RESUMO
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.
Assuntos
Alcaloides , Endófitos , Epichloe , Festuca , Lolium , Poliaminas , Alcaloides/metabolismo , Alcaloides/análise , Endófitos/química , Endófitos/fisiologia , Epichloe/química , Epichloe/fisiologia , Ergotaminas/metabolismo , Festuca/microbiologia , Festuca/fisiologia , Herbivoria , Compostos Heterocíclicos com 2 Anéis , Alcaloides Indólicos/metabolismo , Lolium/microbiologia , Lolium/fisiologia , Micotoxinas , Defesa das Plantas contra Herbivoria , Poaceae/microbiologia , Poaceae/metabolismo , SimbioseRESUMO
In this work we performed morphological and molecular phylogenetic analyses (based on sequences of calmodulin M [calM], translation-elongation factor 1-α [tefA] and ß-tubulin [tubB] genes) to characterize the diversity of Epichloë endophytes in Bromus setifolius and Phleum alpinum. The phylogenies obtained from the three genes were congruent and allowed differentiation of three lineages of endophytes that also presented morphological differences. One lineage corresponds to the previously described species Epichloë tembladerae, which is present in a wide range of native grasses from Argentina including B. setifolius and P. alpinum. Another genotype isolated only from B. setifolius is a non-hybrid endophyte, a rare condition for the South American Epichloë endophytes. Isolates of this genotype, described herein as a new variety, Epichloë typhina var. aonikenkana, presented waxy colonies at maturity and a low production of conidia. The third lineage, exclusively found in isolates from P. alpinum, is a hybrid between E. typhina and a common ancestor of E. amarillans and E. baconii. Isolates of this lineage produce abundant conidia that are variable in shape and size. Based on its unique phylogenetic position and morphology, we propose the new species, Epichloë cabralii for this lineage. The new combinations Epichloë tembladerae and E. pampeana also are proposed for the previously described Neotyphodium tembladerae and Neotyphodium pampeanum species.
Assuntos
Epichloe/isolamento & purificação , Neotyphodium/isolamento & purificação , Poaceae/microbiologia , Biodiversidade , DNA Fúngico/genética , DNA Espaçador Ribossômico/genética , Epichloe/classificação , Epichloe/genética , Epichloe/crescimento & desenvolvimento , Dados de Sequência Molecular , Neotyphodium/classificação , Neotyphodium/genética , Neotyphodium/crescimento & desenvolvimento , Filogenia , Poaceae/fisiologia , Esporos Fúngicos/classificação , Esporos Fúngicos/genética , Esporos Fúngicos/crescimento & desenvolvimento , Esporos Fúngicos/isolamento & purificação , SimbioseRESUMO
The epichloë endophytes are systemic, constitutive, and often vertically transmitted fungal symbionts of grass species in subfamily Poöideae. Prior studies indicate that several asexual epichloë endophytes (Neotyphodium species) have evolved directly from sexual (Epichloë) species, whereas others evolved by hybridization between two or more endophyte species. In this paper, we investigate the phylogenies of 27 Neotyphodium spp. isolates from 10 native grass species (in 4 tribes) in 22 populations throughout Argentina. Relationships among these fungi and a worldwide collection of epichloë endophytes were estimated by phylogenetic analysis of sequences from variable portions (mainly introns) of genes for beta-tubulin (tub2) and translation elongation factor 1-alpha (tef1). Most of the Argentine endophyte isolates were interspecific hybrids of Epichloë festucae and E. typhina. Only one isolate was a hybrid of a different ancestry, and three isolates were apparently non-hybrid endophytes. These results indicate that interspecific hybridization, which promotes genetic variation, was common during the evolution of the endophytes of Argentine grasses.