title: Genetic manipulation and quantitative-trait loci mapping for nitrogen recycling in rice.
abstract: Immunocytological studies in this laboratory have suggested that NADH-dependent glutamate synthase (NADH-GOGAT; EC 1.4.1.14) in developing organs of rice (Oryza sativa L. cv. Sasanishiki) is involved in the utilization of glutamine remobilized from senescing organs through the phloem. Because most of the indica cultivars contained less NADH-GOGAT in their sink organs than japonica cultivars, over-expression of NADH-GOGAT gene from japonica rice was investigated using Kasalath, an indica cultivar. Several T0 transgenic Kasalath lines over-producing NADH-GOGAT under the control of a NADH-GOGAT promoter of Sasanishiki, a japonica rice, showed an increase in grain weight (80% as a maximum), indicating that NADH-GOGAT is indeed a key step for nitrogen utilization and grain filling in rice. A genetic approach using 98 backcross-inbred lines (BC(1)F(6)) developed between Nipponbare (a japonica rice) and Kasalath were employed to detect putative quantitative trait loci (QTLs) associated with the contents of cytosolic glutamine synthetase (GS1; EC 6.3.1.2), which is probably involved in the export of nitrogen from senescing organs and those of NADH-GOGAT. Immunoblotting analyses showed transgressive segregations toward lower or greater contents of these enzyme proteins in these BC(1)F(6). Seven chromosomal QTL regions were detected for GS1 protein content and six for NADH-GOGAT. Some of these QTLs were located in QTL regions for various biochemical and agronomic traits affected by nitrogen recycling. The relationships between the genetic variability of complex agronomic traits and traits for these two enzymes are discussed.
authors.affiliation: Graduate School of Agricultural Science, Tohoku University, 1-1 Tsutsumidori-Amamiyamachi, Sendai 981-8555, Japan. tyamaya@biochem.tohoku.ac.jp
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Yamaya
authors.forename: Mitsuhiro
authors.initials: M
authors.lastname: Obara
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Nakajima
authors.forename: Shohei
authors.initials: S
authors.lastname: Sasaki
authors.forename: Toshihiko
authors.initials: T
authors.lastname: Hayakawa
authors.forename: Tadashi
authors.initials: T
authors.lastname: Sato
mesh_terms: D000594:Amino Acid Oxidoreductases / Q000235:genetics / Q000378:metabolism; D002874:Chromosome Mapping; D002523:Edible Grain / Q000201:enzymology / Q000235:genetics / Q000254:growth & development; D004798:Enzymes / Q000235:genetics* / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D050790:Glutamate Synthase (NADH); D005974:Glutamate-Ammonia Ligase / Q000235:genetics / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism*; D012275:Oryza / Q000201:enzymology / Q000235:genetics* / Q000254:growth & development; D030821:Plants, Genetically Modified; D019655:Quantitative Trait, Heritable
chemical_list: D004798:Enzymes; D000594:Amino Acid Oxidoreductases; D050790:Glutamate Synthase (NADH); C042233:glutamate synthase (ferredoxin); D005974:Glutamate-Ammonia Ligase; D009584:Nitrogen