植物と微生物の関係をパトロールする真菌の「用心棒」Fungal ‘bouncers’ patrol plant-microbe relationship

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2024-01-17 オークリッジ国立研究所(ORNL)

◆米国エネルギー省のオークリッジ国立研究所(ORNL)の研究者は、土壌マイクロバイオームにおいて植物を保護するキノコの特化した代謝物に焦点を当てる計算フレームワークを開発しました。
◆グラフ理論を使用したデータ駆動の手法を利用し、キノコが生成する特化した代謝物の生産に影響を与える化合物や環境ストレスを分析しました。これにより、特化した代謝物の同定が迅速化され、これらの代謝物の植物への影響を理解するための大規模で効果的な方法が提供されました。
◆研究は、植物と微生物の相互関係を探求するORNLのPlant-Microbe Interfaces Scientific Focus Areaプロジェクトの一環で、土壌の生態系におけるバイオエネルギー生産、環境浄化、土壌炭素貯蔵に関連する課題に取り組んでいます。

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真菌のメタボロミクスの深淵を垣間見る:新規ネットワーク解析により外因性化合物とそのアウトプットとの関係が明らかになる A glimpse into the fungal metabolomic abyss: Novel network analysis reveals relationships between exogenous compounds and their outputs

Muralikrishnan Gopalakrishnan Meena, Matthew J Lane, Joanna Tannous, Alyssa A Carrell, Paul E Abraham, Richard J Giannone, Jean-Michel Ané, Nancy P Keller, Jesse L Labbé, Armin G Geiger,David Kainer, Daniel A Jacobson, Tomás A Rush
PNAS Nexus  Published:29 September 2023
DOI:https://doi.org/10.1093/pnasnexus/pgad322

Framework of the direct and auxiliary routes using experimental inputs and implications for postanalysis applications. An overview of the network analysis approach reveals the effect of exogenous compounds on triggering the production of microbial specialized metabolites. In our experimental design, the data are obtained after exposing A. fumigatus to various abiotic or biotic factors for specific time points. The fungal exudates are separated from the fungal biomass, extracted through a filter membrane, homogenized with an organic solvent (ethyl acetate), and separated from the aqueous phase, dried, and resuspended in acetonitrile and water (50:50) (v/v). These samples were later processed through ultra-high pressure liquid chromatography-mass spectrometry (UHPLC-MS), which provides spectra data. Next, the spectra data are analyzed through XCMS and curated to retain only significant analytes with a P-value <0.05 and a log2 fold change >1.0 or <-1.0. The data are represented in volcano plots, which is standard practice to display differences of metabolite production between treated samples and the control. To develop our novel method, we used the log2 fold change data points for the network analysis that quantitatively represent the effect of exogenous treatments to trigger specialized metabolites. The treatments and metabolomic outputs are ranked by using network analysis measures through our two new methods: the direct route and the auxiliary route. The direct route is used to understand the influence of treatment on known or putative metabolites. MAVEN was used to identify and match the peak intensity, m/z, and retention time of known or putative metabolites previously described or predicted in A. fumigatus. Known metabolites were also confirmed through fragmentation patterns or in silico spiking with a commercial standard. Because spectra data can have baseline creeping, which causes peak noise and could influence the peak intensity, we further curated the spectra data to eliminate these artifacts to develop the auxiliary route. This route is used to identify strong signals of unknown analytes and screen with public databases such as KEGG or Lipid Maps to find known metabolites from other organisms that have not been described in A. fumigatus. After knowing the relationship between a treatment and metabolomic outputs, postanalysis applications can be applied to isolate and characterize the metabolite through genetic manipulations followed by bioactivity screening. These two postanalysis applications are provided as guidance on possible applications of the current framework for discovering new metabolites and are not performed in the current study.

