aerobic conditions, and coumaric acid, with concentrations of 9.21 and 16.99 µg/ml in L. temulentum under aerobic conditions. The allelopathic potentials of A. fatua and L. temulentum may play a crucial role in T. aestivum crop growth and soil parameters. In general weed residues can suppress crop growth and negatively affect soil parameters based on their quantity and type, therefore they should be managed carefully for sustainable crop production.

Plant-nematode battle: engagement of complex signaling network.

Plant-parasitic nematodes (PPNs) are widely distributed and highly adaptable. To evade the invasion and infection of PPNs, plants initiate a series of defense responses. In turn, PPNs secrete effectors into the host tissues to suppress plant defense. In this ongoing battle between PPNs and plants, complex signal transduction processes are typically involved. This article aims to review the plant signaling network involved in host perception by the nematode, nematode perception, and downstream activation of plant defense signaling and how nematodes attempt to interfere with this network. Our goal is to establish a foundation for elucidating the signaling and regulatory mechanisms of plant-nematode interactions, and to provide insights and tools for developing PPN-resistant crops and technologies.

Selenium improved arsenic toxicity tolerance in two bell pepper (Capsicum annuum L.) varieties by modulating growth, ion uptake, photosynthesis, and antioxidant profile.

Bell pepper (Capsicum annuum L.); an important spice crop of the region is a rich source of vitamins and antioxidants having many health benefits. Many biotic and abiotic factors contribute towards growth and yield losses of this crop. Arsenic (As) toxicity is a global issue, but it is particularly critical in developing countries. The current study was designed to evaluate the efficacy of selenium (Se) in mitigating the toxic effects of As in two varieties (HSP-181 A and PS09979325) of Capsicum annuum L. Different concentrations of As (0, 50, and 100 µM) and Se (0, 5, and 10 µM) were tested using 14 days old seedlings of C. annuum L. The As stress caused a significant (P ≤ 0.001) reduction in growth, uptake of nutrients, and eco-physiological attributes in both varieties however, the response was specific. While the overproduction of osmo-protectants and antioxidants intensified the symptoms of oxidative stress. The maximum reduction in shoot length (45%), fresh weight (29%), and dry weight (36%) was observed in under 100 µM As stress. The organic acids exudation from the roots of both cultivars were significantly increased with the increase in As toxicity. The Se treatment significantly (p ≤ 0.001) improved growth, nutrient uptake, gas exchange attributes, antioxidant production, while decreased oxidative stress indicators, and As uptake in the roots and shoots of all the subjects under investigation. It is concluded from the results of this study that Se application increased photosynthetic efficiency and antioxidant activity while decreasing As levels, organic acid exudation, and oxidative stress indicators in plants. Overall, the var. PS09979325 performed better and may be a good candidate for future pepper breeding program.

The drought-induced plasticity of mineral nutrients contributes to drought tolerance discrimination in durum wheat.

Drought is a major challenge for the cultivation of durum wheat, a crucial crop for global food security. Plants respond to drought by adjusting their mineral nutrient profiles to cope with water scarcity, showing the importance of nutrient plasticity for plant acclimation and adaptation to diverse environments. Therefore, it is essential to understand the genetic basis of mineral nutrient profile plasticity in durum wheat under drought stress to select drought-tolerant varieties. The research study investigated the responses of different durum wheat genotypes to severe drought stress at the seedling stage. The study employed an ionomic, molecular, biochemical and physiological approach to shed light on distinct behaviors among different genotypes. The drought tolerance of SVEMS16, SVEVO, and BULEL was related to their capacity of maintaining or increasing nutrient's accumulation, while the limited nutrient acquisition capability of CRESO and S.CAP likely resulted in their susceptibility to drought. The study highlighted the importance of macronutrients such as SO42-, NO3-, PO43-, and K+ in stress resilience and identified variant-containing genes potentially influencing nutritional variations under drought. These findings provide valuable insights for further field studies to assess the drought tolerance of durum wheat genotypes across various growth stages, ultimately ensuring food security and sustainable production in the face of changing environmental conditions.

Chitooligosaccharides and Arbuscular Mycorrhizal fungi alleviate the damage by Phytophthora nicotianae to tobacco seedlings by inducing changes in rhizosphere microecology.

Arbuscular mycorrhizal fungi (AMF) and Chitooligosaccharide (COS) can increase the resistance of plants to disease. COS can also promote the symbiosis between AMF and plants. However, the effects of AMF & COS combined application on the rhizosphere soil microbial community of tobacco and the improvement of tobacco's resistance to black shank disease are poorly understood.·We treated tobacco with AMF, COS, and combined application of AMF & COS (AC), respectively. Then studied the incidence, physio-biochemical changes, root exudates, and soil microbial diversity of tobacco seedling that was inoculated with Phytophthora nicotianae. The antioxidant enzyme activity and root vigor of tobacco showed a regular of AC > AMF > COS > CK, while the severity of tobacco disease showed the opposite regular. AMF and COS enhance the resistance to black shank disease by enhancing root vigor, and antioxidant capacity, and inducing changes in the rhizosphere microecology of tobacco. We have identified key root exudates and critical soil microorganisms that can inhibit the growth of P. nicotianae. The presence of caprylic acid in root exudates and Bacillus (WdhR-2) in rhizosphere soil microorganisms is the key factor that inhibits P. nicotianae growth. AC can significantly increase the content of caprylic acid in tobacco root exudates compared to AMF and COS. Both AMF and COS can significantly increase the abundance of Bacillus in tobacco rhizosphere soil, but the abundance of Bacillus in AC is significantly higher than that in AMF and COS. This indicates that the combined application of AMF and COS is more effective than their individual use. These findings suggest that exogenous stimuli can induce changes in plant root exudates, regulate plant rhizosphere microbial community, and then inhibit the growth of pathogens, thereby improving plant resistance to diseases.

