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Plants host numerous endophytic microbes which promote plant performance, in particular under stress. A new endophytic fungus was isolated from the leaves of a deciduous wood tree Leucas aspera. Morphological inspection and multilocus phylogeny identified the fungus as a new Trichoderma strain. If applied to Arabidopsis thaliana and Nicotiana attenuata , it mainly colonizes their roots and strongly promotes initial growth of the plants on soil. The fungus grows on high NaCl or mannitol concentrations, and shows predatory capability on the pathogenic fungus Alternaria brassicicola . Colonized Arabidopsis plants tolerate higher salt stress and show lower A. brassicicola spread in roots and shoots, while arbuscular mycorrhiza formation in N. attenuata is not affected by the Trichoderma strain. These beneficial features of the novel Trichoderma strain are important prerequisites for agricultural applications.

Here, we used the RNA-seq approach to understand better the effect of G. diazotrophicus PAL5 on the transcriptome of shoot and root tissues of Arabidopsis thaliana. G. diazotrophicus colonized A. thaliana roots and promoted growth, increasing leaf area and biomass.

Improvement and year-to-year stabilization of biomass yields are primary objectives for the development of a low-input switchgrass feedstock production system using microbial endophytes. An earlier investigation of the effect of Burkholderia phytofirmans strain PsJN on switchgrass germplasm demonstrated differential responses between genotypes. PsJN inoculation of cv. Alamo (lowland ecotype) increased the plant root system, shoot length, and biomass yields, whereas it had no beneficial effect on cv. Cave-in-Rock (upland ecotype). To understand the gene networks governing plant growth promotion responses triggered by PsJN, the gene expression profiles were analysed in these two hosts, following seedling inoculation. The Affymetrix platform switchgrass expressed sequence tag (EST) microarray chip representing 122 972 probe sets, developed by the DOE BioEnergy Science Center, was employed to assess transcript abundance at 0.5, 2, 4, and 8 DAI (days after PsJN inoculation). Approximately 20 000 switchgrass probe sets showed significant responses in either cultivar. Switchgrass identifiers were used to map 19 421 genes in MapMan software. There were apparent differences in gene expression profiling between responsive and non-responsive cultivars after PsJN inoculation. Overall, there were 14 984 and 9691 genes affected by PsJN inoculation in Alamo and Cave-in-Rock, respectively. Of these, 394 are annotated as pathogenesis-related genes. In the responsive cv. Alamo, 68 pathogenesis-related genes were affected, compared with only 10 in the non-responsive cv. Cave-in-Rock. At the very early stage at 0.5 DAI, both cultivars exhibited similar recognition and defence responses, such as genes in signalling and proteolysis, after which the defence reaction in the responsive cv. Alamo became weaker while it was sustained in non-responsive cv. Cave-in-Rock.

Endophytes can be a promising alternative for sustainable agronomic practices. In this study, we report for the first time a root-colonizing fungal strain (Sl27) of the genus Leptobacillium as a tomato (Solanum lycopersicum) endophyte, with no clear homology to any known species. Performed analyses and assays, including morphological and physiological characterization of the fungal isolate, provided insights into the ecological niche and potential agronomical and industrial applications of the fungal isolate. The ability of Sl27 to establish a symbiotic relationship with the host plant was assessed through experiments under controlled conditions in the growth chamber and greenhouse. Seed- inoculation showed no detrimental effects in the three tomato genotypes studied (TH-30, ADX2, MO-10). The influence of Sl27 on growth parameters of the host plant was dependent on the tomato genotype, with TH-30 showing the most prominent improved phenotype. Moreover, chlorophyll and lycopene content in fruits were enhanced. These findings provide a basis for further studies on the potential application of this new isolate for improving crop performance.

Background The study aimed at enumerating, identifying and categorizing the endophytic cultivable bacterial community in selected salad vegetables (carrot, cucumber, tomato and onion). Vegetable samples were collected from markets of two vegetable hot spot growing areas, during two different crop harvest seasons. Crude and diluted vegetable extracts were plated and the population of endophytic bacteria was assessed based on morphologically distinguishable colonies. The bacterial isolates were identified by growth in selective media, biochemical tests and 16S rRNA gene sequencing. Results The endophytic population was found to be comparably higher in cucumber and tomato in both of the sampling locations, whereas lower in carrot and onion. Bacterial isolates belonged to 5 classes covering 46 distinct species belonging to 19 genera. Human opportunistic pathogens were predominant in carrot and onion, whereas plant beneficial bacteria dominated in cucumber and tomato. Out of the 104 isolates, 16.25% are human pathogens and 26.5% are human opportunistic pathogens. Conclusions Existence of a high population of plant beneficial bacteria was found to have suppressed the population of plant and human pathogens. There is a greater potential to study the native endophytic plant beneficial bacteria for developing them as biocontrol agents against human pathogens that are harboured by plants.

