Accumulation of LHCP II apoprotein in wax-rich cells of Euglena in low light or in the presence of streptomycin

Abstract

Cells of Euglena gracilis var. bacillaris or Z strain grown under the usual conditions (“nonwax cells”) and exposed to low-intensity light at the developmental threshold (3–7 ft-c) fail to accumulate LHCP II apoprotein. However, cells grown in a medium rich in hexose without shaking accumulate wax; these wax-rich cells, after subsequent aeration in darkness on an inorganic medium for 6 days, accumulate LHCP II apoprotein on exposure to low-intensity light. Immunoelectron microscopy of these cells using anti-LHCP II antibody and protein A—gold shows LHCP II apoprotein first in the compartmentalized osmiophilic body (COS) and Golgi apparatus followed by the thylakoids of the plastid, as previously seen in nonwax cells at normal light intensities for chloroplast development. With time in the light the aerated wax-rich cells at low light intensity form curly thylakoids which react with the LHCP II antibody; exposure of these cells to high light intensity (500 ft-c) causes the curly thylakoids to assume the more normal straight configuration and these retain the reaction with LHCP II antibody. Aerated dark-grown wax-rich cells exposed to normal light intensities for chloroplast development (150 ft-c) in the presence of 0.1% streptomycin have plastids in which the disappearance of the prolamellar body (PLB) is inhibited; a paracrystalline body is formed in close proximity to the PLB which shows an immunoreaction with LHCP II antibody, but the immunoreaction is absent from the thylakoids. Thus, conditions in the aerated wax-rich cells allow an unusual accumulation of LHCP 11 apoprotein at low light intensities and streptomycin blocks the distribution of this apoprotein to the thylakoids in these cells at normal intensities.