Oxygenase Coordination Is Required for Morphological Transition and the Host-Fungus Interaction of Aspergillus flavus
Oxygenase Coordination Is Required for Morphological Transition and the Host-Fungus Interaction of Aspergillus flavus
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DOI：
10.1094/mpmi-22-7-0882
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发表时间：
2009-07-01
影响因子：
3.5
通讯作者：
Keller, Nancy P.
中科院分区：
文献类型：
--
作者：
Brown, Sigal Horowitz;Scott, James B.;Keller, Nancy P.
氧脂素是一类由加氧酶产生的不饱和脂肪酸，是许多生物系统中重要的信号分子。黄曲霉脂氧合酶基因，脂氧合酶，最近的表征，揭示了其重要性，在保持密度依赖性的形态开关从菌核分生孢子人口密度的增加。在这里，我们提出的证据涉及四个氧化脂生成双加氧酶（PpoA，PpoB，PpoC和PpoD）在A。黄曲霉密度依赖现象和这些基因的损失对黄曲霉毒素生产和种子定殖的影响。虽然几个单一的突变体表现出改变，在菌核分生孢子开关，主要的影响是观察到的所有五个加氧酶下调的菌株（反向重复转基因[IRT]菌株IRT 4 = ppoA，ppoB，ppoC，ppoD，和lox）。在菌株IRT 4中，菌核产生增加至500倍，而分生孢子减少至100倍，并且该菌株不能切换成分生孢子产生。所有突变株和野生型的黄曲霉毒素（AF）产量在低人口密度下最大，而在高人口密度下则不存在，但菌株IRT 4除外，该菌株始终产生高水平的真菌毒素。IRT 4和IRT 2（在ppoA、ppoB和ppoD中下调）在宿主种子上的生长以减少分生孢子但增加AF产生为标志。我们建议A.黄加氧酶和它们产生的氧脂在高度相互依赖的网络中起作用，具有一些冗余的生物学功能。这些研究为基于氧化脂素的真菌-种子相互作用机制和调节A.黄的
Oxylipins, a class of oxygenase-derived unsaturated fatty acids, are important signal molecules in many biological systems. Recent characterization of an Aspergillus flavus lipoxygenase gene, lox, revealed its importance in maintaining a density-dependent morphology switch from sclerotia to conidia as population density increased. Here, we present evidence for the involvement of four more oxylipin-generating dioxygenases (PpoA, PpoB, PpoC, and PpoD) in A. flavus density-dependent phenomena and the effects of loss of these genes on aflatoxin production and seed colonization. Although several single mutants showed alterations in the sclerotia-to-conidia switch, the major effect was observed in a strain downregulated for all five oxygenases (invert repeat transgene [IRT] strain IRT4 = ppoA, ppoB, ppoC, ppoD, and lox). In strain IRT4, sclerotia production was increased up to 500-fold whereas conidiation was decreased down to 100-fold and the strain was unable to switch into conidial production. Aflatoxin (AF) production for all mutant strains and the wild type was greatest at low population densities and absent in high populations except for strain IRT4, which consistently produced high levels of the mycotoxin. Growth on host seed by both IRT4 and IRT2 (downregulated in ppoA, ppoB, and ppoD) was marked by decreased conidial but increased AF production. We propose that A. flavus oxygenases and the oxylipins they produce act in a highly interdependent network with some redundancy of biological function. These studies provide substantial evidence for oxylipin- based mechanisms in governing fungus-seed interactions and in regulating a coordinated quorum-sensing mechanism in A. flavus.