Dipartimento di Biologia Vegetale, Università "Sapienza", L.go Cristina di Svezia 24, 00165 Roma, Italy.
Appl Microbiol Biotechnol. 2010 Feb;85(6):1935-46. doi: 10.1007/s00253-009-2220-4. Epub 2009 Sep 26.
In Aspergillus nidulans, Aspergillus flavus, and Aspergillus parasiticus, lipoperoxidative signalling is crucial for the regulation of mycotoxin biosynthesis, conidiogenesis, and sclerotia formation. Resveratrol, which is a lipoxygenase (LOX) and cyclooxygenase inhibitor, downmodulates the biosynthesis of ochratoxin A (OTA) in Aspergillus ochraceus. In the genome of A. ochraceus, a lox-like sequence (AoloxA; National Center for Biotechnology Information (NCBI) accession number: DQ087531) for a lipoxygenase-like enzyme has been found, which presents high homology (100 identities, 100 positives %, score 555) with a lox gene of Aspergillus fumigatus (NCBI accession number: XM741370). To study how inhibition of oxylipins formation may affect the A. ochraceus metabolism, we have used a DeltaAoloxA strain. This mutant displays a different colony morphology, a delayed conidia formation, and a high sclerotia production. When compared to the wild type, the DeltaAoloxA strain showed a lower basal activity of LOX and diminished levels of 13-hydroperoxylinoleic acid (HPODE) and other oxylipins derived from linoleic acid. The limited oxylipins formation corresponded to a remarkable inhibition of OTA biosynthesis in the DeltaAoloxA strain. Also, wheat seeds (Triticum durum cv Ciccio) inoculated with the DeltaAoloxA mutant did not accumulate 9-HPODE, which is a crucial element in the host defence system. Similarly, the expression of the pathogenesis-related protein 1 (PR1) gene in wheat seeds was not enhanced. The results obtained contribute to the current knowledge on the role of lipid peroxidation governed by the AoloxA gene in the morphogenesis, OTA biosynthesis, and in host-pathogen interaction between wheat seeds and A. ochraceus.
在构巢曲霉、黄曲霉和寄生曲霉中，脂氧合酶（LOX）和环氧化酶抑制剂花生四烯酸脂氧合酶信号通路对于调控真菌毒素生物合成、分生孢子发生和产黑色素体形成至关重要。白藜芦醇是一种脂氧合酶（LOX）和环氧化酶抑制剂，可下调赭曲霉中赭曲霉毒素 A（OTA）的生物合成。在赭曲霉基因组中，发现了一个类似于脂氧合酶的序列（AoloxA；美国国家生物技术信息中心（NCBI）登录号：DQ087531），该序列与烟曲霉的lox 基因（NCBI 登录号：XM741370）具有高度同源性（100 个身份、100 个阳性、评分 555）。为了研究抑制脂氧合产物形成如何影响赭曲霉的代谢，我们使用了ΔAoloxA 突变株。该突变株表现出不同的菌落形态、延迟分生孢子形成和产黑色素体增加。与野生型相比，ΔAoloxA 菌株的 LOX 基础活性较低，13-羟基亚麻酸（HPODE）和其他来源于亚麻酸的脂氧合产物水平降低。有限的脂氧合产物形成对应于ΔAoloxA 菌株中 OTA 生物合成的显著抑制。此外，用ΔAoloxA 突变株接种的小麦种子（硬粒小麦 cv Ciccio）未积累 9-HPODE，而 9-HPODE 是宿主防御系统中的关键元素。同样，小麦种子中病程相关蛋白 1（PR1）基因的表达也没有增强。这些结果有助于了解由 AoloxA 基因控制的脂质过氧化在形态发生、OTA 生物合成以及小麦种子与赭曲霉之间的宿主-病原体相互作用中的作用。
