Characterization of the Far Transcription Factor Family in Aspergillus flavus.
Characterization of the Far Transcription Factor Family in Aspergillus flavus.
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DOI：
10.1534/g3.116.032466
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发表时间：
2016-10-13
期刊：
影响因子：
--
通讯作者：
Keller NP
中科院分区：
文献类型：
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作者：
Luo X;Affeldt KJ;Keller NP
脂肪酸的代谢是油籽致病菌（包括真菌黄曲霉）发病的关键条件。以前的研究表明，这种真菌在脂肪酸上生长的能力下降与对宿主种子的毒力降低有关。两种脂肪酸代谢调节转录因子，FarA和FarB，已经在其他丝状真菌中被描述。出乎意料的是，我们发现a . flavus具有三个Far同源物，FarA， FarB和FarC，其中FarA和FarC比FarB具有更大的蛋白质相似性。farA和farB在迄今测序的所有曲霉属中位于共线性区域，而farC则局限于一小部分物种，其插入曲霉基因组中其他共线性区域。farA和farB的缺失和过表达（OE），而不是farC，产生了特定脂肪酸生长模式异常的突变体，以及参与脂肪酸代谢的基因表达改变。显著差异包括中链脂肪酸的∆farA和∆farB生长缺陷显著，不饱和脂肪酸的OE::farA生长下降。farA的缺失减少了线粒体β-氧化基因的表达，而OE::farA抑制了参与不饱和脂肪酸分解代谢的基因的表达。FarA还积极调节产生多不饱和脂肪酸所需的去饱和酶基因。在诱毒培养基上，∆farB突变体的黄曲霉毒素产量显著降低，而OE::farB突变体的黄曲霉毒素产量显著增加，基因表达数据支持farB在β-氧化过程与黄曲霉毒素积累之间起作用。
Metabolism of fatty acids is a critical requirement for the pathogenesis of oil seed pathogens including the fungus Aspergillus flavus. Previous studies have correlated decreased ability to grow on fatty acids with reduced virulence of this fungus on host seed. Two fatty acid metabolism regulatory transcription factors, FarA and FarB, have been described in other filamentous fungi. Unexpectedly, we find A. flavus possesses three Far homologs, FarA, FarB, and FarC, with FarA and FarC showing a greater protein similarity to each other than FarB. farA and farB are located in regions of colinearity in all Aspergillus spp. sequenced to date, whereas farC is limited to a subset of species where it is inserted in an otherwise colinear region in Aspergillus genomes. Deletion and overexpression (OE) of farA and farB, but not farC, yielded mutants with aberrant growth patterns on specific fatty acids as well as altered expression of genes involved in fatty acid metabolism. Marked differences included significant growth defects of both ∆farA and ∆farB on medium-chain fatty acids and decreased growth of OE::farA on unsaturated fatty acids. Loss of farA diminished expression of mitochondrial β-oxidation genes whereas OE::farA inhibited expression of genes involved in unsaturated fatty acid catabolism. FarA also positively regulated the desaturase genes required to generate polyunsaturated fatty acids. Aflatoxin production on toxin-inducing media was significantly decreased in the ∆farB mutant and increased in the OE::farB mutant, with gene expression data supporting a role for FarB in tying β-oxidation processes with aflatoxin accumulation.