Appearance of Chlorophyll-Protein Complexes in Greening Barley Seedlings

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The sequential appearance of chlorophyll-protein complexes (CP) in greening barley leaves was studied by an improved method of SDS-polyacrylamide gel electrophoresis (PAGE). Solubilized thylakoid membranes were purified using a sucrose step gradient and CPs were separated by PAGE with low concentrations of SDS in solubilizing and reservoir buffers. At 10min after the onset of illumination, a chlorophyll-protein complex (CPX) was detected. It was a labile CP, its chlorophyll (Chl) being easily released from the apoprotein during electrophoresis. The P700-chlorophyll a-protein complex (CP1) appeared after 45-60 min of illumination together with P700 activity. Light-harvesting chlorophyll a/b-protein complex (LHCP) began to accumulate at 2.5 h with the beginning of Chl b synthesis. In some cases a small amount of CPa could be detected after 6 h of greening. The time-difference spectrum between homogenates of leaves illuminated for 30 and 60min had an absorbance maximum at 677nm, showing that a red shift indicative of CP1 formation began soon after completion of the Shibata shift. The time-difference spectrum between 3.5-h and 4.0-h illuminated leaves resembled the absolute spectrum of fully greened leaves, indicating that at this stage, spectral components were being synthesized at the same ratio at which they exist in fully greened tissues. Both absolute and time-difference spectral data supported the SDS-PAGE results.
日本植物生理学会の論文