| 描述信息 |
Momilactones are bioactive diterpenoids that contribute to plant defense against pathogens and allelopathic interactions between plants. Both cultivated and wild grass species of genus Oryza and Echinochloa crus-galli (barnyardgrass) produce momilactones using a biosynthetic gene cluster in their genomes. The bryophyte Hypnum plumaeforme has also been shown to produce momilactones, and the bifunctional diterpene cyclase gene HpDTC1, which is responsible for the production of the diterpene framework, has been characterized. To understand the molecular architecture of the momilactone biosynthetic genes in the moss genome and their evolutionary relationships with other momilactone producing plants, we sequenced and annotated the H. plumaeforme genome. These data revealed a 150 Kb genomic region that contains two cytochrome P450 genes, the HpDTC1 gene, and the dehydrogenase momilactone A synthase gene tandemly arranged. The predicted enzymatic functions and stress inducibility of the clustered genes suggest that it is a functional biosynthetic gene cluster responsible for momilactone production. In a survey of genomic sequences encompassing a broad range of plant species, we also found that momilactone biosynthetic gene clusters are limited to the two grass species (Oryza and Echinochloa) and H. plumaeforme, and there is no synteny among these genomes. These results indicate that, while the gene cluster in H. plumaeforme is functionally similar to those in rice and barnyard grass, these clusters are likely a product of convergent evolution. This is, to our knowledge, the first report of a biosynthetic gene cluster for a specialized plant defense metabolite in bryophytes. |
