Separation of four isomers of lysergic acid α-hydroxyethylamide by liquid chromatography and their spectroscopic identification

Ergot Alkaloids Contribute to the Pathogenic Potential of the Fungus Aspergillus leporis

Opportunistically pathogenic fungi have varying potential to cause disease in animals. Factors contributing to their virulence include specialized metabolites, which in some cases evolved in contexts unrelated to pathogenesis. Specialized metabolites that increase fungal virulence in the model insect Galleria mellonella include the ergot alkaloids fumigaclavine C in Aspergillus fumigatus (syn. Neosartorya fumigata) and lysergic acid α-hydroxyethylamide (LAH) in the entomopathogen Metarhizium brunneum. Three species of Aspergillus recently found to accumulate high concentrations of LAH were investigated for their pathogenic potential in G. mellonella. Aspergillus leporis was most virulent, A. hancockii was intermediate, and A. homomorphus had very little pathogenic potential. Aspergillus leporis and A. hancockii emerged from and sporulated on dead insects, thus completing their asexual life cycles. Inoculation by injection resulted in more lethal infections than did topical inoculation, indicating that A. leporis and A. hancockii were preadapted for insect pathogenesis but lacked an effective means to breach the insect's cuticle. All three species accumulated LAH in infected insects, with A. leporis accumulating the most. Concentrations of LAH in A. leporis were similar to those observed in the entomopathogen M. brunneum. LAH was eliminated from A. leporis through a CRISPR/Cas9-based gene knockout, and the resulting strain had reduced virulence to G. mellonella. The data indicate that A. leporis and A. hancockii have considerable pathogenic potential and that LAH increases the virulence of A. leporis. IMPORTANCE Certain environmental fungi infect animals occasionally or conditionally, whereas others do not. Factors that affect the virulence of these opportunistically pathogenic fungi may have originally evolved to fill some other role for the fungus in its primary environmental niche. Among the factors that may improve the virulence of opportunistic fungi are specialized metabolites--chemicals that are not essential for basic life functions but provide producers with an advantage in particular environments or under specific conditions. Ergot alkaloids are a large family of fungal specialized metabolites that contaminate crops in agriculture and serve as the foundations of numerous pharmaceuticals. Our results show that two ergot alkaloid-producing fungi that were not previously known to be opportunistic pathogens can infect a model insect and that, in at least one of the species, an ergot alkaloid increases the virulence of the fungus.

Derivation of the multiply-branched ergot alkaloid pathway of fungi

Ergot alkaloids are a large family of fungal specialized metabolites that are important as toxins in agriculture and as the foundation of powerful pharmaceuticals. Fungi from several lineages and diverse ecological niches produce ergot alkaloids from at least one of several branches of the ergot alkaloid pathway. The biochemical and genetic bases for the different branches have been established and are summarized briefly herein. Several pathway branches overlap among fungal lineages and ecological niches, indicating activities of ergot alkaloids benefit fungi in different environments and conditions. Understanding the functions of the multiple genes in each branch of the pathway allows researchers to parse the abundant genomic sequence data available in public databases in order to assess the ergot alkaloid biosynthesis capacity of previously unexplored fungi. Moreover, the characterization of the genes involved in the various branches provides opportunities and resources for the biotechnological manipulation of ergot alkaloids for experimentation and pharmaceutical development.

Contribution of a novel gene to lysergic acid amide synthesis in Metarhizium brunneum

Objective

The fungus Metarhizium brunneum produces ergot alkaloids of the lysergic acid amide class, most abundantly lysergic acid α-hydroxyethylamide (LAH). Genes for making ergot alkaloids are clustered in the genomes of producers. Gene clusters of LAH-producing fungi contain an α/β hydrolase fold protein-encoding gene named easP whose presence correlates with LAH production but whose contribution to LAH synthesis in unknown. We tested whether EasP contributes to LAH accumulation through gene knockout studies.

