BackgroundBeauveria bassiana is an entomopathogenic fungus that can establish an intimate endophytic relationship with plants. Otherwise, microbial volatile organic compounds (VOCs) are important chemicals for plant recognition and interactions. Therefore, this study provides novel evidence of the biochemical and physiological responses of plants to VOCs emitted by B. bassiana and 3-methylbutanol (3MB) as the most abundant compound emitted by the fungus.MethodsSorghum plants were exposed to the standard 3MB and VOCs emitted by the fungal strains AS5 and AI2 of B. bassiana isolated from soil and a mycosed insect cadaver, respectively. The accumulation of reactive oxygen species (ROS) such as superoxide anion (O2•¯) and H2O2; quantification of phytohormones such as salicylic acid (SA), jasmonic acid (JA), and indole-3-acetic acid (IAA) and phenolic compounds in leaves (4-coumaric acid and flavonoids); and the expression of genes SbPR-1 and SbCOI1 related to the activation of SA- and JA-signaling defense pathways, respectively, were analyzed.Results and discussionVOCs emitted by B. bassiana and 3MB stimulate plant growth, likely by triggering the production of ROS and IAA. Furthermore, these fungal compounds increased the expression levels of SbPR-1 and SbCOI1 at 2 d and SbCOI1 at 7 d. Consistently, an increase in the content of SA, JA, and phenolic compounds was observed in the inoculated plants.ConclusionVOCs emitted by B. bassiana and 3-MB promote sorghum growth and activate adaptive defense traits. Moreover, VOCs from AS5 triggered a stronger biochemical response in plants than VOCs emitted by AI2. These results suggested that the response of the plant was strain-specific. Finally, 3MB is a fungal compound that may stimulate plant growth and defense.

Trichoderma virens and plant growth-promoting bacteria (PGPB) are well-known agents that promote plant development and control pathogens. This study assessed the compatibility, biocontrol potential, and plant growth promotion of T. virens in combination with four PGPB strains (Pseudomonas fluorescens UM270, Rouxiella badensis SER3, Bacillus velezensis AF12, and Bacillus halotolerans AF23) against Fusarium brachygibbosum and Arabidopsis thaliana. The results showed that single inoculations significantly inhibited the growth of F. brachygibbosum by the 7th day of confrontation. However, co-inoculating T. virens with PGPB exhibited synergistic effects on the inhibition percentages for the consortia Tv + UM270 (48.94%), Tv + AF12 (67.04%), and Tv + SER3 (78.63%). Plant assays demonstrated that most microorganisms enhanced root development and plant height, with UM270 having the strongest beneficial effect. Expression analysis of T. virens effector genes (sm1, tvsep3, and tvhydii1) indicated early induction of tvhydii1 in the condition of Fb + AF12 at day 3, while sm1 was downregulated. No significant changes in the expression of these genes were detected during interaction with A. thaliana and PGPB. These findings demonstrate that T. virens-PGPB can simultaneously promote plant growth and suppress pathogens, with effector genes such as tvhydii1 contributing to these interactions, highlighting their potential for sustainable agriculture.

Global population growth poses major challenges to agricultural systems, demanding more efficient strategies to secure food production. Conventional approaches have relied heavily on chemical inputs; however, their overuse disrupts ecosystems, threatens biodiversity, and undermines human and environmental health. To ensure sustainable productivity, it is essential to explore alternative approaches that leverage microbial functions to enhance plant growth and resilience. Bacteria are among the most abundant soil microorganisms, playing central roles in biogeochemical cycles and plant health. While well-studied phyla such as Pseudomonadota, Actinomycetota, and Bacillota have been widely applied as biofertilizers and biocontrol agents, members of the phylum Bacteroidota remain comparatively understudied despite being consistently abundant in plant-associated microbiomes. This review synthesizes current knowledge on Bacteroidota, highlighting their taxonomy, ecological diversity, contributions to nutrient cycling, and mechanisms that promote plant growth, as well as biotic and abiotic stress tolerance. We also discuss the limitations that hinder their application, particularly challenges in cultivation and isolation, and outline future research directions to harness their potential for sustainable agriculture.

