Inactivation of the indole-diterpene biosynthetic gene cluster of Claviceps paspali by Agrobacterium-mediated gene replacement

An Update in Claviceps paspali Disease: A Comprehensive Analysis on Field and Greenhouse Paspalum spp. Infection

Paspalum L. is a genus of the Poaceae family, with many species serving as well-adapted forage plants in subtropical climates and continuous grazing systems. However, Claviceps paspali, an ascomycete of the order Hypocreales, represents a major threat to the Paspalum species. This fungus induces ergot disease, characterized by the replacement of infected flower seeds with sclerotia, which adversely affects seed production and animal health through mycotoxin production. Although ergot disease is reported in many countries, no totally resistant Paspalum cultivars have been reported for commercial use. This study comparatively evaluated disease development in six Paspalum species under greenhouse conditions with three specific isolates of C. paspali, along with field trials. In addition, field isolates of C. paspali were analyzed for phenotypic characteristics and phylogenetic relationships. Greenhouse evaluation revealed variable susceptibility among Paspalum species, with P. malacophyllum, P. notatum, and P. umbrosum being the most resistant. In field trials P. dilatatum showed the highest severity index, and P. umbrosum and P. malacophyllum were less affected. The phenotypic characterization of 22 C. paspali isolates showed variability in pigmentation and growth rates, with potato dextrose agar being the culture medium in which the highest growth rate was observed. Phylogenetic analysis of the isolates identified two well-supported lineages between C. paspali species. This research reports an ergot resistance gradient among Paspalum species, identifying genuine sources of resistance. In addition, virulent isolates of C. paspali potentially useful for rapid screening of accessions or crosses in Paspalum breeding programs were identified.[Formula: see text] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Ergot alkaloid control in biotechnological processes and pharmaceuticals (a mini review)

The control of ergot alkaloids in biotechnological processes is important in the context of obtaining new strain producers and studying the mechanisms of the biosynthesis, accumulation and secretion of alkaloids and the manufacturing of alkaloids. In pharmaceuticals, it is important to analyze the purity of raw materials, especially those capable of racemization, quality control of dosage forms and bulk drugs, stability during storage, etc. This review describes the methods used for qualitative and quantitative chemical analysis of ergot alkaloids in tablets and pharmaceutic forms, liquid cultural media and mycelia from submerged cultures of ergot and other organisms producing ergoalkaloid, sclerotias of industrial Claviceps spp. parasitic strains. We reviewed analytical approaches for the determination of ergopeptines (including their dihydro- and bromine derivatives) and semisynthetic ergot-derived medicines such as cabergoline, necergoline and pergolide, including precursors for their synthesis. Over the last few decades, strategies and approaches for the analysis of ergoalkaloids for medical use have changed, but the general principles and objectives have remained the same as before. These changes are related to the development of new genetically improved strains producing ergoalkaloids and the development of technologies for the online control of biotechnological processes and pharmaceutical manufacturing ("process analytical technologies," PAT). Overall, the industry is moving toward "smart manufacturing." The development of approaches to production cost estimation and product quality management, manufacturing management, increasing profitability and reducing the negative impact on personnel and the environment are integral components of sustainable development. Analytical approaches for the analysis of ergot alkaloids in pharmaceutical raw materials should have high enough specificity for the separation of dihydro derivatives, enantiomers and R-S epimers of alkaloids, but low values of the quantitative detection limit are less frequently needed. In terms of methodology, detection methods based on mass spectrometry have become more developed and widespread, but NMR analysis remains in demand because of its high accuracy and specificity. Both rapid methods and liquid chromatography remain in demand in routine practice, with rapid analysis evolving toward higher accuracy owing to improved analytical performance and new equipment. New composite electrochemical sensors (including disposable sensors) have demonstrated potential for real-time process control.

