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

Abstract

Exposure of dark grown resting Euglena to light induces the transformation of the proplastid into a photosynthetically competent chloroplast. The synthesis of chloroplast proteins occurs in resting cells without a net increase in total cellular protein (3). 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. The decreased level of mitochondrial proteins is due to a light dependent decrease in their rate of synthesis rather than to an increase in their rate of degradation ( 14). As the rate of synthesis of mitochondrial proteins decreases, their levels decline through turnover.

Extremely large and slowly processed precursors to the Euglena light-harvesting chlorophyll a/b binding proteins of photosystem II

“…It was proposed that the pLHCPII was a 28-kDa cell-free translation product encoded by an mRNA whose concentration in the polysomal fraction increased when LHCPII synthesis was preferentially induced by transferring intermittently illuminated cells to continuous illumination (39). Present results show that the pLHCPIIs are indeed large, up to twice as large as previously reported (30,38), and that they are produced and slowly processed to LHCPIIs in vivo.…”

“…Samples were preadsorbed with 30 ,lI of protein A-Sepharose (Sigma) for 20 min at 4°C and then centrifuged for 2 min at 10,000 x g. The pellet was discarded, and 2.0 ,u of polyclonal monospecific antibody against Euglena LHCPII (24) was added to the supernatant. After incubation for 30 min at 4°C, 30 ,ul ofprotein A-Sepharose was added, and the mixture was incubated for 30 min at 4°C with shaking. The antigenantibody-protein A-Sepharose complex was recovered by centrifugation for 2 min at 10,000 x g. The pellet was washed four times with RIPA buffer containing 1 M NaCl and twice with RIPA buffer.…”

Photo and Nutritional Regulation of the Light-Harvesting Chlorophyll a/b-Binding Protein of Photosystem II mRNA Levels in Euglena

“…The increase in the rate of pLHCPII synthesis (19) is probably the result of the increase in LHCPII mRNA levels. In contrast with the translational control of the shift up induction of mitochondrial enzymes (2,20), the shift up induction of chloroplast proteins such as LHCPII appears to be regulated at the transcriptional level.…”

“…The bleached mutants W3BUL and W10BSmL derived from this strain lack detectable Pchl(ide) and have lost most if not all of their chloroplast genome (16,17,25). Conditions for cell growth, preparation of resting cells, and light-induced chloroplast development have been described (7,14,20).…”

“…Light, ethanol, and malate induce fumarase in carbon-starved cells (7,20) while having no effect on fumarase levels in growing cells (9). Because light allows CO2 to be used as the sole source of carbon and energy for growth, fumarase induction can be viewed as a response of starving cells to the provision of a utilizable carbon source, a nutritional shift up.…”