Nitrogen control of chloroplast differentiation. Annual progress report

Technical Report · Wed Jul 01 04:00:00 EDT 1992

DOI:https://doi.org/10.2172/10158167· OSTI ID:10158167

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, Washington, DC (United States)
• DOE Contract Number: FG09-84ER13188
• OSTI ID: 10158167
• Report Number(s): DOE/ER/13188--8; ON: DE93015558
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
140505
550200
59 BASIC BIOLOGICAL SCIENCES
BIOCHEMISTRY
BIOSYNTHESIS
CHLOROPHYLL-BINDING PROTEINS
CHLOROPLASTS
CYTOCHROMES
GENE REGULATION
MESSENGER-RNA
NITROGEN
NUTRITIONAL DEFICIENCY
ONTOGENESIS
PHOTOCHEMICAL, PHOTOBIOLOGICAL, AND THERMOCHEMICAL CONVERSION
PHOTOSYNTHETIC REACTION CENTERS
PIGMENTS
PROGRESS REPORT
THYLAKOID MEMBRANE PROTEINS