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Abstract：
Cinnamic acid is an aromatic compound commonly found in plants and functions as a central intermediate in lignin synthesis. Filamentous fungi are able to degrade cinnamic acid through multiple metabolic pathways. One of the best studied pathways is the non-oxidative decarboxylation of cinnamic acid to styrene. In Aspergillus niger, the enzymes cinnamic acid decarboxylase (CdcA, formally ferulic acid decarboxylase) and the flavin prenyltransferase (PadA) catalyze together the non-oxidative decarboxylation of cinnamic acid and sorbic acid. The corresponding genes, cdcA and padA, are clustered in the genome together with a putative transcription factor previously named sorbic acid decarboxylase regulator (SdrA). While SdrA was predicted to be involved in the regulation of the non-oxidative decarboxylation of cinnamic acid and sorbic acid, this was never functionally analyzed. In this study, A. niger deletion mutants of sdrA, cdcA, and padA were made to further investigate the role of SdrA in cinnamic acid metabolism. Phenotypic analysis revealed that cdcA, sdrA and padA are exclusively involved in the degradation of cinnamic acid and sorbic acid and not required for other related aromatic compounds. Whole genome transcriptome analysis of ΔsdrA grown on different cinnamic acid related compounds, revealed additional target genes, which were also clustered with cdcA, sdrA, and padA in the A. niger genome. Synteny analysis using 30 Aspergillus genomes demonstrated a conserved cinnamic acid decarboxylation gene cluster in most Aspergilli of the Nigri clade. Aspergilli lacking certain genes in the cluster were unable to grow on cinnamic acid, but could still grow on related aromatic compounds, confirming the specific role of these three genes for cinnamic acid metabolism of A. niger.
摘要：
肉桂酸是植物中常见的芳香族化合物,并且在木质素合成中起中心中间体的作用。丝状真菌能够通过多种代谢途径降解肉桂酸。研究得最好的途径之一是肉桂酸非氧化脱羧成苯乙烯。在黑曲霉中，酶肉桂酸脱羧酶(CdcA，正式的阿魏酸脱羧酶）和黄素异戊二烯基转移酶（PadA）一起催化肉桂酸和山梨酸的非氧化脱羧。相应的基因，cdcA和padA,与先前称为山梨酸脱羧酶调节因子（SdrA）的推定转录因子一起聚集在基因组中。虽然预测SdrA参与肉桂酸和山梨酸的非氧化脱羧的调节，这从未进行过功能分析。在这项研究中,A.sdrA的尼日尔缺失突变体，cdcA,进一步研究了SdrA在肉桂酸代谢中的作用。表型分析显示，cdcA，sdrA和padA仅参与肉桂酸和山梨酸的降解，而不是其他相关的芳族化合物所必需的。在不同肉桂酸相关化合物上生长的ΔsdrA的全基因组转录组分析，揭示了额外的目标基因，它们也被cdcA聚集在一起，sdra,和黑曲霉基因组中的padA。使用30个曲霉基因组进行的合成分析表明，在Nigri进化枝的大多数曲霉中，存在保守的肉桂酸脱羧基因簇。群集中缺乏某些基因的曲霉不能在肉桂酸上生长，但仍然可以在相关的芳香化合物上生长，证实了这三个基因对黑曲霉肉桂酸代谢的具体作用。
