Studies on the diversity of graminicolous Helminthosporium species by DNA analyzes and its taxonomical application

对异养蜗黑色素的生物合成途径进行了分析。克隆并测序了参与黑色素生物合成的还原酶基因Brn1基因。Brn基因包含一个开放阅读框（804bp），由两个内含子分隔的3个外显子组成，预测的Brn1多肽由267个氨基酸组成。该基因在该真菌的每个基因组中只包含一个拷贝。利用该基因分析了禾草属Helminthosporium、Bipolaris、Curvularia、Drechslera、exserhilum的分类关系。以异养蜗（Cochliobolus heterostrophus）的部分序列为引物，扩增了4属部分成员的Brn1基因。这些序列的比对结果显示，除了内含子区域外，整个序列都具有高度的相似性。邻域连接分析利用这些序列构建了4个聚类。进化图很好地反映了该基因在这些属中的分化。然而，这四个属之间的关系与基于形态特征的关系有所不同。对植物病原真菌的相关研究进行了综述。

The melanin biosynthetic pathway of Cochliobolus heterostrophus was analyzed. The Brn1 gene coding for reductase gene involved in melanin biosynthesis was cloned and sequenced. The Brn gene contains one open reading frame (804bp), consisting of 3 exons separated by two introns, and the predicted Brn1 polypeptide consists of 267 amno acids. The gene was contained only one copy per genome in this fungus.By using this gene, the taxonomical relationships in so-called graminicolous Helminthosporium species, Bipolaris, Curvularia, Drechslera, Exserohilum were analyzed. The Brn1 gene of some selected members in four genera was amplified with partial sequences derived from that of Cochliobolus heterostrophus as primers in PCR anc sequenced. Alignment of these sequences showed high similarities to each other through the entire sequence but intron regions.Neibour joining analysis using these sequences constructed four clusters. The cladogram well reflected the differentiation in this gene within these genera. However, relationships within these four genera differ from thosew based on morphological characters.Some other related studies on the plant pathogenic fungi were also summarized here.