USDA-ARS, Crop Protection and Management Research Unit, Tifton, GA, 31793, USA.
Department of Plant Pathology, University of Georgia, Tifton, GA, 31793, USA.
BMC Microbiol. 2019 Sep 5;19(1):209. doi: 10.1186/s12866-019-1580-x.
The primary and secondary metabolites of fungi are critical for adaptation to environmental stresses, host pathogenicity, competition with other microbes, and reproductive fitness. Drought-derived reactive oxygen species (ROS) have been shown to stimulate aflatoxin production and regulate in Aspergillus flavus, and may function in signaling with host plants. Here, we have performed global, untargeted metabolomics to better understand the role of aflatoxin production in oxidative stress responses, and also explore isolate-specific oxidative stress responses over time.
Two field isolates of A. flavus, AF13 and NRRL3357, possessing high and moderate aflatoxin production, respectively, were cultured in medium with and without supplementation with 15 mM HO, and mycelia were collected following 4 and 7 days in culture for global metabolomics. Overall, 389 compounds were described in the analysis which encompassed 9 biological super-pathways and 47 sub-pathways. These metabolites were examined for differential accumulation. Significant differences were observed in both isolates in response to oxidative stress and when comparing sampling time points.
The moderately high aflatoxin-producing isolate, NRRL3357, showed extensive stimulation of antioxidant mechanisms and pathways including polyamines metabolism, glutathione metabolism, TCA cycle, and lipid metabolism while the highly aflatoxigenic isolate, AF13, showed a less vigorous response to stress. Carbohydrate pathway levels also imply that carbohydrate repression and starvation may influence metabolite accumulation at the later timepoint. Higher conidial oxidative stress tolerance and antioxidant capacity in AF13 compared to NRRL3357, inferred from their metabolomic profiles and growth curves over time, may be connected to aflatoxin production capability and aflatoxin-related antioxidant accumulation. The coincidence of several of the detected metabolites in HO-stressed A. flavus and drought-stressed hosts also suggests their potential role in the interaction between these organisms and their use as markers/targets to enhance host resistance through biomarker selection or genetic engineering.
真菌的初级和次级代谢产物对于适应环境压力、宿主致病性、与其他微生物竞争和生殖适应性至关重要。已证明干旱产生的活性氧（ROS）可刺激黄曲霉产黄曲霉毒素并调节黄曲霉产黄曲霉毒素，并且可能在与宿主植物的信号转导中发挥作用。在这里，我们进行了全局、非靶向代谢组学研究，以更好地了解黄曲霉毒素产生在氧化应激反应中的作用，并随着时间的推移探索分离株特有的氧化应激反应。
两种田间分离的黄曲霉，AF13 和 NRRL3357，分别具有高产黄曲霉毒素和中产黄曲霉毒素的能力，在含有和不含有 15mM HO 的培养基中培养，并在培养 4 天和 7 天后收集菌丝体进行全局代谢组学分析。总体而言，分析中描述了 389 种化合物，涵盖了 9 个生物超级途径和 47 个亚途径。检查了这些代谢物的差异积累。在两种分离株中都观察到了氧化应激和采样时间点的显著差异。
中高产黄曲霉毒素的分离株 NRRL3357 表现出广泛的抗氧化机制和途径的刺激，包括多胺代谢、谷胱甘肽代谢、三羧酸循环和脂质代谢，而高产黄曲霉毒素的分离株 AF13 对压力的反应较弱。碳水化合物途径水平也表明，碳水化合物抑制和饥饿可能会影响后期时间点的代谢物积累。AF13 比 NRRL3357 具有更高的分生孢子氧化应激耐受性和抗氧化能力，这可以从它们的代谢组学图谱和随时间的生长曲线推断得出，这可能与黄曲霉毒素产生能力和与黄曲霉毒素相关的抗氧化剂积累有关。在 HO 胁迫的黄曲霉和干旱胁迫的宿主中检测到的几种代谢物的巧合也表明它们在这些生物体之间的相互作用中的潜在作用，并可以作为通过生物标志物选择或遗传工程提高宿主抗性的标志物/靶标。
