Abstract
NEP is one of two heterologous transcription systems in plastids and belongs to T7 phage-type RNA polymerase. Arabidopsis has two NEP genes encoding RPOTmp (RPOT;2) and RPOTp (RPOT;3) on the nuclear genome. It has been suggested that RPOTmp probably localizes in both chloroplast and mitochondria. It is physiologically involved in root development and possibly activates a rrn16 promoter. However, the molecular detail of its functional significance is still unclear. We focus in direct and indirect function of RPOTmp in the expression of translational machineries including tRNAs and ribosomal proteins. We characterized therpoTmp mutant by (1) northern and QPCR analyses of nuclear- and plastid-encoded genes for plasidic translation system, (2) polysome analysis, (3) stress response to high light and several reagent affecting chloroplast function, and (4) quantification of plastid DNA content. From these results, we will discuss the involvement of RPOTmp in the expression of plastidic translation system.