Results

We knocked out easP in M. brunneum via a CRISPR/Cas9-based approach, and accumulation of LAH was reduced to less than half the amount observed in the wild type. Because LAH accumulation was reduced and not eliminated, we identified and mutated the only close homolog of easP in the M. brunneum genome, a gene we named estA. An easP/estA double mutant did not differ from the easP mutant in lysergic acid amide accumulation, indicating estA had no role in the pathway. We conclude EasP contributes to LAH accumulation but is not absolutely required. Either a gene encoding redundant function and lacking sequence identity with easP resides outside the ergot alkaloid synthesis gene cluster, or EasP plays an accessory role in the synthesis of LAH.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13104-022-06068-2.

Diversification of ergot alkaloids and heritable fungal symbionts in morning glories

Heritable microorganisms play critical roles in life cycles of many macro-organisms but their prevalence and functional roles are unknown for most plants. Bioactive ergot alkaloids produced by heritable Periglandula fungi occur in some morning glories (Convolvulaceae), similar to ergot alkaloids in grasses infected with related fungi. Ergot alkaloids have been of longstanding interest given their toxic effects, psychoactive properties, and medical applications. Here we show that ergot alkaloids are concentrated in four morning glory clades exhibiting differences in alkaloid profiles and are more prevalent in species with larger seeds than those with smaller seeds. Further, we found a phylogenetically-independent, positive correlation between seed mass and alkaloid concentrations in symbiotic species. Our findings suggest that heritable symbiosis has diversified among particular clades by vertical transmission through seeds combined with host speciation, and that ergot alkaloids are particularly beneficial to species with larger seeds. Our results are consistent with the defensive symbiosis hypothesis where bioactive ergot alkaloids from Periglandula symbionts protect seeds and seedlings from natural enemies, and provide a framework for exploring microbial chemistry in other plant-microbe interactions.

Independent Evolution of a Lysergic Acid Amide in Aspergillus Species

Ergot alkaloids derived from lysergic acid have impacted humanity as contaminants of crops and as the bases of pharmaceuticals prescribed to treat dementia, migraines, and other disorders. Several plant-associated fungi in the Clavicipitaceae produce lysergic acid derivatives, but many of these fungi are difficult to culture and manipulate. Some Aspergillus species, which may be more ideal experimental and industrial organisms, contain an alternate branch of the ergot alkaloid pathway, but none were known to produce lysergic acid derivatives. We mined the genomes of Aspergillus species for ergot alkaloid synthesis (eas) gene clusters and discovered that three species, A. leporis, A. homomorphus, and A. hancockii, had eas clusters indicative of the capacity to produce a lysergic acid amide. In culture, A. leporis, A. homomorphus, and A. hancockii produced lysergic acid amides, predominantly lysergic acid α-hydroxyethylamide (LAH). Aspergillus leporis and A. homomorphus produced high concentrations of LAH and secreted most of their ergot alkaloid yield into the culture medium. Phylogenetic analyses indicated that genes encoding enzymes leading to the synthesis of lysergic acid were orthologous to those of the lysergic acid amide-producing Clavicipitaceae; however, genes to incorporate lysergic acid into an amide derivative evolved from different ancestral genes in the Aspergillus species. Our data demonstrate that fungi outside the Clavicipitaceae produce lysergic acid amides and indicate that the capacity to produce lysergic acid evolved once, but the ability to insert it into LAH evolved independently in Aspergillus species and the Clavicipitaceae. The LAH-producing Aspergillus species may be useful for the study and production of these pharmaceutically important compounds. IMPORTANCE Lysergic acid derivatives are specialized metabolites with historical, agricultural, and medical significance and were known heretofore only from fungi in one family, the Clavicipitaceae. Our data show that several Aspergillus species, representing a different family of fungi, also produce lysergic acid derivatives and that the ability to put lysergic acid into its amide forms evolved independently in the two lineages of fungi. From microbiological and pharmaceutical perspectives, the Aspergillus species may represent better experimental and industrial organisms than the currently employed lysergic acid producers of the plant-associated Clavicipitaceae. The observation that both lineages independently evolved the derivative lysergic acid α-hydroxyethylamide (LAH), among many possible lysergic acid amides, suggests selection for this metabolite.

