Nitrogen control of chloroplast differentiation

Technical Report · Wed Jul 01 00:00:00 EDT 1992

DOI:https://doi.org/10.2172/6443913· OSTI ID:6443913

Schmidt, G W

This project is directed toward understanding how the availability of nitrogen affects the accumulation of chloroplast pigments and proteins functioning in energy transduction and carbon metabolism. Molecular analyses performed with Chlamydomonas reinhardtii grown in a continuous culture system such that ammonium concentration is maintained at a low steady-state concentration so as to limit cell division. As compared to chloroplasts from cells of non-limiting nitrogen provisions, chloroplasts of N-limited cells are profoundly chlorophyll-deficient but still assimilate carbon for deposition of as starch and as storage lipids. Chlorophyll deficiency arises by limiting accumulation of appropriate nuclear-encoded mRNAs of and by depressed rates of translation of chloroplast mRNAs for apoproteins of reaction centers. Chloroplast translational effects can be partially ascribed to diminished rates of chlorophyll biosynthesis in N-limited cells, but pigment levels are not determinants for expression of the nuclear light-harvesting protein genes. Consequently, other signals that are responsive to nitrogen availability mediate transcriptional or post-transcriptional processes for accumulation of the mRNAs for LHC apoproteins and other mRNAs whose abundance is dependent upon high nitrogen levels. Conversely, limited nitrogen availability promotes accumulation of other proteins involved in carbon metabolism and oxidative electron transport in chloroplasts. Hence, thylakoids of N-limited cells exhibit enhanced chlororespiratory activities wherein oxygen serves as the electron acceptor in a pathway that involves plastoquinone and other electron carrier proteins that remain to be thoroughly characterized. Ongoing and future studies are also outlined.

• Research Organization: Georgia Univ., Athens, GA (United States). Research Foundation
• Sponsoring Organization: USDOE; USDOE, Washington, DC (United States)
• DOE Contract Number: FG09-84ER13188
• OSTI ID: 6443913
• Report Number(s): DOE/ER/13188-8; ON: DE93015558
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
59 BASIC BIOLOGICAL SCIENCES
CHLOROPHYLL-BINDING PROTEINS
BIOSYNTHESIS
CHLOROPLASTS
ONTOGENESIS
CYTOCHROMES
GENE REGULATION
MESSENGER-RNA
NITROGEN
NUTRITIONAL DEFICIENCY
PHOTOSYNTHETIC REACTION CENTERS
PIGMENTS
PROGRESS REPORT
THYLAKOID MEMBRANE PROTEINS
CELL CONSTITUENTS
DOCUMENT TYPES
ELEMENTS
MEMBRANE PROTEINS
NONMETALS
NUCLEIC ACIDS
ORGANIC COMPOUNDS
PROTEINS
RNA
SYNTHESIS
140505* - Solar Energy Conversion- Photochemical
Photobiological
& Thermochemical Conversion- (1980-)
550200 - Biochemistry