TY - JOUR
T1 - Cytosolic glutamine synthetase1;2 is responsible for the primary assimilation of ammonium in rice roots
AU - Funayama, Kazuhiro
AU - Kojima, Soichi
AU - Tabuchi-Kobayashi, Mayumi
AU - Sawa, Yuki
AU - Nakayama, Yosuke
AU - Hayakawa, Toshihiko
AU - Yamaya, Tomoyuki
N1 - Funding Information:
The Japan Society for the Promotion of Science (JSPS) [Grants-in-Aid for Scientific Research (A) (22248005 to T.Y.)]; the Ministry of Education, Culture, Sports, Science and Technology of Japan [Grant-in-Aid for Scientific Research on Innovative Area (22119003 to T.Y.); the Ministry of Agriculture, Forestry and Fisheries of Japan [Genomics for Agricultural Innovation, grant IPG-0008].
PY - 2013/6
Y1 - 2013/6
N2 - Among three genes for cytosolic glutamine synthetase (OsGS1;1, OsGS1;2 and OsGS1;3) in rice (Oryza sativa L.) plants, the OsGS1;2 gene is known to be mainly expressed in surface cells of roots, but its function was not clearly understood. We characterized knock-out mutants caused by the insertion of an endogenous retrotransposon Tos17 into exon 2 of OsGS1;2. Homozygously inserted mutants showed severe reduction in active tiller number and hence panicle number at harvest. Other yield components, such as spikelet number per panicle, 1,000-spikelet weight and proportion of well ripened grains, were nearly identical between the mutants and wild-type plants. When the contents of free amino acids in roots were compared between the mutants and the wild type, there were marked reductions in contents of glutamine, glutamate, asparagine and aspartate, but a remarkable increase in free ammonium ions in the mutants. Concentrations of amino acids and ammonium ions in xylem sap behaved in a similar fashion. Re-introduction of OsGS1;2 cDNA under the control of its own promoter into the knock-out mutants successfully restored yield components to wild-type levels as well as ammonium concentration in xylem sap. The results indicate that GS1;2 is important in the primary assimilation of ammonium ions taken up by rice roots, with GS1;1 in the roots unable to compensate for GS1;2 functions.
AB - Among three genes for cytosolic glutamine synthetase (OsGS1;1, OsGS1;2 and OsGS1;3) in rice (Oryza sativa L.) plants, the OsGS1;2 gene is known to be mainly expressed in surface cells of roots, but its function was not clearly understood. We characterized knock-out mutants caused by the insertion of an endogenous retrotransposon Tos17 into exon 2 of OsGS1;2. Homozygously inserted mutants showed severe reduction in active tiller number and hence panicle number at harvest. Other yield components, such as spikelet number per panicle, 1,000-spikelet weight and proportion of well ripened grains, were nearly identical between the mutants and wild-type plants. When the contents of free amino acids in roots were compared between the mutants and the wild type, there were marked reductions in contents of glutamine, glutamate, asparagine and aspartate, but a remarkable increase in free ammonium ions in the mutants. Concentrations of amino acids and ammonium ions in xylem sap behaved in a similar fashion. Re-introduction of OsGS1;2 cDNA under the control of its own promoter into the knock-out mutants successfully restored yield components to wild-type levels as well as ammonium concentration in xylem sap. The results indicate that GS1;2 is important in the primary assimilation of ammonium ions taken up by rice roots, with GS1;1 in the roots unable to compensate for GS1;2 functions.
KW - Ammonium assimilation
KW - Cytosolic glutamine synthetas
KW - Metabolism
KW - Mutant
KW - Rice
KW - Yield
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U2 - 10.1093/pcp/pct046
DO - 10.1093/pcp/pct046
M3 - Article
C2 - 23509111
AN - SCOPUS:84878838892
VL - 54
SP - 934
EP - 943
JO - Plant and Cell Physiology
JF - Plant and Cell Physiology
SN - 0032-0781
IS - 6
ER -