Construction of an efficient Claviceps paspali cell factory for lysergic acid production

Lysergic acid (LA) is the key precursor of ergot alkaloids, and its derivatives have been used extensively for the treatment of neurological disorders. However, the poor fermentation efficiency limited its industrial application. At the same time, the hardship of genetic manipulation has hindered the metabolic engineering of Claviceps strains to improve the LA titer further. In this study, an efficient genetic manipulation system based on the protoplast-mediated transformation was established in the industrial strain Claviceps paspali. On this basis, the gene lpsB located in the ergot alkaloids biosynthetic gene cluster was deleted to construct the LA-producing cell factory. Plackett-Burman and Box-Behnken designs were used in shaking flasks, achieving an optimal fermentation medium composition. The final titer of LA and iso-lysergic acid (ILA) reached 3.7 g·L^-1, which was 4.6 times higher than that in the initial medium. Our work provides an efficient strategy for the biosynthesis of LA and ILA and lays the groundwork for its industrial production.

The Biosynthesis Related Enzyme, Structure Diversity and Bioactivity Abundance of Indole-Diterpenes: A Review

Indole diterpenes are a large class of secondary metabolites produced by fungi, possessing a cyclic diterpenoid backbone and an indole moiety. Novel structures and important biological activity have made indole diterpenes one of the focuses of synthetic chemists. Although the discovery, identification, structural diversity, biological activity and especially structure-activity relationship of indole diterpenes have been reported in some papers in recent years, they are absent of a systematic and comprehensive analysis, and there is no elucidation of enzymes related to this kind of natural product. Therefore, it is necessary to summarize the relevant reports to provide new perspectives for the following research. In this review, for the first time, the function of related synthases and the structure-activity relationship of indole diterpenes are expounded, and the recent research advances of them are emphasized.

Improving Ergometrine Production by easO and easP Knockout in Claviceps paspali

Ergometrine is widely used for the treatment of excessive postpartum uterine bleeding. Claviceps paspali is a common species for industrial production of ergometrine, which is often accompanied by lysergic acid α-hydroxyethylamide (LAH) and lysergic acid amide (LAA). Currently, direct evidence on the biosynthetic mechanism of LAH and LAA from lysergic acid in C. paspali is absent, except that LAH and LAA share the common precursor with ergometrine and LAA is spontaneously transformed from LAH. A comparison of the gene clusters between C. purpurea and C. paspali showed that the latter harbored the additional easO and easP genes. Thus, the knockout of easO and easP in the species should not only improve the ergometrine production but also elucidate the function. In this study, gene knockout of C. paspali by homologous recombination yielded two mutants ∆easOhetero-1 and ∆easPhetero-34 with ergometrine titers of 1559.36 mg∙L−1 and 837.57 mg∙L−1, which were four and two times higher than that of the wild-type control, respectively. While the total titer of LAH and LAA of ∆easOhetero-1 was lower than that of the wild-type control. The Aspergillus nidulans expression system was adopted to verify the function of easO and easP. Heterologous expression in A. nidulans further demonstrated that easO, but not easP, determines the formation of LAA.

Synthesis of rearranged indole diterpenes of the paxilline type

Covering: up to 2021Rearranged indole diterpenes of the paxilline type comprise a large group of fungal metabolites that possess diverse structural features and potentially useful biological effects. The unique indoloterpenoid motif, which is common to all congeners, was first confirmed by crystallographic studies of paxilline. This family of natural products has fascinated organic chemists for the past four decades and has inspired numerous syntheses and synthetic approaches. The present review highlights efforts that have laid the foundation and introduced new directions to this field of natural product synthesis. The introduction includes a summary of biosynthetic considerations and biological activities, the main body of the manuscript provides a detailed discussion of selected syntheses, and the review concludes with a brief outlook on the future of the field.

