C Department of Plant and Microbial Biology, University of California, 411 Koshland Hall, Berkeley, CA 94720, USA. ABSTRACT The. Key words: Metabolic regulation; molecular transport; transport processes/kinetics; chloroplast biology; protein targeting. In Biochemistry and Molecular Biology of Plants, Buchanan B. Key words: Bioinformatics, metabolomics, networks, nutrient, sulphate, sulphur metabolism, systems biology. Plant biochemistry, molecular biology, and physiology have described the linear routes of ion uptake. Co-factors (for a review see Buchanan et al. Vibe Confessions Rapidshare Search. , 2000). A more holistic approach to understanding the. Biochemistry and Molecular Biology of Plants (2nd Edition) PDF Free Download, Read online, ISBN: By Bob B. Buchanan and Wilhelm Gruissem Download with. Tzfira Tzvi, 'Biochemistry and Molecular Biology of Plants. Buchanan, Wilhelm Gruissem, Russell L. Jones,' The Quarterly Review of Biology 76, no. 3 (Sep., 2001): 359-360. Of all published articles, the following were the most read within the past 12 months.

Abstract Nitrite transport to the chloroplast is not a well documented process in spite of being a central step in the nitrate assimilation pathway. The lack of molecular evidence, as well as the easy diffusion of nitrite through biological membranes, have made this physiological process difficult to understand in plant nutrition. The aim of this review is to illustrate that nitrite transport to the chloroplast is a regulated step, intimately related to the efficiency of nitrate utilization. In Chlamydomonas reinhardtii, the Nar1;1 gene has been shown to have this role in nitrate assimilation. NAR1;1 corresponds to a plastidic membrane transporter protein related to the bacterial formate/nitrite transporters.

At least four Nar1 genes might exist in Chlamydomonas. The existence of orthologous Nar1 genes in plants is discussed.

Plastidic nitrite transport: a regulated process? Compartmentation of different cell processes is known to be a common strategy to enhance the efficiency of the cell function.

Compartmentation has an important regulatory function in metabolism, mostly based on the selective permeability of organelle membranes controlled by specific transporters. This fact results in an increased metabolic flexibility. Chloroplasts carry on key processes in plants such as energy capture and storage, biosynthesis of pigments, purines, pyrimidines, and fatty acids, and the reduction of nitrite and sulphate (). Nitrite, when protonated, is reported to move easily across biological membranes and this fact has hindered the study of its putative specific transporters. In plant and animal cells, anionic channels have been shown to be permeable to both nitrate and nitrite (;;; ). In plants, anion channels contribute to the regulation of a number of physiological processes such as mineral nutrition, turgor‐ and osmoregulation, metal tolerance, and signal transduction etc.

Concerning nitrate assimilation, chloride channels seem to play a role controlling the intracellular nitrate homeostasis. In Arabidopsis thaliana chloride channels have been shown to mediate a sustained anion efflux in hypocotyl cells () and, the disruption of a chloride channel ( AtCLC‐a) gene results in a hypersensitivity to chlorate and a decreased intracellular nitrate accumulation (). Biggies Top Hits.

Chloride channels have also been located in the envelope membrane of chloroplasts and reported to be permeable to nitrate and nitrite (). In addition to the chloride channels which are involved in a number of different physiological processes, specific transporters for nitrate assimilation are also involved. In fact, several gene families corresponding to specific nitrate assimilation transporters (from POT, MFS, and ABC families) have been identified in fungi, yeast, algae, plants, and bacteria, and reported to be involved in the entry of nitrate into the cell (;;; ). In photosynthetic eukaryotic organisms, nitrate assimilation involves two membrane barriers, the plasma and the chloroplast membranes. Thus, once nitrate is reduced to nitrite by the nitrate reductase enzyme in the cytosol, nitrite has to cross the choroplast envelope membranes for its subsequent reduction to ammonium and incorporation into amino acids (; ).