A Baeyer-Villiger Monooxygenase Gene Involved in the Synthesis of Lysergic Acid Amides Affects the Interaction of the Fungus Metarhizium brunneum with Insects

Several fungi, including the plant root symbiont and insect pathogen Metarhizium brunneum, produce lysergic acid amides via a branch of the ergot alkaloid pathway. Lysergic acid amides include important pharmaceuticals and pharmaceutical lead compounds and have potential ecological significance, making knowledge of their biosynthesis relevant. Many steps in the biosynthesis of lysergic acid amides have been determined, but terminal steps in the synthesis of lysergic acid α-hydroxyethylamide (LAH)-by far the most abundant lysergic acid amide in M. brunneum-are unknown. Ergot alkaloid synthesis (eas) genes are clustered in the genomes of fungi that produce these compounds, and the eas clusters of LAH producers contain two uncharacterized genes (easO and easP) not found in fungi that do not produce LAH. Knockout of easO via a CRISPR-Cas9 approach eliminated LAH and resulted in accumulation of the alternate lysergic acid amides lysergyl-alanine and ergonovine. Despite the elimination of LAH, the total concentration of lysergic acid derivatives was not affected significantly by the mutation. Complementation with a wild-type allele of easO restored the ability to synthesize LAH. Substrate feeding studies indicated that neither lysergyl-alanine nor ergonovine were substrates for the product of easO (EasO). EasO had structural similarity to Baeyer-Villiger monooxygenases (BVMOs), and labeling studies with deuterated alanine supported a role for a BVMO in LAH biosynthesis. The easO knockout had reduced virulence to larvae of the insect Galleria mellonella, indicating that LAH contributes to virulence of M. brunneum on insects and that LAH has biological activities different from ergonovine and lysergyl-alanine. IMPORTANCE Fungi in the genus Metarhizium are important plant root symbionts and insect pathogens. They are formulated commercially to protect plants from insect pests. Several Metarhizium species, including M. brunneum, were recently shown to produce ergot alkaloids, a class of specialized metabolites studied extensively in other fungi because of their importance in agriculture and medicine. A biological role for ergot alkaloids in Metarhizium species had not been demonstrated previously. Moreover, the types of ergot alkaloids produced by Metarhizium species are lysergic acid amides, which have served directly or indirectly as important pharmaceutical compounds. The terminal steps in the synthesis of the most abundant lysergic acid amide in Metarhizium species and several other fungi (LAH) have not been determined. The results of this study demonstrate the role of a previously unstudied gene in LAH synthesis and indicate that LAH contributes to virulence of M. brunneum on insects.

Genetic Reprogramming of the Ergot Alkaloid Pathway of Metarhizium brunneum

Ergot alkaloids are important specialized fungal metabolites that are used to make potent pharmaceuticals for neurological diseases and disorders. Lysergic acid (LA) and dihydrolysergic acid (DHLA) are desirable lead compounds for pharmaceutical semisynthesis but are typically transient intermediates in the ergot alkaloid and dihydroergot alkaloid pathways. Previous work with Neosartorya fumigata demonstrated strategies to produce these compounds as pathway end products, but their percent yield (percentage of molecules in product state as opposed to precursor state) was low. Moreover, ergot alkaloids in N. fumigata are typically retained in the fungus as opposed to being secreted. We used clustered regularly interspaced short palindromic repeat (CRISPR)-CRISPR-associated protein 9 (Cas9) and heterologous expression approaches to engineer these compounds in Metarhizium brunneum, representing an alternate expression host from a different lineage of fungi. The relative percent yields of LA (86.9%) and DHLA (72.8%) were much higher than those calculated here for previously engineered strains of N. fumigata (2.6% and 2.0%, respectively). Secretion of these alkaloids also was measured, with averages of 98.4% of LA and 87.5% of DHLA being secreted into the growth medium; both values were significantly higher than those measured for the N. fumigata derivatives (both of which were less than 5.6% secreted). We used a similar approach to engineer a novel dihydroergot alkaloid in M. brunneum and, through high-performance liquid chromatography-mass spectrometry (LC-MS) analyses, provisionally identified it as the dihydrogenated form of lysergic acid α-hydroxyethylamide (dihydro-LAH). The engineering of these strains provides a strategy for producing novel and pharmaceutically important chemicals in a fungus more suitable for their production.IMPORTANCE Ergot alkaloids derived from LA or DHLA are the bases for numerous pharmaceuticals with applications in the treatment of dementia, migraines, hyperprolactinemia, and other conditions. However, extraction of ergot alkaloids from natural sources is inefficient, and their chemical synthesis is expensive. The ability to control and redirect ergot alkaloid synthesis in fungi may allow more efficient production of these important chemicals and facilitate research on novel derivatives. Our results show that Metarhizium brunneum can be engineered to efficiently produce and secrete LA and DHLA and, also, to produce a novel derivative of DHLA not previously found in nature. The engineering of dihydroergot alkaloids, including a novel species, is important because very few natural sources of these compounds are known. Our approach establishes a platform with which to use M. brunneum to study the production of other ergot alkaloids, specifically those classified as lysergic acid amides and dihydroergot alkaloids.