Genome-wide analysis of Claviceps paspali: insights into the secretome of the main species causing ergot disease in Paspalum spp

BACKGROUND

The phytopatogen Claviceps paspali is the causal agent of Ergot disease in Paspalum spp., which includes highly productive forage grasses such as P. dilatatum. This disease impacts dairy and beef production by affecting seed quality and producing mycotoxins that can affect performance in feeding animals. The molecular basis of pathogenicity of C. paspali remains unknown, which makes it more difficult to find solutions for this problem. Secreted proteins are related to fungi virulence and can manipulate plant immunity acting on different subcellular localizations. Therefore, identifying and characterizing secreted proteins in phytopathogenic fungi will provide a better understanding of how they overcome host defense and cause disease. The aim of this work is to analyze the whole genome sequences of three C. paspali isolates to obtain a comparative genome characterization based on possible secreted proteins and pathogenicity factors present in their genome. In planta RNA-seq analysis at an early stage of the interaction of C. paspali with P. dilatatum stigmas was also conducted in order to determine possible secreted proteins expressed in the infection process.

RESULTS

C. paspali isolates had compact genomes and secretome which accounted for 4.6-4.9% of the predicted proteomes. More than 50% of the predicted secretome had no homology to known proteins. RNA-Seq revealed that three protein-coding genes predicted as secreted have mayor expression changes during 1 dpi vs 4 dpi. Also, three of the first 10 highly expressed genes in both time points were predicted as effector-like. CAZyme-like proteins were found in the predicted secretome and the most abundant family could be associated to pectine degradation. Based on this, pectine could be a main component affected by the cell wall degrading enzymes of C. paspali.

CONCLUSIONS

Based on predictions from DNA sequence and RNA-seq, unique probable secreted proteins and probable pathogenicity factors were identified in C. paspali isolates. This information opens new avenues in the study of the biology of this fungus and how it modulates the interaction with its host. Knowledge of the diversity of the secretome and putative pathogenicity genes should facilitate future research in disease management of Claviceps spp.

An efficient genetic transformation system for Chinese medicine fungus Tolypocladium ophioglossoides

Tolypocladium ophioglossoides is a rare and valuable fungus extensively used in Chinese medicine for relieving postmenopausal syndrome in women yet its bioactive molecules are unknown. To explore its molecular mechanisms, we have developed a reliable Agrobacterium-mediated transformation system using the selective marker: the chlorimuron ethyl-resistance gene sur. For this purpose, we firstly constructed a T-DNA binary vector system and then improved the transformation efficiency by optimizing conditional parameters including the Agrobacterium tumefaciens concentration, the conidia number of T. ophioglossoides, the co-culture time and the concentration of acetosyringone. Furthermore, we have knocked-out the ku70 gene，which is a key gene in non-homologous end joining (NHEJ) DNA repair pathway，and the effect of the length of the homologous arms (HA) on the genetic transformation efficacy was also examined, which increased by 60% when HA was about 3 kb in length. Our results suggest that the genetic transformation system is efficient and feasible for the truffle-parasite fungus T. ophioglossoides, which can further be used in large-scale experiments for characterization of genes of interest in future work.

Supplementation of Aspergillus glaucus with gfdB gene encoding a glycerol 3-phosphate dehydrogenase in Aspergillus nidulans

In Aspergillus nidulans, there are two putative glycerol 3-phosphate dehydrogenases encoded by the genes gfdA and gfdB, while the genome of the osmophilic Aspergillus glaucus harbors only the ortholog of the A. nidulans gfdA gene. Our aim was to insert the gfdB gene into the genome of A. glaucus, and we reached this goal with the adaptation of the Agrobacterium tumefaciens-mediated transformation method. We tested the growth of the gfdB-complemented A. glaucus strains on a medium containing 2 mol l^-1 sorbitol in the presence of oxidative stress generating agents such as tert-butyl hydroperoxide, H₂ O₂ , menadione sodium bisulfite, as well as the cell wall integrity stress-inducing agent Congo Red and the heavy metal stress eliciting CdCl₂ . The growth of the complemented strains was significantly higher than that of the wild-type strain on media supplemented with these stress generating agents. The A. nidulans ΔgfdB mutant was also examined under the same conditions and resulted in a considerably lower growth than that of the control strain in all stress exposure experiments. Our results shed light on the fact that the gfdB gene from A. nidulans was also involved in the stress responses of the complemented A. glaucus strains supporting our hypothesis on the antioxidant function of GfdB in the Aspergilli. Nevertheless, the osmotolerant nature of A. glaucus could not be explained by the lack of the gfdB gene in A. glaucus, as we hypothesized earlier.