Phospholipase D (PLD) metabolize phospholipids in cell membranes to produce phosphatidic acid (PA), a second messenger involved in activating signaling pathways associated with developmental processes and responses to various environmental stresses. This study investigated the effect of Azospirillum baldaniorum lipopolysaccharides (LPS) on PLD activity and its relationship with the Target of Rapamycin (TOR) signaling pathway during the growth promotion of Arabidopsis thaliana. Treatment with LPS (100 µg/mL) increased PLD activity with 5 min, with a more pronounced effect observed at 30 min. PA content also increased in parallel with PLD activity, reaching its peak at 30 min. LPS failed to promote growth in the xipot1 mutant, which is defective in phosphocholine biosynthesis, a precursor of phosphatidylcoline, the substrate of PLD, and exhibited low PA production. LPS-stimulated PA accumulation was inhibited by 1-butanol, which blocks the PLD-catalyzed transphosphatidylation reaction. The increase in TOR expression induced by LPS treatment was also inhibited by 1-butanol. Exogenous application of various PA species (e.g., di16:0-PA, di18:0-PA, and di18:1-PA) increased TOR expression, with unsaturated PA (di18:1-PA) demonstrating the highest biological potency. LPS treatment further increased the expression of ribosomal genes RPS27B (Small Ribosomal Subunit Protein 27B) and RPL7B (Large Ribosomal Subunit Protein L7B), but not RPS6B (Ribosomal Protein 6S). The expression of the cell cycle reporter CycB1;1::GUS in the root meristem, a process influenced by TOR, was stimulated by the application of different PA species, with di18:1-PA showing the strongest effect. These results highlights the role of PLD activity as a modulator of Arabidopsis TOR signaling in response to A. baldaniorum Sp245 LPS.

A detailed diversity analysis of the prokaryotic and fungal communities in soil impacted by an underground fire located in the Trans-Mexican volcanic belt, Mexico, is described. Microbial diversity data obtained from soils at different depths and temperatures (27 degrees C, 42 degrees C, 50 degrees C and 54 degrees C) were analyzed, and Firmicutes increased in abundance as the temperature augmented, and Proteobacteria mainly decreased in abundance at high temperatures compared to unaffected soils. The fungal phylum Ascomycota was the most abundant, with no significant changes. A clear reduction in the richness of both prokaryotic and eukaryotic operational taxonomic units (OTUs) was observed in the affected soils. At the genus level, Bacillus species were the most abundant among bacteria, while Aspergillus, Penicillium, and Mortierella were dominant fungal genera at higher temperatures. Interestingly, the physicochemical parameters of the affected soils modified organic matter, which was indirectly correlated with the presence of some microbial taxa. Likewise, we obtained 308 soil bacterial isolates from both control and affected soils. Among these, the taxa from the phyla Actinobacteria and Firmicutes demonstrated the highest thermotolerance in the affected soils. Our findings shed light on the impact of underground fires on the structure of microbial communities, favoring an abundance of thermotolerant microbes.

Trichoderma uses different molecules to establish communication during its interactions with other organisms, such as effector proteins. Effectors modulate plant physiology to colonize plant roots or improve Trichoderma's mycoparasitic capacity. In the soil, these fungi can establish relationships with plant growth-promoting bacteria (PGPBs), thus affecting their overall benefits on the plant or its fungal prey, and possibly, the role of effector proteins. The aim of this study was to determine the induction of Trichoderma atroviride gene expression coding for effector proteins during the interaction with different PGPBs, Arabidopsis or the phytopathogen Fusarium brachygibbosum, and to determine whether PGPBs potentiates the beneficial effects of T. atroviride. During the interaction with F. brachygibbosum and PGPBs, the effector coding genes epl1, tatrx2 and tacfem1 increased their expression, especially during the consortia with the bacteria. During the interaction of T. atroviride with the plant and PGPBs, the expression of epl1 and tatrx2 increased, mainly with the consortium formed with Pseudomonas fluorescens UM270, Bacillus velezensis AF12, or B. halotolerans AF23. Additionally, the consortium formed by T. atroviride and R. badensis SER3 stimulated A. thaliana PR1:GUS and LOX2:GUS for SA- and JA-mediated defence responses. Finally, the consortium of T. atroviride with SER3 was better at inhibiting pathogen growth, but the consortium of T. atroviride with UM270 was better at promoting Arabidopsis growth. These results showed that the biocontrol capacity and plant growth-promoting traits of Trichoderma spp. can be potentiated by PGPBs by stimulating its effector functions.

