Responses of Aspergillus flavus to Oxidative Stress Are Related to Fungal Development Regulator, Antioxidant Enzyme, and Secondary Metabolite Biosynthetic Gene Expression.
Responses of Aspergillus flavus to Oxidative Stress Are Related to Fungal Development Regulator, Antioxidant Enzyme, and Secondary Metabolite Biosynthetic Gene Expression.
复制标题
DOI：
10.3389/fmicb.2016.02048
复制
发表时间：
2016
影响因子：
5.2
通讯作者：
Guo B
中科院分区：
文献类型：
--
作者：
Fountain JC;Bajaj P;Nayak SN;Yang L;Pandey MK;Kumar V;Jayale AS;Chitikineni A;Lee RD;Kemerait RC;Varshney RK;Guo B
玉米和花生的黄曲霉感染以及随后的黄曲霉毒素污染对全球食品安全和人类健康构成威胁，并因干旱胁迫而加剧。干旱胁迫响应化合物如活性氧（ROS）与真菌胁迫响应信号和次生代谢物的产生有关，并能刺激黄曲霉毒素的体外生产。这些次生代谢物已被证明在土传真菌中具有多种功能，包括抗生素、对其他微生物的竞争性抑制和非生物胁迫缓解。此前，我们观察到黄曲霉菌株在氧化应激耐受性方面存在差异，这与黄曲霉毒素产生能力有关。为了更好地了解这些特异性氧化应激反应，我们使用RNA测序方法检测了黄曲霉毒素产生水平（NRRL3357、AF13和Tox4）不同的黄曲霉田间分离株对h2o2诱导的氧化应激的转录反应。这些分离株在添加不同水平H2O2的有利于黄曲霉毒素产生的培养基中培养。使用Illumina HiSeq平台对整个转录组进行测序，每个样本平均产生4043万个过滤后的成对端reads。然后将获得的转录组用于差异表达、基因本体、途径和共表达分析。产生较高水平黄曲霉毒素的分离株往往比产生较低水平的分离株表现出较少的差异表达基因。在增加的氧化应激反应中差异表达的基因包括抗氧化酶、初级代谢成分、抗生素相关基因以及黄曲霉毒素、黄曲霉霉和曲酸的次生代谢产物生物合成成分。真菌发育相关基因的表达，包括氨基苯甲酸酯降解基因和条件调节基因，被发现在增加的胁迫下受到调节。黄曲霉毒素合成基因和抗氧化酶基因在胁迫下也存在共表达，且与真菌生物量高度相关。这表明这些次生代谢物可能是黄曲霉氧化应激反应的一部分，与抗氧化酶基因表达和发育调控有关。
The infection of maize and peanut with Aspergillus flavus and subsequent contamination with aflatoxin pose a threat to global food safety and human health, and is exacerbated by drought stress. Drought stress-responding compounds such as reactive oxygen species (ROS) are associated with fungal stress responsive signaling and secondary metabolite production, and can stimulate the production of aflatoxin by A. flavus in vitro. These secondary metabolites have been shown to possess diverse functions in soil-borne fungi including antibiosis, competitive inhibition of other microbes, and abiotic stress alleviation. Previously, we observed that isolates of A. flavus showed differences in oxidative stress tolerance which correlated with their aflatoxin production capabilities. In order to better understand these isolate-specific oxidative stress responses, we examined the transcriptional responses of field isolates of A. flavus with varying levels of aflatoxin production (NRRL3357, AF13, and Tox4) to H2O2-induced oxidative stress using an RNA sequencing approach. These isolates were cultured in an aflatoxin-production conducive medium amended with various levels of H2O2. Whole transcriptomes were sequenced using an Illumina HiSeq platform with an average of 40.43 million filtered paired-end reads generated for each sample. The obtained transcriptomes were then used for differential expression, gene ontology, pathway, and co-expression analyses. Isolates which produced higher levels of aflatoxin tended to exhibit fewer differentially expressed genes than isolates with lower levels of production. Genes found to be differentially expressed in response to increasing oxidative stress included antioxidant enzymes, primary metabolism components, antibiosis-related genes, and secondary metabolite biosynthetic components specifically for aflatoxin, aflatrem, and kojic acid. The expression of fungal development-related genes including aminobenzoate degradation genes and conidiation regulators were found to be regulated in response to increasing stress. Aflatoxin biosynthetic genes and antioxidant enzyme genes were also found to be co-expressed and highly correlated with fungal biomass under stress. This suggests that these secondary metabolites may be produced as part of coordinated oxidative stress responses in A. flavus along with antioxidant enzyme gene expression and developmental regulation.