Reverberi Massimo, Zjalic Slaven, Ricelli Alessandra, Punelli Federico, Camera Emanuela, Fabbri Claudia, Picardo Mauro, Fanelli Corrado, Fabbri Anna A
Dipartimento di Biologia Vegetale, Università La Sapienza, Largo Cristina di Svezia 24, 00165 Roma, Italy.
Eukaryot Cell. 2008 Jun;7(6):988-1000. doi: 10.1128/EC.00228-07. Epub 2008 Apr 25.
Oxidative stress is recognized as a trigger of different metabolic events in all organisms. Various factors correlated with oxidation, such as the beta-oxidation of fatty acids and their enzymatic or nonenzymatic by-products (e.g., precocious sexual inducer factors and lipoperoxides) have been shown to be involved in aflatoxin formation. In the present study, we found that increased levels of reactive oxygen species (ROS) were correlated with increased levels of aflatoxin biosynthesis in Aspergillus parasiticus. To better understand the role of ROS formation in toxin production, we generated a mutant (Delta ApyapA) having the ApyapA gene deleted, given that ApyapA orthologs have been shown to be part of the antioxidant response in other fungi. Compared to the wild type, the mutant showed an increased susceptibility to extracellular oxidants, as well as precocious ROS formation and aflatoxin biosynthesis. Genetic complementation of the Delta ApyapA mutant restored the timing and quantity of toxin biosynthesis to the levels found in the wild type. The presence of putative AP1 (ApYapA orthologue) binding sites in the promoter region of the regulatory gene aflR further supports the finding that ApYapA plays a role in the regulation of aflatoxin biosynthesis. Overall, our results show that the lack of ApyapA leads to an increase in oxidative stress, premature conidiogenesis, and aflatoxin biosynthesis.
氧化应激被认为是所有生物体中不同代谢事件的触发因素。各种与氧化相关的因素，如脂肪酸的β-氧化及其酶促或非酶促副产物（如早熟性诱导因子和脂过氧化物）已被证明与黄曲霉毒素的形成有关。在本研究中，我们发现寄生曲霉中活性氧（ROS）水平的升高与黄曲霉毒素生物合成水平的增加相关。为了更好地理解ROS形成在毒素产生中的作用，我们构建了一个缺失ApyapA基因的突变体（ΔApyapA），因为已证明ApyapA直系同源物是其他真菌抗氧化反应的一部分。与野生型相比，该突变体对细胞外氧化剂的敏感性增加，同时ROS形成过早且黄曲霉毒素生物合成增加。ΔApyapA突变体的基因互补将毒素生物合成的时间和数量恢复到野生型水平。调控基因aflR启动子区域中假定的AP1（ApYapA直系同源物）结合位点的存在进一步支持了ApYapA在黄曲霉毒素生物合成调控中起作用的这一发现。总体而言，我们的结果表明，ApyapA的缺失导致氧化应激增加、分生孢子过早形成以及黄曲霉毒素生物合成增加。