Plants make galls to accommodate foreigners: some are friends, most are foes

At the colonization site of a foreign entity, plant cells alter their trajectory of growth and development. The resulting structure - a plant gall - accommodates various needs of the foreigner, which are phylogenetically diverse: viruses, bacteria, protozoa, oomycetes, true fungi, parasitic plants, and many types of animals, including rotifers, nematodes, insects, and mites. The plant species that make galls also are diverse. We assume gall production costs the plant. All is well if the foreigner provides a gift that makes up for the cost. Nitrogen-fixing nodule-inducing bacteria provide nutritional services. Gall wasps pollinate fig trees. Unfortunately for plants, most galls are made for foes, some of which are deeply studied pathogens and pests: Agrobacterium tumefaciens, Rhodococcus fascians, Xanthomonas citri, Pseudomonas savastanoi, Pantoea agglomerans, 'Candidatus' phytoplasma, rust fungi, Ustilago smuts, root knot and cyst nematodes, and gall midges. Galls are an understudied phenomenon in plant developmental biology. We propose gall inception for discovering unifying features of the galls that plants make for friends and foes, talk about molecules that plants and gall-inducers use to get what they want from each other, raise the question of whether plants colonized by arbuscular mycorrhizal fungi respond in a gall-like manner, and present a research agenda.

Functional characterization of the idtF and idtP genes in the Claviceps paspali indole diterpene biosynthetic gene cluster

Claviceps paspali is used in the pharmaceutical industry for the production of ergot alkaloids. This fungus also biosynthesizes paspalitrems, indole diterpene (IDT) mycotoxins that cause significant economic losses in agriculture and represent safety concerns for ergot alkaloid manufacture. Here, we use Agrobacterium-mediated transformation to replace the idtP and the idtF genes in the IDT biosynthetic gene cluster of C. paspali with a selectable marker gene. We show that the ΔidtP knockout mutant produces paspaline, the first IDT intermediate of the pathway. The ΔidtF strain produces unprenylated IDTs such as paspalinine and paspaline. These experiments validate the function of idtP as the gene encoding the cytochrome P450 monooxygenase that oxidizes and demethylates paspaline to produce 13-desoxypaxilline, and that of idtF as the gene that encodes the α-prenyltransferase that prenylates paspalinine at the C20 or the C21 positions to yield paspalitrems A and C, respectively. In addition, we also show that axenic cultures of the wild type, the ΔidtP and the ΔidtF mutant C. paspali strains fail to produce an assembly of IDTs that are present in C. paspali–Paspalum spp. associations.

Diversity of Claviceps paspali reveals unknown lineages and unique alkaloid genotypes

Claviceps species affecting Paspalum spp. are a serious problem, as they infect forage grasses such as Paspalum dilatatum and P. plicatulum, producing the ergot disease. The ascomycete C. paspali is known to be the pathogen responsible for this disease in both grasses. This fungus produces alkaloids, including ergot alkaloids and indole-diterpenes, that have potent neurotropic activities in mammals. A total of 32 isolates from Uruguay were obtained from infected P. dilatatum and P. plicatulum. Isolates were phylogenetically identified using partial sequences of the genes coding for the second largest subunit of RNA polymerase subunit II (RPB2), translation elongation factor 1-α (TEF1), β-tubulin (TUB2), and the nuc rDNA 28S subunit (28S). Isolates were also genotyped by randomly amplified polymorphic DNA (RAPD) and presence of genes within the ergot alkaloid (EAS) and indole-diterpene (IDT) biosynthetic gene clusters. This study represents the first genetic characterization of several isolates of C. paspali. The results from this study provide insight into the genetic and genotypic diversity of Claviceps paspali present in P. dilatatum and suggest that isolates from P. plicatulum could be considered an ecological subspecies or specialized variant of C. paspali. Some of these isolates show hypothetical alkaloid genotypes never reported before.