Kinetics of uptake, translocation, and metabolism of organophosphate esters in japonica rice (Oryza sativa L.): Hydroponic experiment combined with model.

Hydroponics combined with fugacity model was employed to investigate the kinetics of uptake, accumulation, and metabolism of organophosphate esters (OPEs) by japonica rice. The time-dependent process for uptake and accumulation of 5 OPEs and their diester-metabolites in both rice root and shoot fitted well with the pseudo-first-order kinetic model. The peak OPE accumulations in rice root and shoot were significantly positively or negatively correlated with their octanol-water partition coefficient (logKow) respectively, but not for their apparent accumulation rates. Root concentration factors (RCFs) and root-to-shoot translocation factors (TFs) of OPEs were found to be positively and negatively correlated with their logKow, respectively. Triphenyl phosphate with benzene ring substituents showed the highest RCF, but the lowest TF, because of its high potential for root adsorption due to the π electron-rich structures. Sterilized root exudates can hinder the root adsorption and absorption of OPEs from solution probably through competitive adsorption of OPEs with root surface. The first-hand transport and metabolism rates were also obtained by generating these rates to fit the dynamic fugacity model with the measurement values. The simulation indicated that the kinetics of OPE accumulation in rice plants may be controlled by multiple processes and physicochemical properties besides Kow.

RhizoMAP: a comprehensive, nondestructive, and sensitive platform for metabolic imaging of the rhizosphere.

BACKGROUND: Elucidating the intricate structural organization and spatial gradients of biomolecular composition within the rhizosphere is critical to understanding important biogeochemical processes, which include the mechanisms of root-microbe interactions for maintaining sustainable plant ecosystem services. While various analytical methods have been developed to assess the spatial heterogeneity within the rhizosphere, a comprehensive view of the fine distribution of metabolites within the root-soil interface has remained a significant challenge. This is primarily due to the difficulty of maintaining the original spatial organization during sample preparation without compromising its molecular content. RESULTS: In this study, we present a novel approach, RhizoMAP, in which the rhizosphere molecules are imprinted on selected polymer membranes and then spatially profiled using matrix-assisted laser desorption/ionization (MALDI) mass spectrometry imaging (MSI). We enhanced the performance of RhizoMAP by combining the use of two thin (< 20 µm) membranes (polyester and polycarbonate) with distinct MALDI sample preparations. This optimization allowed us to gain insight into the distribution of over 500 different molecules within the rhizosphere of poplar (Populus trichocarpa) grown in rhizoboxes filled with mycorrhizae soil. These two membranes, coupled with three different sample preparation conditions, enabled us to capture the distribution of a wide variety of molecules that included phytohormones, amino acids, sugars, sugar glycosides, polycarboxylic acids components of the Krebs cycle, fatty acids, short aldehydes and ketones, terpenes, volatile organic compounds, fertilizers from the soil, and others. Their spatial distribution varies greatly, with some following root traces, others showing diffusion from roots, some associated with soil particles, and many having distinct hot spots along the plant root or surrounding soil. Moreover, we showed how RhizoMAP can be used to localize the origin of the molecules and molecular transformation during root growth. Finally, we demonstrated the power of RhizoMAP to capture molecular distributions of key metabolites throughout a 20 cm deep rhizosphere. CONCLUSIONS: RhizoMAP is a method that provides nondestructive, untargeted, broad, and sensitive metabolite imaging of root-associated molecules, exudates, and soil organic matter throughout the rhizosphere, as demonstrated in a lab-controlled native soil environment.

Wheat domestication alters root metabolic functions to drive the assembly of endophytic bacteria.

The domestication process progressively differentiated wild relatives from modern cultivars, thus impacting plant-associated microorganisms. Endophytic bacterial communities play vital roles in plant growth, development, and health, which contribute to the crop's sustainable development. However, how plant domestication impacts endophytic bacterial communities and relevant root exudates in wheat remains unclear. First, we have observed that the domestication process increased the root endophytic microbial community diversity of wheat while decreasing functional diversity. Second, domestication decreased the endophytic bacterial co-occurrence network stability, and it did significantly alter the abundances of core microorganisms or potential probiotics. Third, untargeted LC-MS metabolomics revealed that domestication significantly altered the metabolite profiles, and the abundances of various root exudates released were significantly correlated with keystone taxa including the Chryseobacterium, Massilia, and Lechevalieria. Moreover, we found that root exudates, especially L-tyrosine promote the growth of plant-beneficial bacteria, such as Chryseobacterium. Additionally, with L-tyrosine and Chryseobacterium colonized in the roots, the growth of wild wheat's roots was significantly promoted, while no notable effect could be found in the domesticated cultivars. Overall, this study suggested that wild wheat as a key germplasm material, and its native endophytic microbes may serve as a resource for engineering crop microbiomes to improve the morphological and physiological traits of crops in widely distributed poor soils.