The legume family includes approximately 19,300 species across three large subfamilies, of which Papilionoideae stands out with 13,800 species. Lentils were one of the first crops to be domesticated by humans, approximately 11,000 BP. They are diploid legumes that belong to the Papilionoidea subfamily and are of agricultural importance because of their resistance to drought and the fact that they grow in soil with a pH range of 5.5–9; therefore, they are cultivated in various types of soil, and so they have an important role in sustainable food and feed systems in many countries. In addition to their agricultural importance, lentils are a rich source of protein, carbohydrates, fiber, vitamins, and minerals. They are key to human nutrition since they are an alternative to animal proteins, decreasing meat consumption. Another characteristic of legumes, including lentils, is their ability to form nodules, which gives them a growth advantage in nitrogen-deficient soils because they enable the plant to fix atmospheric nitrogen, thus contributing nitrogen to the soil and facilitating the nutrition of other plants during intercropping. Lentils have also been applied for protection against various human diseases, as well as for phytoremediation, and they also have been applied as environmental bioindicators to identify cytotoxicity. This review addresses the importance of lentils in agriculture and human health.

The actinobacterium Arthrobacter sp. UMCV2 promotes plant growth through the emission of N,N-dimethylhexadecilamine (DMHDA). The Medicago--Sinorhizobium nodulation has been employed to study symbiotic nitrogen fixation by rhizobia in nodulating Fabaceae. Herein, we isolated three Sinorhizobium medicae strains that were used to induce nodules in Medicago truncatula. The co-inoculation of M. truncatula with Arthrobacter sp. strain UMCV2 produced a higher number of effective nodules than inoculation with only Sinorhizobium strains. Similarly, the exposure of inoculated M. truncatula to DMHDA produced a greater number of effective nodules compared to non-exposed plants. Thus, we conclude that Arthrobacter sp. UMCV2 promotes nodulation, and propose that this effect is produced, at least partly, via DMHDA emission. (c) 2024 Asociacion Argentina de Microbiologia. Published by Elsevier Espana, S.L.U. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/bync-nd/4.0/).

Hydrogen peroxide (H2O2) is naturally produced by plant cells during normal development and serves as a messenger that regulates cell metabolism. Despite its importance, the relationship between hydrogen peroxide and the target of rapamycin (TOR) pathway, as well as its impact on cell division, has been poorly analyzed. In this study, we explore the interaction of H2O2 with TOR, a serine/threonine protein kinase that plays a central role in controlling cell growth, size, and metabolism in Arabidopsis thaliana. By applying two concentrations of H2O2 exogenously (0.5 and 1 mM), we could correlate developmental traits, such as primary root growth, lateral root formation, and fresh weight, with the expression of the cell cycle gene CYCB1;1, as well as TOR expression. When assessing the expression of the ribosome biogenesis-related gene RPS27B, an increase of 94.34

Saline soils pose significant challenges to global agricultural productivity, hindering crop growth and efficiency. Despite various mitigation strategies, the issue persists, underscoring the need for innovative and sustainable solutions. One promising approach involves leveraging microorganisms and their plant interactions to reclaim saline soils and bolster crop yields. This review highlights pioneering and recent advancements in utilizing multi-traits Trichoderma and Bacillus species as potent promoters of plant growth and health. It examines the multifaceted impacts of saline stress on plants and microbes, elucidating their physiological and molecular responses. Additionally, it delves into the role of ACC deaminase in mitigating plant ethylene levels by Trichoderma and Bacillus species. Although there are several studies on Trichoderma-Bacillus, much remains to be understood about their synergistic relationships and their potential as auxiliaries in the phytoremediation of saline soils, which is why this work addresses these challenges.

