Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1QW, UK.
Environ Microbiol. 2010 Jul;12(7):1811-27. doi: 10.1111/j.1462-2920.2010.02170.x. Epub 2010 Feb 26.
Pectobacterium carotovorum SCRI193 is a phytopathogenic Gram-negative bacterium. In this study, we have identified a novel cryptic pigment biosynthetic locus in P. carotovorum SCRI193 which we have called the Pectobacterium orange pigment (pop) cluster. The pop cluster is flanked by two tRNA genes and contains genes that encode non-ribosomal peptide synthases and polyketide synthase and produces a negatively charged polar orange pigment. Orange pigment production is activated when an adjacent transcriptional activator sharing sequence similarity with the Erwinia virulence regulator (Evr) is overexpressed. Evr was shown to positively activate its own transcription and that of the pigment biosynthetic genes and an unlinked locus encoding a phenomycin homologue. In addition, the expression of Evr and orange pigment production was shown to be regulated by N-(3-oxohexanoyl)-HSL (OHHL) quorum sensing and have a virulence phenotype in potato. Finally, by comparative genomics and Southern blotting we demonstrate that this pigment biosynthetic cluster is present in multiple P. carotovorum spp., Pectobacterium brasiliensis 1692 and a truncated version of the cluster is present in Pectobacterium atrosepticum. The conserved nature of this cluster in P. carotovorum and P. brasiliensis suggests that the pop cluster has an important function in these broad-host-range soft rotting bacteria, which is no longer required in the narrow-host-range P. atrosepticum SCRI1043.
果胶杆菌 SCRI193 是一种植物病原革兰氏阴性细菌。在本研究中,我们在果胶杆菌 SCRI193 中鉴定出一个新的隐性色素生物合成基因座,我们将其称为果胶杆菌橙色色素(pop)簇。pop 簇由两个 tRNA 基因侧翼,并包含编码非核糖体肽合酶和聚酮合酶的基因,并产生带负电荷的极性橙色色素。当相邻的转录激活因子与欧文氏菌毒力调节因子(Evr)具有序列相似性时,橙色色素的产生被激活。研究表明,Evr 可以正向激活其自身的转录以及色素生物合成基因和编码青霉素类似物的非连锁基因座的转录。此外,Evr 的表达和橙色色素的产生受到 N-(3-氧代己酰基)-HSL (OHHL) 群体感应的调节,并在马铃薯中有致病表型。最后,通过比较基因组学和 Southern 印迹分析,我们证明了这个色素生物合成簇存在于多种果胶杆菌 spp.、巴西果胶杆菌 1692 中,并且在果胶杆菌 atrosepticum 中存在该簇的截断版本。该簇在果胶杆菌和巴西果胶杆菌中的保守性表明,pop 簇在这些广泛宿主范围的软腐细菌中具有重要功能,而在狭窄宿主范围的果胶杆菌 atrosepticum SCRI1043 中不再需要该功能。