Abstract
In rice, expression of NADH-GOGAT and OsAMT1;1-3 is regulated by glutamine (gln). To clarify the molecular mechanism of the gln-signaling system on nitrogen assimilation in rice, we isolated rice genes encoding ACT-domain repeat proteins (OsACR2-7), whose four-repeating domains were similar to those of bacterial gln-sensor GlnD. RT-PCR analysis showed in rice, transcripts of OsACR3, OsACR5 and OsACR6 were abundant in sheaths and blades of leaves and that of OsACR7 in spikelets, whereas OsACR2 and OsACR4 near-constitutively expressed in all organs tested. By the way, the RNAi vector containing the fragment of 3'-untranslated region of OsACR3 cDNA as trigger expressed under regulation by ubiquitin promoter was introduced into rice callus. In regenerated transformants, the expression of OsACR3 was markedly suppressed. The heights of the OsACR3-knock down rice in reproductive stages were lower than those of wild-types. Analysis of the expression of nitrogen-assimilatory genes in OsACR3-knock down rice is underway.
