Biogenesis of photosynthetic apparatus in etiolated leaves during greening
Year: 1986
Type: article
Abstract: Using incorporation of exogenous substrates in chlorophyll biosynthesis chain it was found that in etiolated leaves there is a machinery capable of chlorophyllide a to chlorophyll a and chlorophyllide b to chlorophyll b transformations as well as inverse transformation of chlorophyll b into chlorophyll a. Immunochemical methods were employed to reveal protein precursors of pigment-protein complex I, pigment-protein complex II and light-harvesting complex in etioplasts. The investigation of the fluorescence excitation spectra has shown that just after illumination of etiolated leaves Photosystem I appears as a system of respective chlorophyll forms with an efficient energy sink to the longwave minor form emitting at 720 nm. The study of delayed luminescence indicates that Photosystem II arises as early as during the Shibata shift. While being incorporated into Photosystems, chlorophyll molecules undergo at least two translocations from the sites of their synthesis. Chlorophyll 672 is likely to be a special pigment pool utilized for the construction of the photosynthetic apparatus. In the course of the Shibata shift, the translocation rate of chlorophyll molecules to the new surrounding varies within ontogenesis of seedlings and also under the influence of chloramphenicol and cycloheximide. Meanwhile, there is no rapid photoinduced synthesis of new proteins in plastids. Photoinduced increase of the chlorophyll synthesis rate in greening leaves is accompanied by accumulation of magnesium protoporphyrin IX monomethyl ester, and the constant rate of greening coincides with a decrease of the intermediate content. The analysis of the pigment synthesis rates under continuous and intermittent illumination suggests existence of two types of the centers of chlorophyll biosynthesis which differ in the light regulation of 6-aminolevulinic acid synthesis and, probably, in their abilities to produce chlorophylls a and b.
Language: English
Subfield: Molecular Biology
Domain: Life Sciences
Open Access status: hybrid
OpenAlex ID: W4402172376