Epichloe Endophytes Alter Inducible Indirect Defences in Host Grasses

Epichloe endophytes are common symbionts living asymptomatically in pooid grasses and may provide chemical defences against herbivorous insects. While the mechanisms underlying these fungal defences have been well studied, it remains unknown whether endophyte presence affects the host's own defences. We addressed this issue by examining variation in the impact of Epichloe on constitutive and herbivore-induced emissions of volatile organic compounds (VOC), a well-known indirect plant defence, between two grass species, Schedonorus phoenix (ex. Festuca arundinacea; tall fescue) and Festuca pratensis (meadow fescue). We found that feeding by a generalist aphid species, Rhopalosiphum padi, induced VOC emissions by uninfected plants of both grass species but to varying extents, while mechanical wounding failed to do so in both species after one day of damage. Interestingly, regardless of damage treatment, Epichloe uncinata-infected F. pratensis emitted significantly lower quantities of VOCs than their uninfected counterparts. In contrast, Epichloe coenophiala-infected S. phoenix did not differ from their uninfected counterparts in constitutive VOC emissions but tended to increase VOC emissions under intense aphid feeding. A multivariate analysis showed that endophyte status imposed stronger differences in VOC profiles of F. pratensis than damage treatment, while the reverse was true for S. phoenix. Additionally, both endophytes inhibited R. padi population growth as measured by aphid dry biomass, with the inhibition appearing greater in E. uncinata-infected F. pratensis. Our results suggest, not only that Epichloe endophytes may play important roles in mediating host VOC responses to herbivory, but also that the magnitude and direction of such responses may vary with the identity of the Epichloe-grass symbiosis. Whether Epichloe-mediated host VOC responses will eventually translate into effects on higher trophic levels merits future investigation.</p

Mutualism effectiveness and vertical transmission of symbiotic fungal endophytes in response to host genetic backround

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Occurrence of Alkaloids in Grass Seeds Symbiotic With Vertically-Transmitted \u3cem\u3eEpichloë\u3c/em\u3e Fungal Endophytes and Its Relationship With Antioxidants

Host organisms can acquire new functional traits through symbiosis. Seed-transmitted Epichloë fungal endophytes are known to protect host plants against herbivores and increase tolerance to abiotic stresses by alkaloids and antioxidants, respectively (currencies of mutualism). Whereas, alkaloids are fungal products with demonstrated effects at plant vegetative stage, few studies have focused on alkaloids in seeds. We assessed the occurrence of fungal alkaloids and determined their concentrations in seeds of two host grasses, Festuca rubra and Lolium multiflorum. Then, we sought for a relationship with the antioxidants tocochromanols and glutathione, which are involved in the control of oxidative stress. Different alkaloids were detected depending on the species and plant genotype. Most notably, loline alkaloids were not detected in F. rubra seeds, whereas ergovaline and peramine were absent in L. multiflorum. In F. rubra, ergovaline concentration was dependent on the maternal line in interaction with the production year, diminishing in seeds after 1 year of storage. The exposure of L. multiflorum plants to ozone had no effect on the seed concentration of lolines. There was a significant positive relationship between the concentrations of ergovaline and tocochromanols in both species, and between ergovaline concentration and EGSSG/2GSH (glutathione half-cell reduction potential) in RAB maternal line of F. rubra. These results suggest that alkaloid and antioxidants have a close association in seeds of host grasses, and that the alkaloid bioactivity could be related with the antioxidant capacity to control stress. This has important implications for the ecology of partner species, thus supporting its consideration for further research

Geographic Variation in Festuca rubra L. Ploidy Levels and Systemic Fungal Endophyte Frequencies

Polyploidy and symbiotic Epichloe fungal endophytes are common and heritable characteristics that can facilitate environmental range expansion in grasses. Here we examined geographic patterns of polyploidy and the frequency of fungal endophyte colonized plants in 29 Festuca rubra L. populations from eight geographic sites across latitudes from Spain to northernmost Finland and Greenland. Ploidy seemed to be positively and negatively correlated with latitude and productivity, respectively. However, the correlations were nonlinear; 84% of the plants were hexaploids (2n = 6x = 42), and the positive correlation between ploidy level and latitude is the result of only four populations skewing the data. In the southern-most end of the gradient 86% of the plants were tetraploids (2n = 4x = 28), whereas in the northernmost end of the gradient one population had only octoploid plants (2n = 8x = 56). Endophytes were detected in 22 out of the 29 populations. Endophyte frequencies varied among geographic sites, and populations and habitats within geographic sites irrespective of ploidy, latitude or productivity. The highest overall endophyte frequencies were found in the southernmost end of the gradient, Spain, where 69% of plants harbored endophytes. In northern Finland, endophytes were detected in 30% of grasses but endophyte frequencies varied among populations from 0% to 75%, being higher in meadows compared to riverbanks. The endophytes were detected in 36%, 30% and 27% of the plants in Faroe Islands, Iceland and Switzerland, respectively. Practically all examined plants collected from southern Finland and Greenland were endophyte-free, whereas in other geographic sites endophyte frequencies were highly variable among populations. Common to all populations with high endophyte frequencies is heavy vertebrate grazing. We propose that the detected endophyte frequencies and ploidy levels mirror past distribution history of F. rubra after the last glaciation period, and local adaptations to past or prevailing selection forces such as vertebrate grazing.Peer reviewe

