Expression of asparagine synthetase in rice (Oryza sativa) roots in response to nitrogen.
The expression of asparagine synthetase (AS; EC 6.3.5.4) in response to externally supplied nitrogen was investigated with respect to enzyme activity and protein levels as detected immunologically in rice (Oryza sativa) seedlings. The asparagine content was very low in leaves and roots of nitrogen-starved rice plants but increased significantly after the supply of 1 mM NH4+ to the nutrient solution. While neither AS activity nor AS protein could be detected in leaves and roots prior to the supply of nitrogen, levels became detectable in roots but not in leaves within 12 h of the supply of 1 mM NH4+ or 10 mM glutamine. Other nitrogen compounds, such as nitrate, glutamate, aspartate and asparagine had no effect. Methionine sulfoximine completely inhibited the NH4+-induced accumulation of AS protein but did not affect the glutamine-induced accumulation of the enzyme. The results suggested that glutamine or glutamine-derived metabolites regulate AS expression in rice roots.
Kawachi
Tahei
T
Department of Environmental and Biological Science, Faculty of Agriculture, Kobe University, Kobe 657-8501, Japan Department of Biofunctional Chemistry, Faculty of Agriculture, Kobe University, Kobe 657-8501, Japan Present address: Department of Applied Biological Chemistry, Faculty of Agriculture, Niigata University, Niigata 950-2181, Japan.
Sueyoshi
Kuni
K
Nakajima
Ayumi
A
Yamagata
Hiroshi
H
Sugimoto
Toshio
T
Oji
Yoshikiyo
Y