Expression analysis of the glutamine synthetase and glutamate synthase gene families in young rice (Oryza sativa) seedlings

Abstract: Glutamine synthetase (GS) and glutamate synthase (GOGAT) serve for primary assimilation of N in higher plants. When NH4 + is the major inorganic N source, rice plants must assimilate NH4 + quickly in roots through the GS/GOGAT cycle to ameliorate the toxic effect of excess NH4 +. The sequence of the rice genome is almost complete, facilitating the identification of the GS and GOGAT gene families in this species. Thus, we investigated the different members of GS and GOGAT genes, and analyzed the pattern of expression of each gene in young rice seedlings by quantitative real-time PCR, revealing a distinct expression pattern for these genes. OsGln1;1 and OsGln1;2 mainly functions in roots, and OsGln2 and OsGlu1 are preferentially expressed in leaves. However, transcriptions of OsGln1;1, OsGln1;2, OsGln2 and OsGlu1 in leaves are all increased by increased N level while those in roots not influenced or even decreased. OsGlt1 and OsGlt2 are expressed primarily in roots when N is limiting, but in leaves when non-limiting. Transcription of OsGlt1 is decreased, but OsGlt2 is increased by increased N level in roots and leaves. When rice roots are exposed to NO3 − and NH4 + for 2h after N-starvation, transcriptions of OsGln1;1, OsGlt1, OsGlt2 and OsGlu1 are all repressed by NO3 − and NH4 +. OsGln1;2 expression shows significant up-regulation by NH4 + and down-regulation by NO3 − while OsGln2 down-regulation by NH4 + and up-regulation by NO3 −. [Copyright &y& Elsevier]