[Structure and evolution of the prolamellar body in the protoplasts of Euglena gracilis]

Evolution of PS IIα and PS IIβ centers during the greening of Euglena gracilis Z: Correlations with changes in lipid content

The building up of the two types of reaction centers, PS IIα and PS IIβ, was investigated during the greening of Euglena gracilis Z cells in resting medium. The maximal values in the proportion of PS IIα centers (55%) and in the oxygen evolved per chlorophyll were reached at the outbreak of greening, when accumulation of galactolipids (MGDG and DGDG) rich in unsaturated fatty acids occurred, and when anionic lipids (SQDG and PG) emerged. As the greening progressed, the chlorophyll accumulation corresponded to a secondary enrichment in PS IIβ centers, which built up more rapidly than PS IIα centers; correlatively, a general saturation of the fatty acids constitutive of all lipid classes took place.

The effect of glucose on the biochemical and ultrastructural characteristics of developing Euglena chloroplasts

Chloroplast development is inhibited in Euglena gracilis strain Z, when greened in a medium containing glucose. This inhibition is reflected not only in the pattern of chlorophyll accumulation but also in the chloroplast ultrastructure and activities of the 2 light reactions of photosynthesis. Chloroplasts of cells greening in the presence of glucose are delayed in developing certain structures. Photosystem I activity develops at about the same rate as that of the controls during the first 48 h of greening, after which it develops at a slower rate. The rate of development of photosystem II activity in cells greening in a glucose medium lags considerably behing that of the controls until the later hours of greening. There are similarities between glucose inhibition and chloramphenicol inhibition of chloroplast development. Glucose may inhibit a step in chloroplast development ultimately controlled by the chloroplast genome.