Several Metarhizium Species Produce Ergot Alkaloids in a Condition-Specific Manner

Genomic sequence data indicate that certain fungi in the genus Metarhizium have the capacity to produce lysergic acid-derived ergot alkaloids, but accumulation of ergot alkaloids in these fungi has not been demonstrated previously. We assayed several Metarhizium species grown under different conditions for accumulation of ergot alkaloids. Isolates of M. brunneum and M. anisopliae accumulated the lysergic acid amides lysergic acid α-hydroxyethyl amide, ergine, and ergonovine on sucrose-yeast extract agar but not on two other tested media. Isolates of six other Metarhizium species did not accumulate ergot alkaloids on sucrose-yeast extract agar. Conidia of M. brunneum lacked detectable ergot alkaloids, and mycelia of this fungus secreted over 80% of their ergot alkaloid yield into the culture medium. Isolates of M. brunneum, M. flavoviride, M. robertsii, M. acridum, and M. anisopliae produced high concentrations of ergot alkaloids in infected larvae of the model insect Galleria mellonella, but larvae infected with M. pingshaense, M. album, M. majus, and M. guizhouense lacked detectable ergot alkaloids. Alkaloid concentrations were significantly higher when insects were alive (as opposed to killed by freezing or gas) at the time of inoculation with M. brunneum Roots of corn and beans were inoculated with M. brunneum or M. flavoviride and global metabolomic analyses indicated that the inoculated roots were colonized, though no ergot alkaloids were detected. The data demonstrate that several Metarhizium species produce ergot alkaloids of the lysergic acid amide class and that production of ergot alkaloids is tightly regulated and associated with insect colonization.IMPORTANCE Our discovery of ergot alkaloids in fungi of the genus Metarhizium has agricultural and pharmaceutical implications. Ergot alkaloids produced by other fungi in the family Clavicipitaceae accumulate in forage grasses or grain crops; in this context they are considered toxins, though their presence also may deter or kill insect pests. Our data report ergot alkaloids in Metarhizium species and indicate a close association of ergot alkaloid accumulation with insect colonization. The lack of accumulation of alkaloids in spores of the fungi and in plants colonized by the fungi affirms the safety of using Metarhizium species as biocontrol agents. Ergot alkaloids produced by other fungi have been exploited to produce powerful pharmaceuticals. The class of ergot alkaloids discovered in Metarhizium species (lysergic acid amides) and their secretion into the growth medium make Metarhizium species a potential platform for future studies on ergot alkaloid synthesis and modification.

