中文摘要：

谷氨酰胺合成酶（GS）家族是甜菜等高等植物体内氨态氮同化酶，也是氮利用与循环的核心构件。为揭示在氮素诱导下放线菌素D（AMD）和放线菌酮（CHM）对甜菜GS基因调控表达的影响，采用半定量RT-PCR技术，对甜菜的胞液型谷氨酰胺合成酶基因（GS1）和质体型谷氨酰胺合成酶基因（GS2）进行mRNA的表达检测，同时进行GS活性的测定。结果表明，甜菜幼苗经过低浓度AMD处理2-6h，GS活性略有增加，9h后，高和低浓度AMD处理下的GS活性都下降，且随着浓度的增加下降幅度加大，同时GS1mRNA和GS2mRNA的相对量随浓度的增加而下降。CHM处理甜菜幼苗9h后，随着浓度的增加和处理时间的延长，GS活性下降幅度增加，但GS1mRNA和GS2mRNA的相对量在不同CHM浓度处理间变化不显著。

英文摘要：

Glutamine synthetase （GS, EC6.3.1.2） families are the key enzymes involving in nitrogen assimilation in the higher plants as well as a core elements for nitrogen use efficiency and nitrogen recycle. The objective of this study was to reveal the effect of actinomycin D （AMD） and cycloheximide （CHM） on GS gene expression and its activities induced by nitrogen in sugar beet. GS activity in sugar beet was determined under the treatment of AMD and CHM. Gene transcripts of cytosolic glutamine synthetase （GS1） and plastidic glutamine synthetase （GS2） were detected by semi-quantitative PCR. Efficiency of GSmRNA synthesis from each sample was estimated by quantitative PCR of glyceraldehyde-3-phosphate dehydrogenase （GAPDH）. The results showed that the GS activities increased slightly under the low concentration treatment of AMD for 2-6 hours, but decreased with treatment of all concentrations. The transcript level of GS lmRNA and GS2mRNA decreased with the increase of AMD concentration treated for more than 9 hours. GS activities decreased fast with the increase of CHM concentrations treated for more than 9 hours. There was no significant difference between GSlmRNA and GS2mRNA expressions in the treatments with all CHM concentrations for more than 9 hours.