Location of chlorophyll a and b synthesis in etiochloroplast membrane

The process of Chl a formation is rather well described for greening etiolated plants, where it is mediated by PChl-NADPH-oxidoreductase and is located in PLB and PT. The mechanisms and location of CHl a formation in the chloroplasts of green plants is yet unknown, but it takes place through the whole leaf life. There are not many data on the mechanism of Chl b biosynthesis; it is formed from Chl a and starts to accumulate in about 6 h after the beginning of irradiation of etiolated plants. The lack of evidence for the mechanism of Chl formation in green leaves is mainly due to the lack of appropriate methods for its study. Some years ago we detected a short-wavelength fluorescence in green leaves and isolated chloroplasts with emission and excitation spectra of monomeric Chl a, Chl b and PChl. This fluorescence increased with activating the Chl synthesis (at the early stages of leaf development, or after suppression of the formation of some CPs by the herbicide norflurazon). After segregation of chloroplast membranes, the monomeric pigments were mostly found in the supernatant 144 000 x g, but they could be precipitated by protein complexing compounds, such as (NH4)2SO4 or Ca-phosphate gel, which indicated the pigments' attachment to a protein. In this study we try to localize the monomeric pigments in etiochloroplast membrane, which is formed at the intermediate stage of chloroplast development. At this stage PT and PLB of etioplasts transform into thylakoids of mature chloroplasts. Electron micrographs of etiochloroplast PM show that it is composed of an electron transparent base and electron dense inclusions - FLS. In the course of chloroplast development the segments of FLS transform into ring-like structures-prothylakoids - and then into grana. The FLS, separated from the electron transparent base with trypsin, consist of networks of polyribosomes and some membrane components, including CPs. They also incorporate most of etiochloroplast pigments. Here we compare morphology and spectra of PM and FLS in order to localize different CPs and pigments there.