Department of Metabolic Biology, John Innes Centre, Norwich NR4 7UH, United Kingdom.
Proc Natl Acad Sci U S A. 2011 Sep 20;108(38):16116-21. doi: 10.1073/pnas.1109273108. Epub 2011 Aug 29.
In bacteria, genes with related functions often are grouped together in operons and are cotranscribed as a single polycistronic mRNA. In eukaryotes, functionally related genes generally are scattered across the genome. Notable exceptions include gene clusters for catabolic pathways in yeast, synthesis of secondary metabolites in filamentous fungi, and the major histocompatibility complex in animals. Until quite recently it was thought that gene clusters in plants were restricted to tandem duplicates (for example, arrays of leucine-rich repeat disease-resistance genes). However, operon-like clusters of coregulated nonhomologous genes are an emerging theme in plant biology, where they may be involved in the synthesis of certain defense compounds. These clusters are unlikely to have arisen by horizontal gene transfer, and the mechanisms behind their formation are poorly understood. Previously in thale cress (Arabidopsis thaliana) we identified an operon-like gene cluster that is required for the synthesis and modification of the triterpene thalianol. Here we characterize a second operon-like triterpene cluster (the marneral cluster) from A. thaliana, compare the features of these two clusters, and investigate the evolutionary events that have led to cluster formation. We conclude that common mechanisms are likely to underlie the assembly and control of operon-like gene clusters in plants.
在细菌中，具有相关功能的基因通常会聚集在一起形成操纵子，并作为单个多顺反子 mRNA 被共转录。在真核生物中，功能相关的基因通常分散在基因组中。值得注意的例外包括酵母中分解代谢途径的基因簇、丝状真菌中次生代谢物的合成以及动物中的主要组织相容性复合体。直到最近，人们还认为植物中的基因簇仅限于串联重复（例如富含亮氨酸的重复疾病抗性基因的阵列）。然而，植物生物学中出现了操纵子样的核心调控非同源基因簇，它们可能参与某些防御化合物的合成。这些簇不太可能是通过水平基因转移产生的，其形成的机制也知之甚少。先前在拟南芥中，我们鉴定了一个操纵子样基因簇，该基因簇是合成和修饰三萜类化合物 thalianol 所必需的。在这里，我们从拟南芥中鉴定了第二个操纵子样三萜类基因簇（marneral 基因簇），比较了这两个基因簇的特征，并研究了导致基因簇形成的进化事件。我们得出结论，共同的机制可能是植物中操纵子样基因簇组装和调控的基础。
