Research Activities- HAYAKAWA Toshihiko -

The study on the signal transduction system of the expression of nitrogen assimilatory genes in rice

Nitrogen (N) and carbon (C) are two most fundamental elements required for plant growth and development. Since N often tends to be shortage, plants have acquired and developed strategic adaptive systems for most effective metabolism and utilization of N to environmental N-conditions during their evolution, for example potent capacities of ammonium assimilation and nitrogen re-mobilization in rice. In rice, expression of transcripts for some genes encoding the key enzyme and proteins on the primary nitrogen metabolism, i.e., NADH-dependent glutamate synthase and ammonium transporters, are regulated by glutamine, which is one of significant N-metabolites. The purpose of our study is to understand the molecular mechanism on the glutamine-mediated signal transduction system and to apply this finding to produce rice having much better capacity for N-metabolism. Firstly, we focus on the initial step of this signaling system. Genes encoding the putative glutamine-signal sensor and transmitter including PII-like protein (OsGlnB) were isolated and their expression profiles in rice were analyzed. The precise physiological roles of these candidates on glutamine-signaling in rice are going to be examined using gene-knock down and/or -knock out rice plants.
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