Photocontrol of Chloroplast and Mitochondrial Polypeptide Levels in Euglena

Abstract

Two dimensional polyacrylme gel electrophoresis resolved protein from intact chkroplasts of wild type Eugkxagrailis Klebs var. bacillaris Cori into 185 polypeptides of which 55 were lli on the whole cell polypeptide map. Of these chloroplast polypeptides, the relative amounts of 49 inased, the relative amounts of two decreased, and the relative amounts of four polypeptides were unaltered by exposure of dark grown resting cells to Light for 72 hours. Proteins from intact purified mitochondria obtined from a bleached mutant (W,.BSmL) lacking plastids were resolved into 193 polypeptides of which 44 were lalized on the whole cell polypeptide map from wild type cells. Of these mitochondrial polypeptides, the relative amount of one increased, the relative amounts of 12 were unaltered, and the relative amounts of 31 decreased after exposure of the dark grown rest cells to light. Since it is known that the development of the choroplast in Eagkxa occurs without a net increase in total cellular protein and without a chae in the size of the cellular amino acid pools, the degradation of mitochondrial polypeptides represents a major source of amino acids for the synthesis of chloroplast polypeptides.Light acting through a blue absorbing nonchloroplast photoreceptor, a red absorbing nonchloroplast photoreceptor, and a blue-red absorbing chloroplast photoreceptor which may be Pchl(ide) controls the polypeptide con;position of Euglena (24). mitochondrial Cyt (23). Based on electron microscopic (13,22,23) and autoradiographic studies (23), mitochondrial structure and proteins appear to be degraded during chloroplast development.In nondividing carbon starved resting cells, the carbon skeletons and energy required for chloroplast development are obtained through the degradation of preexisting molecules. Light promotes the degradation of the storage carbohydrate paramylum (25) and the degradation of RNA (3). Chloroplast proteins are synthesized in the absence of a net increase in total cellular proteins (23,24). Since the size of the amino acid pools remains constant during chloroplast development (23), the amino acids used for the synthesis of chloroplast proteins must be derived through the degradation of preexisting proteins. In photosynthetic cells, the chloroplast can provide most of the ATP, fatty acids, storage carbohydrates, and carbon skeletons required for growth. Enzymes required for the synthesis of these compounds during organotrophic growth are at least partially gratuitous during phototrophic growth and they are likely to be degraded to provide the amino acids for the synthesis of chloroplast proteins.Although it is clear that light selectively alters the polypeptide composition of the cell, the extent to which these alterations are localized in specific cellular compartments remains unclear. Studies of changes in the specific activity of individual enzymes are time consuming and they provide information regarding only a single enzyme whose regulation may not be charcteristic of the regulation of the majority...

Translational Regulation of the Synthesis of Euglena Fumarase by Light and Ethanol

“…Amino acids required for the synthesis of chloroplast proteins must be provided through the degradation of preexisting proteins. Light exposure decreased the amounts of 70% of the mitochondrial proteins which were localized on silver stained two-dimensional gels (13). Mitochondrial proteins appear to represent a major source of amino acids for the synthesis of chloroplast proteins.…”

Photo and Nutritional Regulation of Euglena Organelle Development

“…The relative amounts of 49 (90%), of the chloroplast proteins localized to the whole cell map increased, the relative amounts of two decreased and the relative amounts of four were unaltered by light exposure ( Fig. 9.2; Monroy et al 1986;Monroy and Schwartzbach 1983). Analysis by 2-D gels of proteins extracted from cells pulse labeled with 35 S-sulfate showed that the relative rate of synthesis of 61 polypeptides increased with the relative rate of synthesis of 18 increasing by more than threefold during the first half hour of light exposure (Monroy et al 1987).…”

“…9.2; Monroy and Schwartzbach 1983). Proteins extracted from purified chloroplasts were resolved into 185 polypeptides and 55 were localized on the whole cell 2-D gels (Monroy et al 1986). The relative amounts of 49 (90%), of the chloroplast proteins localized to the whole cell map increased, the relative amounts of two decreased and the relative amounts of four were unaltered by light exposure ( Fig.…”

Diurnal Rhythmicity in the Pattern of mRNAs in the Leaves of Sinapis alba

“…This extract was used for two gels. Moreover, differences were considered only when detected in all of the 16 possible comparisons between the four gels of sample A and the four gels of sample B (14,19). According to the statistical test of Mann-Whitney, the probability that two samples, one with the four smallest values and the other with the four greatest values, belong to the same population is 0.02.…”