Ergot Alkaloids of the Family Clavicipitaceae

Ergot alkaloids are highly diverse in structure, exhibit diverse effects on animals, and are produced by diverse fungi in the phylum Ascomycota, including pathogens and mutualistic symbionts of plants. These mycotoxins are best known from the fungal family Clavicipitaceae and are named for the ergot fungi that, through millennia, have contaminated grains and caused mass poisonings, with effects ranging from dry gangrene to convulsions and death. However, they are also useful sources of pharmaceuticals for a variety of medical purposes. More than a half-century of research has brought us extensive knowledge of ergot-alkaloid biosynthetic pathways from common early steps to several taxon-specific branches. Furthermore, a recent flurry of genome sequencing has revealed the genomic processes underlying ergot-alkaloid diversification. In this review, we discuss the evolution of ergot-alkaloid biosynthesis genes and gene clusters, including roles of gene recruitment, duplication and neofunctionalization, as well as gene loss, in diversifying structures of clavines, lysergic acid amides, and complex ergopeptines. Also reviewed are prospects for manipulating ergot-alkaloid profiles to enhance suitability of endophytes for forage grasses.

Genetics, genomics and evolution of ergot alkaloid diversity

The ergot alkaloid biosynthesis system has become an excellent model to study evolutionary diversification of specialized (secondary) metabolites. This is a very diverse class of alkaloids with various neurotropic activities, produced by fungi in several orders of the phylum Ascomycota, including plant pathogens and protective plant symbionts in the family Clavicipitaceae. Results of comparative genomics and phylogenomic analyses reveal multiple examples of three evolutionary processes that have generated ergot-alkaloid diversity: gene gains, gene losses, and gene sequence changes that have led to altered substrates or product specificities of the enzymes that they encode (neofunctionalization). The chromosome ends appear to be particularly effective engines for gene gains, losses and rearrangements, but not necessarily for neofunctionalization. Changes in gene expression could lead to accumulation of various pathway intermediates and affect levels of different ergot alkaloids. Genetic alterations associated with interspecific hybrids of Epichloë species suggest that such variation is also selectively favored. The huge structural diversity of ergot alkaloids probably represents adaptations to a wide variety of ecological situations by affecting the biological spectra and mechanisms of defense against herbivores, as evidenced by the diverse pharmacological effects of ergot alkaloids used in medicine.

Diversification of ergot alkaloids in natural and modified fungi

Several fungi in two different families--the Clavicipitaceae and the Trichocomaceae--produce different profiles of ergot alkaloids, many of which are important in agriculture and medicine. All ergot alkaloid producers share early steps before their pathways diverge to produce different end products. EasA, an oxidoreductase of the old yellow enzyme class, has alternate activities in different fungi resulting in branching of the pathway. Enzymes beyond the branch point differ among lineages. In the Clavicipitaceae, diversity is generated by the presence or absence and activities of lysergyl peptide synthetases, which interact to make lysergic acid amides and ergopeptines. The range of ergopeptines in a fungus may be controlled by the presence of multiple peptide synthetases as well as by the specificity of individual peptide synthetase domains. In the Trichocomaceae, diversity is generated by the presence or absence of the prenyl transferase encoded by easL (also called fgaPT1). Moreover, relaxed specificity of EasL appears to contribute to ergot alkaloid diversification. The profile of ergot alkaloids observed within a fungus also is affected by a delayed flux of intermediates through the pathway, which results in an accumulation of intermediates or early pathway byproducts to concentrations comparable to that of the pathway end product.

Ergot alkaloids--sources, structures and analytical methods

Natural sources, i.e. fungal strains and species producing ergot alkaloids (EA), are surveyed together with the chemical structures of EA and a list of new natural EA discovered in the last three decades. Other topics include new efficient chromatographic methods (HPLC) for the separation and isolation of new natural EA and also immunological methods of EA detection.

The use of the PREP system for handling of body fluids

The Du Pont PREP automated sample processor is a centrifugally based, microprocessor controlled instrument that was designed for extraction of samples from biological fluids. Extraction takes place in cartridges containing either organic resins or bonded silica packings as extraction sorbants. This paper will discuss the application of several lipophilic and ion exchange sorbants to the extraction of biological samples from body fluids. The advantages of these different types of sorbants will be compared and their performance with automated sample preparation will be shown. A variety of applications including the extraction of benzodiazepine, barbiturate, aminoglycoside and anticonvulsant drugs and their metabolites from serum, urine, and tissue homogenates will be discussed.