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Background and Aims In the subfamily Poöideae (Poaceae), certain grass species possess anti-herbivore alkaloids synthesized by fungal endophytes that belong to the genus Epichloë (Clavicipitaceae). The protective role of these symbiotic endophytes can vary, depending on alkaloid concentrations within specific plant–endophyte associations and plant parts. Methods We conducted a literature review to identify articles containing alkaloid concentration data for various plant parts in six important pasture species, Lolium arundinaceum , Lolium perenne , Lolium pratense , Lolium multiflorum | Lolium rigidum and Festuca rubra , associated with their common endophytes. We considered the alkaloids lolines (1-aminopyrrolizidines), peramine (pyrrolopyrazines), ergovaline (ergot alkaloids) and lolitrem B (indole-diterpenes). While all these alkaloids have shown bioactivity against insect herbivores, ergovaline and lolitrem B are harmful for mammals. Key Results Loline alkaloid levels were higher in the perennial grasses L. pratense and L. arundinaceum compared to the annual species L. multiflorum and L. rigidum , and higher in reproductive tissues than in vegetative structures. This is probably due to the greater biomass accumulation in perennial species that can result in higher endophyte mycelial biomass. Peramine concentrations were higher in L. perenne than in L. arundinaceum and not affected by plant part. This can be attributed to the high within-plant mobility of peramine. Ergovaline and lolitrem B, both hydrophobic compounds, were associated with plant parts where fungal mycelium is usually present, and their concentrations were higher in plant reproductive tissues. Only loline alkaloid data were sufficient for below-ground tissue analyses and concentrations were lower than in above-ground parts. Conclusions Our study provides a comprehensive synthesis of fungal alkaloid variation across host grasses and plant parts, essential for understanding the endophyte-conferred defence extent. The patterns can be understood by considering endophyte growth within the plant and alkaloid mobility. Our study identifies research gaps, including the limited documentation of alkaloid presence in roots and the need to investigate the influence of different environmental conditions. [ABSTRACT FROM AUTHOR]

Ground‐level ozone is a global air pollutant with high toxicity and represents a threat to plants and microorganisms. Although beneficial microorganisms can improve host performance, their role in connecting environmentally induced maternal plant phenotypes to progeny (transgenerational effects [TGE]) is unknown. We evaluated fungal endophyte‐mediated consequences of maternal plant exposure to ozone on performance of the progeny under contrasting scenarios of the same factor (high and low) at two stages: seedling and young plant. With no variation in biomass, maternal ozone‐induced oxidative damage in the progeny that was lower in endophyte‐symbiotic plants. This correlated with an endophyte‐mediated higher concentration of proline, a defence compound associated with stress control. Interestingly, ozone‐induced TGE was not associated with reductions in plant survival. On the contrary, there was an overall positive effect on seedling survival in the presence of endophytes. The positive effect of maternal ozone increasing young plant survival was irrespective of symbiosis and only expressed under high ozone condition. Our study shows that hereditary microorganisms can modulate the capacity of plants to transgenerationally adjust progeny phenotype to atmospheric change. Ozone induced positive transgenerational effects (TGE) by increasing plant survival. It depended on fungal endophytes symbiosis, progeny size, and current ozone condition. Endophytes were determinant for seedlings, while current ozone allowed TGE to express in young plants. Our results give insights on the role of seed‐borne fungi into environmentally induced transgenerational responses of plants. [ABSTRACT FROM AUTHOR]

Our hypothesis is that I Epichloë i endophytes may uncouple the growth-defence trade-off by simultaneously inducing plant growth-related hormones and producing defence compounds (alkaloids) that circumvent the need for host defence-related hormones (Fig. As a final note, it is important to remark that we put forward that endophytes I can i eliminate the growth-defence trade-off, proving our point with I Epichloë i endophytes but acknowledging that not all endophytes would possess the ability to decouple the trade-off. Keywords: alkaloids; endophytes; growth-defence trade-off; phytohormones; symbiosis EN alkaloids endophytes growth-defence trade-off phytohormones symbiosis 388 390 3 06/20/22 20220715 NES 220715 Acknowledgements We thank Víctor M. Escobedo and Christina D. Moon for critical contributions to earlier versions of the manuscript. How and when fungal endophytes can eliminate the plant growth-defence trade-off: mechanistic perspectives. [Extracted from the article]

Tropospheric ozone is among the global change factors that pose a threat to plants and microorganisms. Symbiotic microorganisms can assist plants to cope with stress, but their role in the tolerance of plants to ozone is poorly understood. Here, we subjected endophyte-symbiotic and non-symbiotic plants of Lolium multiflorum , an annual species widely distributed in temperate grasslands, to high and low (i.e., charcoal-filtered air) ozone levels at vegetative and reproductive phases. Exposure to high ozone reduced leaf photochemical efficiency and greenness in both symbiotic and non-symbiotic plants. However, ozone-induced oxidative damage at biochemical level (i.e., lipid peroxidation) was mostly detected in symbiotic plants. Ozone exposure at the vegetative phase did not affect the reproductive investment in seeds, indicating full recovery from stress. Ozone exposure at the reproductive phase reduced biomass and seed production only in symbiotic plants indicating a symbiont-associated cost. At low ozone, endophyte-symbiotic plants showed a steeper slope in the relationship between seed number and seed weight (i.e., a number-weight trade-off) compared to non-symbiotic plants. However, when plants were treated at the reproductive phase, ozone increased the imbalance between seed number and seed weight in both endophyte-symbiotic and non-symbiotic plants. Plants with endophytes at the reproductive stage produced fewer seeds, which were not compensated by increased seed weight. Thus, fungal mycelium growing within ovaries or ozone-induced antioxidant systems may result in costs that finally depress the fitness of plants. Despite ozone pollution could destabilize plant-endophyte mutualisms and render them dysfunctional, other endophyte-mediated benefits (e.g., resistance to herbivory, tolerance to drought) could over-compensate these losses and explain the high incidence of the symbiosis in nature. • Symbiotic and non-symbiotic plants were exposed to low and high ozone (O 3). • Plant fitness was more sensitive to O 3 at reproductive than vegetative stages. • Symbiotic plants exposed to O 3 at flowering displayed reduced investment in reproduction. • O 3 caused a seed number−seed weight trade-off of non-symbiotic plants without compromising fitness. • Low frequency of symbiotic plants may be found in populations under O 3 pollution. [ABSTRACT FROM AUTHOR]