Enhancement of NH+4 Uptake by NO−3 in Relation to Expression of Nitrate-Induced Genes in Rice (Oryza sativa) Roots

This study aimed to survey the expression of genes involved in rice N uptake and assimilatory network and to understand the potential molecular mechanisms responsible for the NO−3 -enhanced NH+4 uptake. By using quantitative real-time polymerase chain reaction (PCR), the genes related to N nutrition, including ammonium transporters (AMTs) and ammonium assimilatory enzymes (GS and GOGAT), were transcriptionally analyzed in rice plants grown in the absence and presence of NO−3 in the NH+4 -containing medium. The results showed that NH+4 uptake by rice was enhanced by the NO−3 supply to the medium. At the same time and in parallel, the amount of transcripts of seven genes (OsAMT1;1, OsAMT1;2, OsAMT4;1, OsGLN2, OsGLN2, OsGLT1, and OsGLT2) was increased in rice roots, but the expression of two genes (OsGLN1;1 and OsGLN1;2) was decreased and that of OsAMTl;3 remained without change. Up- or down-regulation of these genes involved in NH+4 uptake and assimilation correlated with the increase in NH+4 uptake in the presence of NO−3 in rice roots.