Abstract
Plastids are semiautonomous higher plant organelles possessing own genome and exhibiting their own gene expression system. Genes encoded in plastid genome are transcribed by PEP and/or NEP. PEP (plastid-encoded plastid RNA polymerase) is composed of the core enzyme including catalytic subunits and σ factors which regulate the transcriptional initiation. Furthermore, it is considered that transcriptional regulator proteins and additional PEP subunits which modulate enzymatic activity also exist in plastids.
We have been already prepared the PEP fraction, which excludes σ factors-related activities, from wheat plastids. Proteins contained within this fraction were analyzed by mass spectrometry (LC-MS/MS). As expected, all PEP core subunits (α, β, β', β") were included in this fraction, however any σ factor proteins were not detected. This fraction also contains several proteins related to the plastid gene expression and protein maturation, e.g., transcription-related proteins, ribosomal proteins and molecular chaperones. This study was partly supported by METI/NEDO.