Occurrence of Alkaloids in Grass Seeds Symbiotic With Vertically-Transmitted Epichloë Fungal Endophytes and Its Relationship With Antioxidants

Host organisms can acquire new functional traits through symbiosis. Seed-transmitted Epichloë fungal endophytes are known to protect host plants against herbivores and increase tolerance to abiotic stresses by alkaloids and antioxidants, respectively (currencies of mutualism). Whereas, alkaloids are fungal products with demonstrated effects at plant vegetative stage, few studies have focused on alkaloids in seeds. We assessed the occurrence of fungal alkaloids and determined their concentrations in seeds of two host grasses, Festuca rubra and Lolium multiflorum. Then, we sought for a relationship with the antioxidants tocochromanols and glutathione, which are involved in the control of oxidative stress. Different alkaloids were detected depending on the species and plant genotype. Most notably, loline alkaloids were not detected in F. rubra seeds, whereas ergovaline and peramine were absent in L. multiflorum. In F. rubra, ergovaline concentration was dependent on the maternal line in interaction with the production year, diminishing in seeds after 1 year of storage. The exposure of L. multiflorum plants to ozone had no effect on the seed concentration of lolines. There was a significant positive relationship between the concentrations of ergovaline and tocochromanols in both species, and between ergovaline concentration and EGSSG/2GSH (glutathione half-cell reduction potential) in RAB maternal line of F. rubra. These results suggest that alkaloid and antioxidants have a close association in seeds of host grasses, and that the alkaloid bioactivity could be related with the antioxidant capacity to control stress. This has important implications for the ecology of partner species, thus supporting its consideration for further research

Global urban environmental change drives adaptation in white clover

Urbanization transforms environments in ways that alter biological evolution. We examined whether urban environmental change drives parallel evolution by sampling 110,019 white clover plants from 6169 populations in 160 cities globally. Plants were assayed for a Mendelian antiherbivore defense that also affects tolerance to abiotic stressors. Urban-rural gradients were associated with the evolution of clines in defense in 47% of cities throughout the world. Variation in the strength of clines was explained by environmental changes in drought stress and vegetation cover that varied among cities. Sequencing 2074 genomes from 26 cities revealed that the evolution of urban-rural clines was best explained by adaptive evolution, but the degree of parallel adaptation varied among cities. Our results demonstrate that urbanization leads to adaptation at a global scale

Non-systemic fungal endophytes in Festuca rubra plants infected by Epichloë festucae in subarctic habitats

8 páginas, 2 tablas, 2 figuras. -- The final publication is available at www.springerlink.comEpichloë festucae is an endophytic fungus that infects systemically the aerial tissues of the host grass Festuca rubra. This fungus is transmitted vertically from the mother plant to seeds. Hypothetically, the presence of E. festucae could affect the infection of a plant by other fungal species. This could occur if E. festucae metabolites produced in planta interfere negatively with other fungal infections; or alternatively, if the modulation of plant defenses by the endophyte favour further fungal infections. We have analyzed the presence of culturable non-systemic endophytes in plants of F. rubra infected (E+) and not infected (E-) by E. festucae in two subarctic habitats, meadows and riverbanks in Northern Finland. The observed non-systemic endophyte infection frequencies were similar among E+ and E- plants from riverbanks, and E+ plants from meadows. In contrast to these, the infection frequency was significantly lower in E- plants from meadows. This result suggests that the presence of E. festucae is not a main factor determining the presence of non-systemic endophytes in plants. Instead, plant genetic characteristics related to compatibility with E. festucae and other endophytes in the more stable meadow populations might play a role in these fungus-fungus-plant interactions. As a result of the survey, 18 different taxa of non-systemic endophytes were identified in plants of F. rubra. All were ascomycetes except for one basidiomycete. Three endophytic taxa could not be ascribed to a genus, but sequence data indicated that they were conspecific with other unidentified endophytes that have been isolated in cold biomes at different locations.The research leading to these results has received funding from INTERACT (grant agreement No. 262693) under the European Community's Seventh Framework Programme, from Academy of Finland (Project No. 137909), and Spanish Government (Project AGL2011-22783)Peer reviewe

Editorial: Molecular and biochemical effects exerted by the interaction of symbiotic microorganisms with plants to improve their response to environmental stresses

3 Pág.PR was funded by Agencia Nacional de Investigación y Desarrollo (ANID, Chile) (REDES #190078, FONDECYT #1211057, and ANILLO #ATE220014). PG was funded by Agencia Nacional de Investigación y Desarrollo (ANID, Chile) (FONDECYT #1210908). SP obtained financial support from the Spanish Ministry of Science and Innovation (MCIN, Spain) (grant PID2020-119441RB-I00).Peer reviewe