Ozone is an increasing tropospheric contaminant of climate change. Exposure to ozone may affect the symbiotic relationship between plants and beneficial microorganisms. In particular, the herbivore resistance mechanism conferred by fungal endophytes (defensive mutualism) may be affected, as any of the ozone‐triggered effects (such as elicitation of defence mechanisms against biotrophic fungi or oxidative stress in the apoplastic space) may target the symbiont. Symbiotic and non‐symbiotic Lolium multiflorum plants were exposed to ozone for two consecutive days (2 h per day), after which half were infested with 10 aphids (Rhopalosiphum padi). We measured variables related to performance of plants, the endophyte symbiont (alkaloids) and the herbivores. Aphid populations were smaller on symbiotic plants than in non‐symbiotic plants in low‐ozone conditions. However, this difference disappeared in exposed plants to high‐ozone conditions. Under low‐ozone conditions, structure of aphid populations on endophyte‐symbiotic plants was characterized by a low number of nymphs and a high number of adults. This pattern was not observed with high‐ozone exposure. Level of fungal alkaloids (lolines) was not affected by either ozone or herbivory. Results indicate that ozone impairs the grass‐endophyte symbiosis without affecting production of alkaloids generally linked with aphids' response to endophyte presence. Since neither plant biomass nor alkaloid level were affected by ozone, other ozone‐mediated mechanisms at molecular or biochemical level may underlie plant‐herbivore interaction mediated by fungal endophytes. Thus, the mechanism behind this effect must be determined in future experiments.

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

The endophytes associated with the Zingiberaceae family have demonstrated remarkable potential in various biological activities through their bioactive compounds that are useful for both medical and agricultural purposes. Additionally, isolated secondary metabolites from symbiotic microbes associated with this family of plants have shown promising results in various biological activities such as antifungal, anticancer, antidiabetic, anti-inflammatory, and antibacterial. This review focuses on the bioactive metabolites of Zingiberaceae endophytes with their potential biological activities against different pathogens as well as the production of phytohormones that promote plant growth. Furthermore, bibliometric analysis revealed the current key trends and collaborative works in this field. Additionally, the bibliometric analysis also explored a total of 75 relevant publications from the Scopus database that India is the most contributing country in this field with 38.7% of the total reported research work. The bibliometric approach helps uncover new research gaps by identifying emerging trends, underexplored topics, and collaborative networks, providing insights into areas that require further investigation and development. Notably, Streptomyces spp. have been commonly reported as potent endophytes, generating bioactive substances such as Vanillin and Resacetophenone with strong antibacterial activities. Significant knowledge gaps still exist, and with evolving therapeutic potential, this could offer a wide opportunity for new studies to emerge.

1. The most studied mechanism of protection against herbivores in grasses associated with Epichloë fungal endophytes has been the fungal production of alkaloids. However, the contribution of the plant immune response on the level of resistance to herbivores in symbiotic grasses has been poorly explored. We studied the relationship between the plant hormone, jasmonic acid (JA) and Epichloë fungal endophytes on herbivore defences in symbiotic grasses. We hypothesized that an exogenous application of methyl jasmonate (MeJA), an activator of the plant JA defence response, would increase the level of resistance of endophyte-symbiotic and non-symbiotic plants to a chewing insect. As Epichloë endophytes produce alkaloids, an enhancement of the JA defence would complement the resistance given by these alkaloids. 2. Lolium multiflorum plants symbiotic and non-symbiotic with the endophyte Epichloë occultans were subjected to an exogenous application of MeJA followed by a challenge with the generalist chewing insect Spodoptera frugiperda. We measured the level of plant resistance to chewing insects, and the defences conferred by host plants and fungal endophytes. 3. Symbiotic plants were more resistant to S. frugiperda than their non-symbiotic counterparts. However, despite the fact that the concentration of JA significantly increased in all plants exposure to MeJA, neither endophyte-symbiotic nor nonsymbiotic plants showed an enhanced resistance to insects. Unexpectedly, the exposure of endophyte-symbiotic plants to MeJA led to a reduction in the concentration of loline alkaloids (i.e. N-formyllolines and N-acetylnorlolines), consequently decreasing the level of plant resistance to the herbivore. 4. Synthesis. Our results suggest that, rather than complementing the alkaloid-based defence, the jasmonic acid hormone weakens the anti-herbivore mechanism conferred by Epichloë endophytes. The present study highlights that the interaction between the jasmonic acid hormone and the presence of leaf fungal endophytes can be of importance for the effectiveness of the anti-herbivore defences of symbiotic plants.

Background and aims Plant seeds are emerging micro–habitats, whose importance as reservoir and vector of beneficial microbes just begins to be recognized. Here we aimed to characterize the bacterial microbiota of the Anadenanthera colubrina seed endosphere, with special focus to beneficial traits and to the colonization pattern. Methods Cultivation–dependent (isolation from surface–sterilized seeds) and cultivation–independent (pyrosequencing of 16S rRNA gene from metagenomic seed DNA) analyses, functional tests and microscopical investigations (fluorescence in situ hybridization coupled with confocal laser scanning microscopy (FISH-CLSM) were performed. Results We isolated several Methylobacterium and Staphylococcus spp., exhibiting both plant growth promotion and antimicrobial activities. The two taxonomic groups showed complementary traits, which supports a functional selection. Both genera were detected also by pyrosequencing, together with further taxa. The genera Friedmaniella , Bifidobacterium, Delftia , Anaerococcus and Actinomyces appeared here for the first time as seed endophytes. We detected bacterial cells and micro–colonies in seed cryosections by FISH-CLSM. Alphaproteobacteria, Firmicutes and other bacteria colonized intercellular spaces of the parenchyma and associated to transport vessels. Conclusions This work sheds light onto the diversity, functions and colonization pattern of the Anadenanthera colubrina seed endophytes, and strongly suggest a role as beneficial partners for seed-associated microbiota.