Abstract
Monotropastrum humile belongs to Monotropeae, Monotropoideae in Ericaceae and is an achlorophyllous plant due to loss of chlorophyll. In addition, because M.humile has no photosynthetic capacity and is an obligate myco-heterotrophic plant, the life of this plant is completely dependent on the photosynthates supplied by symbiont mycorrhizal fungi. Since proplastid does not seem to differentiate to chloroplast in M.humile, we tried to figure out the molecular mechanism of shifting to achlorophylly in the M.humile by focusing on plastid differentiation. The analysis using DAPI staining and transmission electron microscope showed that M.humile has undifferentiated proplastid-like organelle. Western blot analysis demonstrated that M.humile does not have any RuBisCO subunit proteins (rbcS,rbcL). The analysis of genome DNA and RT-PCR analysis demonstrated that rbcS is transcribed, but rbcL is not. Because rbcL is transcribed by bacterial RNA polymerase (PEP) concerned with transcriptional control for differentiation of plastid to chloroplast, we suggest that proplastid in M.humile does not differentiate to chloroplast due to lacking the function of PEP.
