Papaleo Maria Cristiana, Russo Edda, Fondi Marco, Emiliani Giovanni, Frandi Antonio, Brilli Matteo, Pastorelli Roberta, Fani Renato
Department of Evolutionary Biology, University of Florence, 50125 Florence, Italy.
Gene. 2009 Dec 1;448(1):16-28. doi: 10.1016/j.gene.2009.08.002. Epub 2009 Aug 13.
In this work a detailed analysis of the structure, the expression and the organization of his genes belonging to the core of histidine biosynthesis (hisBHAF) in 40 newly determined and 13 available sequences of Burkholderia strains was carried out. Data obtained revealed a strong conservation of the structure and organization of these genes through the entire genus. The phylogenetic analysis showed the monophyletic origin of this gene cluster and indicated that it did not undergo horizontal gene transfer events. The analysis of the intergenic regions, based on the substitution rate, entropy plot and bendability suggested the existence of a putative transcription promoter upstream of hisB, that was supported by the genetic analysis that showed that this cluster was able to complement Escherichia colihisA, hisB, and hisF mutations. Moreover, a preliminary transcriptional analysis and the analysis of microarray data revealed that the expression of the his core was constitutive. These findings are in agreement with the fact that the entire Burkholderiahis operon is heterogeneous, in that it contains "alien" genes apparently not involved in histidine biosynthesis. Besides, they also support the idea that the proteobacterial his operon was piece-wisely assembled, i.e. through accretion of smaller units containing only some of the genes (eventually together with their own promoters) involved in this biosynthetic route. The correlation existing between the structure, organization and regulation of his "core" genes and the function(s) they perform in cellular metabolism is discussed.
在这项工作中，对40个新测定的和13个已有的伯克霍尔德菌属菌株中属于组氨酸生物合成核心基因（hisBHAF）的结构、表达和组织进行了详细分析。所获得的数据表明，这些基因的结构和组织在整个属中具有很强的保守性。系统发育分析表明该基因簇起源于单系，并表明它未经历水平基因转移事件。基于替换率、熵图和弯曲性对基因间区域进行的分析表明，在hisB上游存在一个假定的转录启动子，遗传分析支持了这一点，该分析表明该基因簇能够互补大肠杆菌hisA、hisB和hisF突变。此外，初步的转录分析和微阵列数据分析表明，组氨酸核心基因的表达是组成型的。这些发现与整个伯克霍尔德菌属his操纵子是异质的这一事实相符，因为它包含明显不参与组氨酸生物合成的“外来”基因。此外，它们还支持了变形菌门his操纵子是分段组装的观点，即通过包含参与该生物合成途径的仅一些基因（最终连同它们自己的启动子）的较小单元的积累。讨论了his“核心”基因的结构、组织和调控与其在细胞代谢中所执行功能之间存在的相关性。
