Abstract
Non-symbiotic hemoglobins (ns-Hb) are found in all plants although their physiological function remains to be determined. Two class-1 ns-Hb genes, ORYsa GLB1a and ORYsa GLB1b in cultured rice cells were strongly induced by nitrate, nitrite and nitric oxide (NO) donors. The rapid and transient accumulation of ORYsa GLB1a and ORYsa GLB1b transcripts in response to nitrate, nitrite and NO donors was similar to that of nia1, which encodes nitrate reductase. Although the kinetics of induction by these molecules are similar for the two ns-Hb genes, an inhibitor study demonstrated that de novo synthesis of the protein in cytoplasm is essential for inducing ORYsa GLB1b. By contrast, ORYsa GLB1a, like nia1, can be induced in the primary response to these signals without de novo protein synthesis. These results suggested that the pathway to lead the expression in response to nitrate, nitrite and NO is partly different between two class-1 ns-Hb genes.