Abstract

Fungal specialized metabolites are a major source of beneficial compounds that are routinely isolated, characterized, and manufactured as pharmaceuticals, agrochemical agents, and industrial chemicals. The production of these metabolites is encoded by biosynthetic gene clusters that are often silent under standard growth conditions. There are limited resources for characterizing the direct link between abiotic stimuli and metabolite production. Herein, we introduce a network analysis-based, data-driven algorithm comprising two routes to characterize the production of specialized fungal metabolites triggered by different exogenous compounds: the direct route and the auxiliary route. Both routes elucidate the influence of treatments on the production of specialized metabolites from experimental data. The direct route determines known and putative metabolites induced by treatments and provides additional insight over traditional comparison methods. The auxiliary route is specific for discovering unknown analytes, and further identification can be curated through online bioinformatic resources. We validated our algorithm by applying chitooligosaccharides and lipids at two different temperatures to the fungal pathogen Aspergillus fumigatus. After liquid chromatography–mass spectrometry quantification of significantly produced analytes, we used network centrality measures to rank the treatments’ ability to elucidate these analytes and confirmed their identity through fragmentation patterns or in silico spiking with commercially available standards. Later, we examined the transcriptional regulation of these metabolites through real-time quantitative polymerase chain reaction. Our data-driven techniques can complement existing metabolomic network analysis by providing an approach to track the influence of any exogenous stimuli on metabolite production. Our experimental-based algorithm can overcome the bottlenecks in elucidating novel fungal compounds used in drug discovery.

リポキトオリゴ糖が細菌の増殖を制御する特殊な真菌代謝物プロファイルを誘導する Lipo-Chitooligosaccharides Induce Specialized Fungal Metabolite Profiles That Modulate Bacterial Growth

Tomás A. Rush, Joanna Tannous, Matthew J. Lane, Muralikrishnan Gopalakrishnan Meena, Alyssa A. Carrell, Jacob J. Golan, Milton T. Drott, Sylvain Cottaz, Sébastien Fort, Jean-Michel Ané, Nancy P. Keller, Dale A. Pelletier, Daniel A. Jacobson, David Kainer, Paul E. Abraham, Richard J. Giannone, Jesse L. Labbé
mSystems  Published:1 December 2022
DOI:https://doi.org/10.1128/msystems.01052-22

ABSTRACT

Lipo-chitooligosaccharides (LCOs) are historically known for their role as microbial-derived signaling molecules that shape plant symbiosis with beneficial rhizobia or mycorrhizal fungi. Recent studies showing that LCOs are widespread across the fungal kingdom have raised questions about the ecological function of these compounds in organisms that do not form symbiotic relationships with plants. To elucidate the ecological function of these compounds, we investigate the metabolomic response of the ubiquitous human pathogen Aspergillus fumigatus to LCOs. Our metabolomics data revealed that exogenous application of various types of LCOs to A. fumigatus resulted in significant shifts in the fungal metabolic profile, with marked changes in the production of specialized metabolites known to mediate ecological interactions. Using network analyses, we identify specific types of LCOs with the most significant effect on the abundance of known metabolites. Extracts of several LCO-induced metabolic profiles significantly impact the growth rates of diverse bacterial species. These findings suggest that LCOs may play an important role in the competitive dynamics of non-plant-symbiotic fungi and bacteria. This study identifies specific metabolomic profiles induced by these ubiquitously produced chemicals and creates a foundation for future studies into the potential roles of LCOs as modulators of interkingdom competition.

IMPORTANCE The activation of silent biosynthetic gene clusters (BGC) for the identification and characterization of novel fungal secondary metabolites is a perpetual motion in natural product discoveries. Here, we demonstrated that one of the best-studied symbiosis signaling compounds, lipo-chitooligosaccharides (LCOs), play a role in activating some of these BGCs, resulting in the production of known, putative, and unknown metabolites with biological activities. This collection of metabolites induced by LCOs differentially modulate bacterial growth, while the LCO standards do not convey the same effect. These findings create a paradigm shift showing that LCOs have a more prominent role outside of host recognition of symbiotic microbes. Importantly, our work demonstrates that fungi use LCOs to produce a variety of metabolites with biological activity, which can be a potential source of bio-stimulants, pesticides, or pharmaceuticals.

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