The role of lateral gene transfer in the evolution of isoprenoid biosynthesis pathways

Lateral gene transfer (LGT) is a major force in microbial genome evolution. Here, we present an overview of lateral transfers affecting genes involved in isopentenyl diphosphate (IPP) synthesis. Two alternative metabolic path ways can synthesize this universal precursor of isoprenoids, the 1-deoxy-d- xylulose 5-phosphate (DOXP) pathway and the mevalonate (MVA) pathway. We ha ve surveyed recent genomic data and the biochemical literature to determine the distribution of the genes composing these pathways within the bacteria l domain. The scattered distribution observed is incompatible with a simple scheme of vertical transmission. LGT (among and between bacteria, archaea and eukaryotes) more parsimoniously explains many features of this pattern. This alternative scenario is supported by phylogenetic analyses, which una mbiguously confirm several cases of lateral transfer. Available biochemical data allow the formulation of hypotheses about selective pressures favouri ng transfer. The phylogenetic diversity of the organisms involved and the r ange of possible causes and effects of these transfer events make the IPP b iosynthetic pathways an ideal system for studying the evolutionary role of LGT.