page_title: Loline alkaloid
section_title: Production and distribution in the grass plant
hierarchical_section_title: Loline alkaloid / Production and distribution in the grass plant
caption_attribution_description: English: Blue-stained serpentine Neotyphodium coenophialum mycelia inhabiting the intercellular spaces of tall fescue leaf sheath tissue. Magnified 400x. Français&#160;: Filament mycélien (coloré en bleu) de Neotyphodium coenophialum dans l'espace intercellulaire d'un tissu de gaine foliaire de Festuca arundinacea (grossi 400 fois).
context_page_description: A loline alkaloid is a member of the 1-aminopyrrolizidines, which are bioactive natural products with several distinct biological and chemical features. The lolines are insecticidal and insect-deterrent compounds that are produced in grasses infected by endophytic fungal symbionts of the genus Epichloë. Lolines increase resistance of endophyte-infected grasses to insect herbivores, and may also protect the infected plants from environmental stresses such as drought and spatial competition. They are alkaloids, organic compounds containing basic nitrogen atoms. The basic chemical structure of the lolines comprises a saturated pyrrolizidine ring, a primary amine at the C-1 carbon, and an internal ether bridge—a hallmark feature of the lolines, which is uncommon in organic compounds—joining two distant ring carbons. Different substituents at the C-1 amine, such as methyl, formyl, and acetyl groups, yield loline species that have variable bioactivity against insects. Besides endophyte–grass symbiota, loline alkaloids have also been identified in some other plant species; namely, Adenocarpus species and Argyreia mollis.
context_section_description: Lolines are produced by several grass–endophyte symbioses involving epichloae species, often along with other bioactive metabolites including ergot alkaloids and indole diterpenoids, and the unusual pyrrolopyrazine alkaloid, peramine, which is not found in other biological communities or organisms. The lolines are produced at levels, however, that can exceed 10 mg/g grass tissue (ranging from 2–20,000 μg/g), exceeding the concentrations of the other endophyte alkaloids by >1000-fold. Lolines produced in the grasses Lolium pratense (syn. Festuca pratensis, meadow fescue) and tall fescue infected by  N. uncinatum and N. coenophialum (see Fig. 3), respectively, exhibit variable concentrations in grass tissues. Higher loline concentrations (100–1000 μg/g) are present in the seeds and in younger leaf tissues, and the lolines display seasonal changes in concentration levels throughout the plant. The periodical appearance of tissues with high loline concentrations, such as flowering stems and seeds, contributes to this seasonal variation. Loline concentrations often increase in grass tissues regrown after defoliation and clipping of plants, suggesting an inducible defense response mechanism, involving both symbiotic partners. However, this increase appears to be due to higher loline levels in younger leaves compared to older leaves, but loline increases resembling inducible plant defenses have also been reported. Variation of loline concentration with the developmental stage of specific grass tissues suggests regulation of in planta loline distributions, providing greater protection of newly grown or embryonic tissues against attacks by insects. Surprisingly, exogenous application of the plant signaling compound, methyl jasmonate—which commonly signals predation by insects—decreases expression of the genes for the lolines. The factors that control loline production vary also among endophyte-infected grass tissues: whereas plant-supplied amino acids that are loline precursors limit accumulation of lolines in many grass tissues, their production in tissues that bear external mycelial growth for fungal reproduction (stromata) is regulated by the expression of loline genes.
caption: Figure 3. Neotyphodium coenophialum hyphae in tall fescue leaf tissue. Lolines commonly accumulate in the N. coenophialum–tall fescue symbiosis, providing protection from insects and other environmental stresses.[1]
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