Volatile organic compounds (VOCs) are low molecular weight molecules that tend to evaporate easily at room temperature because of their low boiling points. VOCs are emitted by all organisms; therefore, inter- and intra-kingdom interactions have been established, which are fundamental to the structuring of life on our planet. One of the most studied interactions through VOCs is between microorganism VOCs (mVOCs) and plants, including those of agricultural interest. The mVOC interactions generate various advantages for plants, ranging from promoting growth to the activation of defense pathways triggered by salicylic acid (systemic acquired resistance) and jasmonic acid (induced systemic resistance) to protect them against phytopathogens. Additionally, mVOCs directly inhibit the growth of phytopathogens, thereby providing indirect protection to plants. Among the current agricultural problems is the extensive use of chemicals, such as fertilizers, intended to combat production loss, and pesticides to combat phytopathogen infection. This causes problems in food safety and environmental pollution. Therefore, to overcome this problem, it is important to identify alternatives that do not generate environmental impacts, such as the application of mVOCs. This review addresses the protective effects of mVOCs emitted by microorganisms from different kingdoms and their implications in plant defense pathways.

Plants are at risk of attack by various pathogenic organisms. During pathogenesis, microorganisms produce molecules with conserved structures that are recognized by plants that then initiate a defense response. Plants also experience iron deficiency. To address problems caused by iron deficiency, plants use two strategies focused on iron absorption from the rhizosphere. Strategy I is based on rhizosphere acidification and iron reduction, whereas Strategy II is based on iron chelation. Pathogenic defense and iron uptake are not isolated phenomena: the antimicrobial phenols are produced by the plant during defense, chelate and solubilize iron; therefore, the production and secretion of these molecules also increase in response to iron deficiency. In contrast, phytohormone jasmonic acid and salicylic acid that induce pathogen-resistant genes also modulate the expression of genes related to iron uptake. Iron deficiency also induces the expression of defense-related genes. Therefore, in the present review, we address the cross-talk that exists between the defense mechanisms of both Systemic Resistance and Systemic Acquired Resistance pathways and the response to iron deficiency in plants, with particular emphasis on the regulation genetic expression.

N,N-dimethylhexadecylamine (DMHDA) is a bacterial volatile organic compound that affects plant growth and morphogenesis and is considered a cross-kingdom signal molecule. Its bioactivity involves crosstalk with the cytokinin and jasmonic acid (JA) pathways to control stem cell niches and induce iron deficiency adaptation and plant defense. In this study, through genetic analysis, we show that the DMHDA-JA-Ethylene (ET) relations determine the magnitude of the defensive response mounted during the infestation of Arabidopsis plants by the pathogenic fungus Botrytis cinerea. The Arabidopsis mutants defective in the JA receptor CORONATINE INSENSITIVE 1 (coi1-1) showed a more severe infestation when compared to wild-type plants (Col-0) that were partially restored by DMHDA supplements. Moreover, the oversensitivity manifested by ETHYLENE INSENSITIVE 2 (ein2) by B. cinerea infestation could not be reverted by the volatile, suggesting a role for this gene in DMHDA reinforcement of immunity. Growth of Col-0 plants was inhibited by DMHDA, but ein2 did not. Noteworthy, Arabidopsis seeds treated with DMHDA produced more vigorous plants throughout their life cycle. These data are supportive of a scenario where plant perception of a bacterial volatile influences the resistance to a fungal phytopathogen while modulating plant growth.

Beneficial rhizobacteria such as Arthrobacter agilis and Pseudomonas fluorescens produce N , N -dimethylhexadecylamine (DMHDA), a volatile organic compound that acts as a plant-microorganism signal, inducing bacterial motility and plant defense mechanisms. In the present study, Medicago truncatula seedlings were cultured in vitro and inoculated with the microbial fraction of soil with or without DMHDA, and DNA from Actinobacteria, Firmicutes, and α, β, and γ-proteobacteria were quantified using quantitative polymerase chain reaction to obtain a bacterial community profile of root and shoot endophytic compartments. In seedlings cultured without DMHDA, β-proteobacteria and α-proteobacteria were more abundant in root and shoot endophytic compartments, respectively. However, when seedlings were cultured with DMHDA, the proportion of Actinobacteria and Firmicutes increased in both compartments. These changes were dependent on the dose of DMHDA. We propose that DMHDA modulates the endophytic microbiome by inducing plant immune responses.

