Reimmann C, VanEtten H D
Department of Plant Pathology, University of Arizona, Tucson 85721.
Gene. 1994 Sep 2;146(2):221-6. doi: 10.1016/0378-1119(94)90296-8.
The ability to detoxify pisatin, a phytoalexin produced by garden pea (Pisum sativum), is controlled by a family of PDA (pisatin demethylating ability) genes in the phytopathogenic fungus Nectria haematococa, MP (mating population) VI. Six known PDA genes each encode characteristic levels of inducible enzyme activity and are associated with different degrees of virulence on pea. To elucidate the phenotypic differences associated with these genes, we have cloned and characterized the PDA6-1 gene which encodes a pisatin-detoxifying enzyme and we compare it to another PDA gene, PDAT9. Pisatin demethylation was measured in PDA6-1 transformants of Aspergillus nidulans and shown to be regulated by glucose. The deduced amino acid (aa) sequence of PDA6-1 was 90% identical to that of the cytochrome P-450 encoded by PDAT9, but lacked nine aa at the C terminus, which has been postulated to be a site involved in substrate binding. A 35-bp sequence present upstream of a third PDA gene, PDA1, which appears to be important for induction of PDA1 by pisatin, was conserved in PDAT9, but not in PDA6-1. We conclude that PDA6-1, which does not appear to contribute to the virulence of N. haematococa on pea, differs significantly from PDAT9, which is associated with high virulence.
对豌豆素（一种由豌豆（Pisum sativum）产生的植物抗毒素）进行解毒的能力，由植物致病真菌血座壳菌（Nectria haematococa）MP（交配群体）VI中的一组PDA（豌豆素脱甲基化能力）基因控制。六个已知的PDA基因各自编码不同水平的诱导酶活性，并与对豌豆的不同毒力程度相关。为了阐明与这些基因相关的表型差异，我们克隆并鉴定了编码豌豆素解毒酶的PDA6 - 1基因，并将其与另一个PDA基因PDAT9进行比较。在构巢曲霉（Aspergillus nidulans）的PDA6 - 1转化体中测量了豌豆素脱甲基化情况，并表明其受葡萄糖调节。PDA6 - 1推导的氨基酸（aa）序列与PDAT9编码的细胞色素P - 450的序列有90%的同一性，但在C末端缺少九个氨基酸，据推测这是一个参与底物结合的位点。在第三个PDA基因PDA1上游存在的一个35 bp序列，似乎对豌豆素诱导PDA1很重要，该序列在PDAT9中保守，但在PDA6 - 1中不保守。我们得出结论，似乎对血座壳菌对豌豆的毒力没有贡献的PDA6 - 1，与与高毒力相关的PDAT9有显著差异。
