<i>Achnatherum inebrians</i> Bacterial Communities Associated with <i>Epichloë gansuensis</i> Endophyte Infection Under Low-Concentration Urea Treatment: Links to Plant Growth and Root Metabolite
Despite chemical exchange often serving as the first step in plant–microbe interactions, the specialized chemical metabolites produced by grass–<i>Epichloë</i> endophyte symbiosis as mediators of host growth, nutrient acquisition, and modulators of the rhizosphere community under low-nit...
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| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2025-06-01
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| Series: | Microorganisms |
| Subjects: | |
| Online Access: | https://www.mdpi.com/2076-2607/13/7/1493 |
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| Summary: | Despite chemical exchange often serving as the first step in plant–microbe interactions, the specialized chemical metabolites produced by grass–<i>Epichloë</i> endophyte symbiosis as mediators of host growth, nutrient acquisition, and modulators of the rhizosphere community under low-nitrogen conditions are areas lacking in knowledge. In this study, we investigated the plant growth-promoting effects of the <i>Epichloë</i> endophyte strain and identified the growth of the <i>Epichloë</i> strain under different types of nitrogen source treatments. In addition to the in vitro test, we evaluated growth performance for <i>Epichloë</i> endophyte–infected plants (E+) and <i>Epichloë</i> endophyte–free plants (E−) in a pot trial under 0.01 mol/L urea treatment. Seedlings from E+ and E− groups were collected to analyze the plant bacterial microbiome and root metabolites. The <i>E. gansuensis</i> endophyte strain was found not to produce indoleacetic acid (IAA), pectinase, or contain ferritin. The nitrogenase gene, essential for nitrogen fixation, was also absent. These results suggest that <i>E. gansuensis</i> endophyte strains themselves do not contain attributes to promote plant growth. Concerning N fertilization, it was observed an increase in the colony diameter of <i>E. gansuensis</i> strain was observed only in the NO<sub>3</sub><sup>−</sup>-N (NN) treatment, while inhibition was observed in the urea-N (UN) treatment. <i>E. gansuensis</i> endophyte symbiosis significantly increased tiller number and plant dry weight. Overall, our results suggest that the E+ plants had more root forks and greater average root diameter compared to E− plants under the UN treatment. In a pot experiment using UN, data from 16S rRNA amplicon sequencing revealed that <i>E. gansuensis</i> endophyte infection significantly altered the bacterial community composition in shoot and root, and significantly increased Shannon (<i>p</i> < 0.001) and Chao 1 (<i>p</i> < 0.01) indexes. The relative abundance of Acidobacteriota, Actinomycetota, Cyanobacteriota, Fibrobacterota, Myxococcota, and Patescibacteria in the shoot, and Cyanobacteriota, Pseudomonadota, and Verrucomicrobiota in the root were significantly increased by <i>E. gansuensis</i> endophyte infection. Similarly, <i>E. gansuensis</i> endophyte symbiosis shifted the metabolite composition of the host plants, with the E+ plants showing a higher number of metabolites than the E− plants. In addition, co-metabolism network analysis revealed that the positive relevance between exudates and microorganisms in the root of the E+ plants is higher than that of the E− plants. These findings provide valuable insights into the knowledge of the effects of the symbiotic relationship between host plants and <i>Epichloë</i> endophyte on interspecific interactions of plant microbiome, beneficial for harnessing endophytic symbiosis, promoting plant growth. |
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| ISSN: | 2076-2607 |