Quorum sensing (QS) is a bacterial cell-cell communication system with genetically regulated mechanisms dependent on cell density. Canonical QS systems in gram-negative bacteria possess an autoinducer synthase (LuxI family) and a transcriptional regulator (LuxR family) that respond to an autoinducer molecule. In Gram-positive bacteria, the LuxR transcriptional regulators "solo" (not associated with a LuxI homolog) may play key roles in intracellular communication. Arthrobacter sp. UMCV2 is an actinobacterium that promotes plant growth by emitting the volatile organic compound N, N-dimethylhexadecylamine (DMHDA). This compound induces iron deficiency, defense responses in plants, and swarming motility in Arthrobacter sp. UMCV2. In this study, the draft genome of this bacterium was assembled and compared with the genomes of type strains of the Arthrobacter genus, finding that it does not belong to any previously described species. Genome explorations also revealed the presence of 16 luxR-related genes, but no luxI homologs were discovered. Eleven of these sequences possess the LuxR characteristic DNA-binding domain with a helix-turn-helix motif and were designated as auto-inducer-related regulators (AirR). Four sequences possessed LuxR analogous domains and were designated as auto-inducer analogous regulators (AiaR). When swarming motility was induced with DMHDA, eight airR genes and two aiaR genes were upregulated. These results indicate that the expression of multiple luxR-related genes is induced in actinobacteria, such as Arthrobacter sp. UMCV2, by the action of the bacterial biocompound DMHDA when QS behavior is produced.

The plant microbiomes include root-associated beneficial species, which rely on carbon supplements to survive and exert their diverse attributes. Here, we isolated and identified through 16S rRNA analysis a novel plant growth promoting rhizobacterium belonging to the Bacillus genus ( Bacillus sp. LC390B) from a collection from root isolates of maize plants grown in an alkaline-calcareous soil. The LC390B strain enhanced shoot and root fresh weights and chlorophyll content in leaves upon direct cocultivation with Arabidopsis roots in medium lacking sucrose or supplemented with 0.6% sucrose, and upon transfer to artificial soil led plants to produce more fruits. These effects coincided with faster cell elongation, enhanced primary root growth and higher branching capacity, and increase in local auxin response within lateral root primordia. Mutant analysis indicated that specific elements in the auxin pathway control either primary root elongation or branching in bacterized plants, while most of the probiotic attributes were missing in a double mutant defective on the phytochromes PHYA and PHYB . The bacteria remained viable in interactions with roots up to seven days, supporting its long lasting effects to plants. Our data show that the newly isolated LC390 strain has potential to stimulate the growth of plants and unveil a critical function of specific elements in the auxin and phytochrome signaling network in plant–bacteria interaction.

Dimethylhexadecylamine, a bacterial compound, promoted strawberry achene germination and a long-lasting effect on plant growth; furthermore, it induced necrotrophic pathogen resistance possibly through crosstalk with the jasmonic acid pathway. Dimethylhexadecylamine (DMHDA) is a volatile compound produced by different beneficial plant bacteria. DMHDA induces growth and activates the jasmonic acid (JA) signaling pathway in plants. In this study, we analyzed the effects of synthetic DMHDA on achene germination, as well as the long-term effect on plant growth and plant pathogen resistance in vitro in strawberry plants. Strawberry achenes treated with 32 µM DMHDA showed a three-fold increase in germination rates compared with untreated achenes, and plants from achenes germinated with 64 µM DMHDA grew four times larger than plants from untreated achenes. When plants were cultured in vitro with DMHDA as a continuous stimulus, they produced 40% less shoot growth but showed an up to four-fold increase in crown weight compared with control plants. DHMDA also induced resistance significantly against the necrotrophic pathogenic fungus Botrytis cinerea in strawberry. Our data showed that the bacterial volatile compound DMHDA regulated achene germination and produced a long-lasting effect on plant growth; furthermore, it induced a defense priming response against a necrotrophic pathogen. Crosstalk between DMHDA and the JA and salicylic acid pathways, as a potential mechanisms of action underlying these effects, is also discussed.

