Department of Plant Pathology, Washington State University, Pullman, WA 99164-6430, USA.
Curr Genet. 2010 Aug;56(4):349-60. doi: 10.1007/s00294-010-0306-2. Epub 2010 May 16.
Ascochyta rabiei produces and accumulates one of the well-known fungal polyketides, 1,8-dihydroxynaphthalene-melanin pigment (DHN-melanin), in asexual and sexual fruiting bodies. Degenerate PCR primers were used to isolate an ArPKS1 of A. rabiei encoding a polypeptide with high similarity to polyketide synthase (PKS) involved in biosynthesis of DHN-melanin in other ascomycetous fungi. Site-directed mutagenesis of ArPKS1 in A. rabiei generated melanin-deficient pycnidial mutants but caused no significant reduction of pathogenicity to chickpea. Pycnidiospores in ArPKS1-mutant pycnidia showed higher sensitivity to UV light exposure compared to pycnidiospores in melanized pycnidia of the wild-type progenitor isolate. Integration of an orthologous PKS1 gene from Bipolaris oryzae into the genome of the mutants complemented the dysfunctional ArPKS1 gene. This study demonstrated that A. rabiei uses a DHN-melanin pathway for pigmentation of pycnidia and this molecule may protect pycnidiospores from UV irradiation.
罗伯茨曲霉（Ascochyta rabiei）在无性和有性生殖体中产生并积累一种著名的真菌聚酮化合物，1,8-二羟基萘黑色素（DHN-黑色素）。使用简并 PCR 引物从罗伯茨曲霉中分离出一个编码与其他子囊菌中参与 DHN-黑色素生物合成的聚酮合酶（PKS）具有高度相似性的多肽的 ArPKS1。在罗伯茨曲霉中对 ArPKS1 进行定点诱变产生了黑色素缺陷的分生孢子器突变体，但对鹰嘴豆的致病性没有显著降低。与野生型亲代分离物中黑色素化分生孢子器中的分生孢子相比，ArPKS1 突变体分生孢子器中的分生孢子对紫外线照射表现出更高的敏感性。将来自稻生双极霉（Bipolaris oryzae）的同源 PKS1 基因整合到突变体的基因组中，可弥补功能失调的 ArPKS1 基因。这项研究表明，罗伯茨曲霉使用 DHN-黑色素途径对分生孢子进行着色，并且这种分子可能保护分生孢子免受紫外线照射。
