Sugar sensing and α-amylase gene repression in rice embryos

被引:93
作者
Umemura, T
Perata, P
Futsuhara, Y
Yamaguchi, J [1 ]
机构
[1] Nagoya Univ, BioSci Ctr, Nagoya, Aichi 46401, Japan
[2] Meijo Univ, Tenpaku, Nagoya, Aichi 468, Japan
[3] Univ Pisa, Dip Biol Piante Agr, Sez Fisiol Vegetale, I-56124 Pisa, Italy
基金
日本学术振兴会;
关键词
alpha-amylase; catabolite repression; hexokinase; Oryza; sugar sensing;
D O I
10.1007/s004250050275
中图分类号
Q94 [植物学];
学科分类号
071001 ;
摘要
We used a transient expression system to study the mechanism by which carbohydrates repress a lice (Oryza sativa L.) alpha-amylase (EC 3.2.1.1) gene. Exogenously fed metabolizable carbohydrates are able to elicit repression of the alpha-amylase gene RAmy3D in the rice embryo, and our results indicate that repression is also triggered efficiently by endogenous carbohydrates. Glucose analogs that are taken up by plant cells but not phosphorylated by hexokinase are unable to repress the alpha-amylase gene studied, while 2-deoxyglucose, which is phosphorylable but not further metabolized, downregulates RAmy3D promoter activity, indicating a role for hexokinase in the sugar-sensing mechanism triggering repression of the RAmy3D gene. We tested two different hexokinase inhibitors, mannoheptulose and glucosamine, but only the latter was able to relieve RAmy3D promoter activity from repression by endogenous carbohydrates. This correlates with the higher ability of glucosamine to inhibit the activity of rice hexokinases in vitro. The glucosamine-mediated relief of RAmy3D promoter activity from repression by endogenous carbohydrates does not correlate with a reduced rate of carbohydrate utilization.
引用
收藏
页码:420 / 428
页数:9
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