Serendipita (=Piriformospora) indica is a fungal endophytic symbiont with the capabilities to enhance plant growth and confer resistance to different stresses. However, the application of this fungus in the field has led to inconsistent results, perhaps due to antagonism with other microbes. Here, we studied the impact of individual bacterial isolates from the endophytic bacterial community on the in vitro growth of S. indica. We further analyzed how combinations of bacteria and S. indica influence plant growth and protection against the phytopathogens Fusarium oxysporum and Rhizoctonia solani. Bacterial strains of the genera Bacillus, Enterobacter and Burkholderia negatively affected S. indica growth on plates, whereas Mycolicibacterium, Rhizobium, Paenibacillus strains and several other bacteria from different taxa stimulated fungal growth. To further explore the potential of bacteria positively interacting with S. indica, four of the most promising strains belonging to the genus Mycolicibacterium were selected for further experiments. Some dual inoculations of S. indica and Mycolicibacterium strains boosted the beneficial effects triggered by S. indica, further enhancing the growth of tomato plants, and alleviating the symptoms caused by the phytopathogens F. oxysporum and R. solani. However, some combinations of S. indica and bacteria were less effective than individual inoculations. By analyzing the genomes of the Mycolicibacterium strains, we revealed that these bacteria encode several genes predicted to be involved in the stimulation of S. indica growth, plant development and tolerance to abiotic and biotic stresses. Particularly, a high number of genes related to vitamin and nitrogen metabolism were detected. Taking into consideration multiple interactions on and inside plants, we showed in this study that some bacterial strains may induce beneficial effects on S. indica and could have an outstanding influence on the plant-fungus symbiosis.
Aims Plants host communities of fungal and bacterial endophytes, establishing a complex network of multipartite interactions, but the mechanisms whereby they interact are poorly understood. Some fungi, such as the beneficial mycorrhiza-like fungus Serendipita (=Piriformospora) indica, can be helped by bacteria for establishment, survival and colonization. Although this fungus harbors a Rhizobium as an endofungal bacterium, we hypothesized that other bacteria might also establish associations with the fungus and combining S. indica with bacteria might enhance plant growth and health. Methods The interactions among S. indica and four e n d o p h y t i c P r o t e o b a c t e r i a b e l o n g i n g t o Methylobacterium, Tardiphaga, Rhodanobacter and Trinickia spp. were characterized in vitro and for their effect on tomato growth and biocontrol of Fusarium oxysporum and Rhizoctonia solani. Possible mechanisms behind these interactions were described based on genome and microscopic analyses, using fungal and bacterial strains tagged with fluorescent markers. Results All bacteria stimulated S. indica growth in vitro. Moreover, several of the bacteria stimulated growth of tomato plants, but co-inoculations with S. indica and bacteria did not perform better than single inoculations. Contrarily, combinations of S. indica and bacteria significantly reduced disease progression of fungal pathogens. These microbes seem to cooperate in the process of root colonization for instance by increasing fungal sporulation and hyphae expansion, showing multipartite interaction between microbes and plants. Interestingly, the strain of Trinickia internally colonizes spores of S. indica as an endofungal bacterium during in vitro-co-culturing, suggesting further that the fungus might acquire formerly unrecognized genera of bacteria and genome analysis of the bacteria revealed many genes potentially involved in fungal and plant growth stimulation, biocontrol and root colonization, highlighting putative mechanisms of plantfungal-bacterial interaction. Conclusions Our study represents an important step towards unraveling the complex interactions among plants, S. indica, endophytic bacteria and fungal pathogens, and indicates that adding bacteria to fungal inoculum could have a remarkable impact on the plantS. indica symbiosis.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.