Advances in targeting and heterologous expression of genes involved in the synthesis of fungal secondary metabolites

The revolutionary discovery of penicillin only marks the start of our exploration for valuable fungal natural products. Advanced genome sequencing technologies have translated the fungal genome into a huge reservoir of "recipes" - biosynthetic gene clusters (BGCs) - for biosynthesis. Studying complex fungal genetics demands specific gene manipulation strategies. This review summarizes the current progress in efficient gene targeting in fungal cells and heterologous expression systems for expressing fungal BGCs of fungal secondary metabolites.

Identification and expression profiling analysis of NBS-LRR genes involved in Fusarium oxysporum f.sp. conglutinans resistance in cabbage

As one of the most important resistance (R) gene families in plants, the NBS-LRR genes, encoding proteins with nucleotide-binding site (NBS) and leucine-rich repeat (LRR) domains, play significant roles in resisting pathogens. The published genomic data for cabbage (Brassica oleracea L.) provide valuable data to identify and characterize the genomic organization of cabbage NBS-LRR genes. Ultimately, we identified 105 TIR (N-terminal Toll/interleukin-1 receptor)-NBS-LRR (TNL) genes and 33 CC (coiled-coil)-NBS-LRR (CNL) genes. Further research indicated that 50.7% of the 138 NBS-LRR genes exist in 27 clusters and there are large differences among the gene structures and protein characteristics. Conserved motif and phylogenetic analysis showed that the structures of TNLs and CNLs were similar, with some differences. These NBS-LRRs are evolved under negative selection and mostly arose from whole-genome duplication events during evolution. Tissue-expression profiling of NBS-LRR genes revealed that 37.1% of the TNL genes are highly or specifically expressed in roots, especially the genes on chromosome 7 (76.5%). Digital gene expression and reverse transcription PCR analyses revealed the expression patterns of the NBS-LRR genes upon challenge by Fusarium oxysporum f.sp. conglutinans: nine genes were upregulated, and five were downregulated. The major resistance gene Foc1 probably works together with the other four genes in the same cluster to resist F. oxysporum infection.

Tremorgenic and neurotoxic paspaline-derived indole-diterpenes: biosynthetic diversity, threats and applications

Indole-diterpenes (IDTs) such as the aflatrems, janthitrems, lolitrems, paspalitrems, penitrems, shearinines, sulpinines, and terpendoles are biogenetically related but structurally varied tremorgenic and neurotoxic mycotoxins produced by fungi. All these metabolites derive from the biosynthetic intermediate paspaline, a frequently occurring IDT on its own right. In this comprehensive review, we highlight the similarities and differences of the IDT biosynthetic pathways that lead to the generation of the main paspaline-derived IDT subgroups. We survey the taxonomic distribution and the regulation of IDT production in various fungi and compare the organization of the known IDT biosynthetic gene clusters. A detailed assessment of the highly diverse biological activities of these mycotoxins leads us to emphasize the significant losses that paspaline-derived IDTs cause in agriculture, and compels us to warn about the various hazards they represent towards human and livestock health. Conversely, we also describe the potential utility of these versatile molecules as lead compounds for pharmaceutical drug discovery, and examine the prospects for their industrial scale manufacture in genetically manipulated IDT producers or domesticated host microorganisms in synthetic biological production systems.