Toxin-producing Epichloë bromicola strains symbiotic with the forage grass Elymus dahuricus in China

Abstract

Cool-season grasses (Poaceae subfamily Poöideae) are an important forage component for livestock in western China, and many have seed-transmitted symbionts of the genus Epichloë, fungal endophytes that are broadly distributed geographically and in many tribes of the Poöideae. Epichloë strains can produce any of several classes of alkaloids, of which ergot alkaloids and indole-diterpenes can be toxic to mammalian and invertebrate herbivores, whereas lolines and peramine are more selective against invertebrates. The authors characterized genotypes and alkaloid profiles of Epichloë bromicola isolates symbiotic with Elymus dahuricus, an important forage grass in rangelands of China. The endophyte was seed-transmitted and occasionally produced fruiting bodies (stromata), but its sexual state was not observed on this host. The genome sequence of E. bromicola isolate E7626 from El. dahuricus in Xinjiang Province revealed gene sets for peramine, ergot alkaloids, and indole-diterpenes. In multiplex polymerase chain reaction (PCR) screens of El. dahuricus-endophyte isolates from Beijing and two locations in Shanxi Province, most were also positive for these genes. Ergovaline and other ergot alkaloids, terpendoles and other indole-diterpenes, and peramine were confirmed in El. dahuricus plants with E. bromicola. The presence of ergot alkaloids and indole-diterpenes in this grass is a potential concern for managers of grazing livestock.

Infection Rates and Alkaloid Patterns of Different Grass Species with Systemic Epichloë Endophytes

“…Recently, more emphasis has been placed on evaluating the genetic capability of Epichloë species to produce alkaloids by determining which alkaloid biosynthesis genes are present within the endophyte (9,15,51,52). Understanding which alkaloid biosynthesis genes are present can affirm the alkaloid potential of any given isolate, as much of the alkaloid diversity observed in Epichloë species is due to gene presence/absence polymorphisms that can be easily observed by PCR, providing an effective tool to rapidly evaluate samples from large population sizes (10,12,13,19). Alkaloid chemotypes that do not match the predictions based on PCR have been shown to have altered gene expression (little or no expression) that silences the pathway, or a gene can lack functionality due to the presence of nonsense mutations that would result in a different pathway end product (10,15,19,52,53).…”

“…Peramine synthesis is encoded by a single gene, perA (16), whereas the ergot alkaloids (EAS), indole-diterpenes (IDT), and lolines (LOL) each have multiple genes associated in gene clusters (9,17). Much of the alkaloid diversity present in Epichloë is due to presence or absence of the alkaloid biosynthesis genes, which makes it possible to predict synthesized alkaloids based on detection of genes encoding key pathway steps (10,12,13,18,19).…”

Genetic Diversity of the Symbiotic Fungus Epichloë festucae in Naturally Occurring Host Grass Populations

“…Lolitrem B (LTB), the end product of IDT biosynthesis in E. festucae , was predicted to be produced, if in addition to the genes mentioned above also idtJ produced a PCR band. The prerequisite of the production of terpendole C and lolitrem B was also that the sequence of idtF -gene was functional, without the deletion in the first exon of the gene that causes an inframe stop codon ( Young et al, 2009 ; Shi et al, 2017 ; Yi et al, 2018 ). In addition, presence of idtP gene was checked from our unpublished data in 109 of the F. rubra – E. festucae combinations in the present study.…”

Influence of Epichloë bromicola endophytic fungi on secondary metabolites following alkali tolerance improvement in host, Hordeum bogdanii

“…(2) Polyphenol content: Folin-Ciocalteu method was used to determine the polyphenol content (Shi et al 2018).…”