The endophytic bacterial diversity of root, stem, and leaf tissues of Mexican husk tomato plants (Physalis ixocarpa) was compared and deciphered, and screened for their plant growth-promoting activity and antagonism against fungal phytopathogens. Total 315 isolates (108 roots, 102 stems, and 105 leaves) were obtained and characterized by 16S ribosomal gene sequencing. The most abundant genera were Bacillus, Microbacterium, Pseudomonas, and Stenotrophomonas. Unique species were found for each tissue analyzed, along with B. thuringiensis, B. toyonensis, Neobacillus drentensis, Paenibacillus castaneae, P. fluorescens, P. poae, and S. maltophilia present throughout the plant. Biodiversity indices did not show significant differences, but root tissues showed the highest abundance of bacterial endophytes. Several isolates showed excellent promotion activities in Physalis ixocarpa seedlings, increasing the length and weight of the root, total biomass, and chlorophyll content. Various isolates also exhibited antagonism against fungal pathogens. Among screened isolates, Neobacillus drentensis CH23 was found in all plant compartments, exhibiting growth-promoting activity and fungal antagonism. Strain CH23 and other endophytes showed the production of indoleacetic acid, siderophores, proteases, and solubilization of phosphates. These results demonstrate that the husk tomato plant endobiome has a high potential as a bioinoculating agent for agriculturally important crops.

N,N-dimethyl-hexadecylamine (DMHDA) is a volatile organic compound (VOC) produced by some plant growth-promoting rhizobacteria (PGPR), which inhibits the growth of pathogenic fungi and induces iron uptake by roots. In this report, through the application of a wide range of concentrations, we found that DMHDA affects Arabidopsis primary root growth and lateral root formation in a dose-dependent manner where 1 and 2 µM promoted root growth and higher (4-32 µM) concentrations repressed growth. Cytokinin-inducible TCS::GFP and ARR5::uidA gene constructs showed an increased expression in columella cells and root meristem, respectively, at 2 µM DMHDA, but their expression domains strongly diminished at growth repressing treatments. To test if either primary root growth promotion or repression could involve members of the cytokinin receptor family, the growth of WT and double mutant combinations cre1-12 ahk2-2, cre1-12 ahk3-3, and ahk2-2 ahk3-3 was tested in control conditions or supplemented with 2 µM or 16 µM DMHDA. Noteworthy, the root growth promotion disappeared in cre1-12 ahk2-2 and ahk2-2 ahk3-3 combinations, whereas all double mutants had higher repression than the WT at high doses. We further show that DMHDA fails to mimic the effects of ethylene in Arabidopsis seedlings grown in darkness that include an exaggerated apical hook, stem and root shortening, and root hair elongation. Our data help unravel how Arabidopsis senses a growth-modulating bacterial volatile through changes in cytokinin responsiveness.

The interaction of plant roots with bacteria is influenced by chemical signaling, where auxins play a critical role. Auxins exert positive or negative influences on the plant traits responsible of root architecture configuration such as root elongation and branching and root hair formation, but how bacteria that modify the plant auxin response promote or repress growth, as well as root structure, remains unknown. Here, we isolated and identified via molecular and electronic microscopy analysis a Micrococcus luteus LS570 strain as a plant growth promoter that halts primary root elongation in Arabidopsis seedlings and strongly triggers root branching and absorptive potential. The root biomass was exacerbated following root contact with bacterial streaks, and this correlated with inducible expression of auxin-related gene markers DR5:GUS and DR5:GFP. Cellular and structural analyses of root growth zones indicated that the bacterium inhibits both cell division and elongation within primary root tips, disrupting apical dominance, and as a consequence differentiation programs at the pericycle and epidermis, respectively, triggers the formation of longer and denser lateral roots and root hairs. Using Arabidopsis mutants defective on auxin signaling elements, our study uncovers a critical role of the auxin response factors ARF7 and ARF19, and canonical auxin receptors in mediating both the primary root and lateral root response to M. luteus LS570. Our report provides very basic information into how actinobacteria interact with plants and direct evidence that the bacterial genus Micrococcus influences the cellular and physiological plant programs ultimately responsible of biomass partitioning.