Reverse genetics approach to characterize a function of NADH-glutamate synthase1 in rice plants.
Rice plants grown in anaerobic paddy soil prefer to use ammonium ion as an inorganic nitrogen source for their growth. The ammonium ions are assimilated by the coupled reaction of glutamine synthetase (GS) and glutamate synthase (GOGAT). In rice, there is a small gene family for GOGAT: there are two NADH-dependent types and one ferredoxin (Fd)-dependent type. Fd-GOGAT is important in the re-assimilation of photorespiratorily generated ammonium ions in chloroplasts. Although cell-type and age-dependent expression of two NADH-GOGAT genes has been well characterized, metabolic function of individual gene product is not fully understood. Reverse genetics approach is a direct way to characterize functions of isoenzymes. We have isolated a knockout rice mutant lacking NADH-dependent glutamate synthase1 (NADH-GOGAT1) and our studies show that this isoenzyme is important for primary ammonium assimilation in roots at the seedling stage. NADH-GOGAT1 is also important in the development of active tiller number, when the mutant was grown in paddy field until the harvest. Expression of NADH-GOGAT2 and Fd-GOGAT in the mutant was identical with that in wild-type, suggesting that these GOGATs are not able to compensate for NADH-GOGAT1 function.
Tamura
Wataru
W
Tohoku University, Aoba-ku, Sendai, Japan.
Hidaka
Yusuke
Y
Tabuchi
Mayumi
M
Kojima
Soichi
S
Hayakawa
Toshihiko
T
Sato
Tadashi
T
Obara
Mitsuhiro
M
Kojima
Mikiko
M
Sakakibara
Hitoshi
H
Yamaya
Tomoyuki
T
D002736:Chloroplasts / Q000235:genetics / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D055786:Gene Knockout Techniques; D050790:Glutamate Synthase (NADH) / Q000235:genetics* / Q000378:metabolism*; D005974:Glutamate-Ammonia Ligase / Q000378:metabolism; D015151:Immunoblotting; D017136:Ion Transport / Q000235:genetics / Q000502:physiology; D009243:NAD / Q000378:metabolism; D012275:Oryza / Q000201:enzymology* / Q000235:genetics* / Q000378:metabolism; D010937:Plant Growth Regulators / Q000032:analysis; D018517:Plant Roots / Q000378:metabolism; D010944:Plants / Q000235:genetics / Q000378:metabolism; D016133:Polymerase Chain Reaction; D000644:Quaternary Ammonium Compounds / Q000378:metabolism*; D018749:RNA, Plant / Q000032:analysis; D036226:Seedlings / Q000378:metabolism; D015398:Signal Transduction
D010937:Plant Growth Regulators; D000644:Quaternary Ammonium Compounds; D018749:RNA, Plant; D009243:NAD; D050790:Glutamate Synthase (NADH); D005974:Glutamate-Ammonia Ligase