Rice-induced secondary metabolite gene expression in Aspergillus nidulans
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NATURAL PRODUCTS - ORIGINAL PAPER
Rice‑induced secondary metabolite gene expression in Aspergillus nidulans Christopher J. Lacriola1 · Shaun P. Falk1 · Bernard Weisblum1 Received: 26 August 2020 / Accepted: 2 November 2020 © Society for Industrial Microbiology and Biotechnology 2020
Abstract Activation of silent biosynthetic gene clusters in fungi remains a challenge for discovery of new useful natural products. In this work, we identify a group of silent secondary metabolite gene clusters in Aspergillus nidulans that are induced by rice (Oryza sativa). Using reverse phase HPLC purification on extracts of rice, we identified the plant hormone gibberellic acid as one compound present in rice extracts that induced these silent genes. Additionally, select secondary metabolite (SM) genes activated by rice were tested for responses to several plant hormones which produced distinctly different transcriptomic profiles in A. nidulans. These observations support the idea that phytohormones play an important role in regulating fungal SM biosynthesis while additionally serving as a source of natural product chemical libraries to screen for useful compounds.
Introduction Fungi have the potential to synthesize a wide range of biologically active compounds that are important for medicine, industry, and agriculture. This potential is not fully realized since many fungal genes and their secondary metabolite (SM) products are either silent or synthesized at a level well below the threshold of detection when grown under standard laboratory conditions [15]. Further complicating the expression of SMs is the complex system of regulation of fungal SM genes. These regulatory mechanisms include global and cluster-specific regulators, epigenetic factors and signal transduction pathways. Previous studies focused on utilizing genomic modification to alter the secondary metabolome [1, 2, 9, 10]. For reviews, see Chiang et al. [5] and Macheleidt et al. [23]. Co-culture has been widely used as an alternative to targeted gene modification to induce SMs in microorganisms [3]. Specifically, co-cultures commonly consist of two or more microbial strains, or, less commonly, a plant–microbe Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10295-020-02328-x) contains supplementary material, which is available to authorized users. * Christopher J. Lacriola [email protected] 1
Department of Medicine, School of Medicine and Public Health, University of Wisconsin Madison, Madison, WI 53706, USA
combination, grown together. Aspergilli commonly colonize rice and other staple crops as part of an endophytic relationship that can induce the production of antibiotics, immunosuppressants, phytotoxins, and other biologically active SMs of interest [27]. Despite the large number of chemical mediators of plant-fungal interactions proposed [18, 28], research has primarily focused on the effect of the fungal metabolites on the plant in respect to food spoilage and pathogenesis. Fewer studies have examined the
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