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

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

Data from: Mutualism effectiveness and vertical transmission of symbiotic fungal endophytes in response to host genetic background

Certain species of the Pooideae subfamily develop stress tolerance and herbivory resistance through symbiosis with vertically-transmitted, asexual fungi. This symbiosis is specific, and genetic factors modulate compatibility between partners. Although gene flow is clearly a fitness trait in allogamous grasses, since it injects hybrid vigor and raw material for evolution, it could reduce compatibility and thus, mutualism effectiveness. To explore the importance of host genetic background in modulating the performance of symbiosis, Lolium multiflorum plants, infected and non-infected with Neotyphodium occultans, were crossed with genetically distant plants of isolines (susceptible and resistant to diclofop-methyl herbicide) bred from two cultivars, and exposed to stress. The endophyte improved seedling survival in genotypes susceptible to herbicide, while it had a negative effect on one of the genetically resistant crosses. Mutualism provided resistance to herbivory independently of the host genotype, but this effect vanished under stress. While no endophyte effect was observed on host reproductive success, it was increased by inter-population plant crosses. Neither gene flow nor herbicide had an important impact on endophyte transmission. Host fitness improvements due to gene flow do not appear to result in direct conflict with mutualism while this seems to be an important mechanism for the ecological and contemporary evolution of the symbiotum

Archiving data

Each sheet of the Excel file contains each measured variable (survival to herbicide, aphid herbivory, plant yield and endophyte transmission) in the two experiments. The logic is easy to understand since the nomenclature is the same used in the article

Can Aphid Herbivory Induce Intergenerational Effects of Endophyte-conferred Resistance in Grasses?

Plants have evolved mechanisms to survive herbivory. One such mechanism is the induction of defences upon attack that can operate intergenerationally. Cool-season grasses (sub-family Pooideae) obtain defences via symbiosis with vertically transmitted fungal endophytes (genus Epichloë) and can also show inducible responses. However, it is unknown whether these herbivore-induced responses can have intergenerational effects. We hypothesized that herbivory by aphids on maternal plants induces the intergenerational accumulation of endophyte-derived defensive alkaloids and resistance intensification in the progeny. We subjected mother plants symbiotic or not with Epichloë occultans, a species known for its production of anti-insect alkaloids known as lolines, to the aphid Rhopalosiphum padi. Then, we evaluated the progeny of these plants in terms of loline alkaloid concentration, resistance level (through herbivore performance), and shoot biomass. Herbivory on mother plants did not increase the concentration of lolines in seeds but it tended to affect loline concentration in progeny plants. There was an overall herbivore-induced intergenerational effect increasing the endophyte-conferred defence and resistance. Symbiotic plants were more resistant to aphids and had higher shoot biomass than their non-symbiotic counterparts. Since maternal herbivory did not affect the loline concentrations in seeds, the greater resistance of the progeny could have resulted from an inherited mechanism of epigenetic regulation. It would be interesting to elucidate the origin of this regulation since it could come from the host or the fungal symbiont. Thus, endophyte-driven differential fitness between symbiotic and non-symbiotic plants might be higher as generations pass on in presence of herbivores.Fil: Bubica Bustos, Ludmila Micaela. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; ArgentinaFil: Ueno, Andrea Celeste. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; ArgentinaFil: Biganzoli, Fernando. Universidad de Talca; ChileFil: Card, Stuart D.. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Métodos Cuantitativos y Sistemas de Información; ArgentinaFil: Mace, Wade J.. No especifíca;Fil: Martínez Ghersa, María A.. No especifíca;Fil: Gundel, Pedro Emilio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentin

The negative effect of a vertically-transmitted fungal endophyte on seed longevity is stronger than that of ozone transgenerational effect

Seed morphology underpins many critical biological and ecological processes, such as seed dormancy and germination, dispersal, and persistence. It is also a valuable taxonomic trait that can provide information about plant evolution and adaptations to different ecological niches. This study characterised and compared various seed morphological traits, i.e., seed and pod shape, seed colour and size, embryo size, and air volume for six orchid species; and explored whether taxonomy, biogeographical origin, or growth habit are important determinants of seed morphology. We investigated this on two tropical epiphytic orchid species from Indonesia (Dendrobium strebloceras and D. lineale), and four temperate species from New Zealand, terrestrial Gastrodia cunnninghamii, Pterostylis banksii and Thelymitra nervosa, and epiphytic D. cunninghamii. Our results show some similarities among related species in their pod shape and colour, and seed colouration. All the species studied have scobiform or fusiform seeds and prolate-spheroid embryos. Specifically, D. strebloceras, G. cunninghamii, and P. banksii have an elongated seed shape, while T. nervosa has truncated seeds. Interestingly, we observed high variability in the micro-morphological seed characteristics of these orchid species, unrelated to their taxonomy, biogeographical origin, or growth habit, suggesting different ecological adaptations possibly reflecting their modes of dispersal