ABSTRACT
In this work we studied the influence of exogenous ammonium on the total protein and chlorophyll contents, on the number of ribosomes and on the expression of ribosomal genes encoding the small subunit 18S rRNA and rpS6 protein in unicellular green alga Chlamydomonas reinhardtii and in callus tissue of Glycine max. Comparative analysis of two sets of data showed that although the lack of ammonium resulted in reduction of the number of ribosomes in alga and plant cells, this effect was not caused by decreasing of the expression level of the ribosomal genes. Possible mechanisms of the ammonium regulatory role in the ribosome biogenesis are discussed.
Subject(s)
Chlamydomonas reinhardtii/drug effects , Glycine max/drug effects , Nitrates/pharmacology , Ribosomes/drug effects , Algal Proteins/genetics , Algal Proteins/metabolism , Chlamydomonas reinhardtii/genetics , Chlamydomonas reinhardtii/metabolism , Chlorophyll/biosynthesis , Gene Expression , Plant Proteins/genetics , Plant Proteins/metabolism , RNA, Ribosomal, 18S/genetics , RNA, Ribosomal, 18S/metabolism , Ribosomal Protein S6/genetics , Ribosomal Protein S6/metabolism , Ribosomes/genetics , Ribosomes/metabolism , Glycine max/genetics , Glycine max/metabolism , Species SpecificityABSTRACT
In the present review the role of ammonium component not connected with the synthesis of nitrogen-containing substances in plant cells is discussed. In particular, it is devoted to the influence of NH4+ ions on the morphological changes of surface root cells, heterotrophic CO2 fixation by cells, dark and light-dependent reduction of nitrate in plant cells, formation and functioning of cytoplasmic ribosomes in plant cells and function of photosynthesizing organelle membrane systems. Our experimental data together with the results of the other researchers allow us to look at ammonium participation in the life of plant cells more widely and not to consider NH4+ ions only as a substrate for ketoacids amination processes in plant cells.
Subject(s)
Plant Roots/cytology , Plant Roots/metabolism , Quaternary Ammonium Compounds/metabolism , Carbon Dioxide/metabolism , Intracellular Membranes/metabolism , Nitrates/metabolism , Organelles/metabolism , Photosynthesis , Plant Proteins/biosynthesis , Ribosomes/metabolismABSTRACT
We studied the influence of exogenic ammonium on the functional activity and ultrastructural organization of cells of the mixotrophic soybean callus (Glycine max L.). Ammonium available in the nutrient medium increased the chlorophyll content, accelerating the rate of photosynthetic O2 evolution per unit of biomass. The presence of ammonium in the medium promoted formation of the protein-synthesizing system, which manifested itself as increased numbers of ribosomes, and thylakoids of chloroplasts, and higher electron density of the stroma in mitochondria and cytoplasm of mixotrophic cells. It has been concluded that the use of ammonium may lead to activation of protein synthesis, thus rising photosynthetic activity and favouring formation and development of membrane structures in chloroplasts.
Subject(s)
Chloroplasts/drug effects , Glycine max/drug effects , Nitrates/pharmacology , Photosynthesis/drug effects , Quaternary Ammonium Compounds/pharmacology , Cells, Cultured , Chlorophyll/analysis , Chlorophyll/biosynthesis , Chloroplasts/metabolism , Chloroplasts/ultrastructure , Culture Media , Microscopy, Electron , Oxygen/metabolism , Ribosomes/metabolism , Glycine max/metabolism , Glycine max/ultrastructure , Thylakoids/metabolism , Time FactorsABSTRACT
We studied the role of light during exogenous assimilation of nitrate (as the only source of nitrogen) by the callus cells of soybean (Glycine max). The nitrate absorbed and assimilated by the photosynthetic (mixotrophic) and non-photosynthetic cells (heterotrophic and chlorophyll-containing cells cultivated in the light in the same medium with diuron) was quantified. The assimilated nitrate was quantified at the final stage of the growth cycle as the difference between the amount of nitrogen absorbed from the medium and the amount of endogenous nitrate in the cells. Comparison of the assimilated nitrate quantities per accumulated dry biomass between the photosynthetic and non-photosynthetic cells demonstrated that nearly 30% of nitrate is assimilated with the help of photosynthesis in a mixotrophic culture when nitrate is the only source of nitrogen.
