Comparative Analysis Of Gene Expression And Promoter Sequence In Rice Glutamine Synthetase

The activity of glutamine synthetase(GS)or gene expression was closely related to protein content in plant.Promoter is regarded as an important regulatory element controlling gene transcription on temporal and spatial level..In this experiment,Indica rice and Japonica Rice Varieties,significantly different in grain protein content,were used to analyze gene expression and promoter sequence and transcriptional regulation of glutamine synthetase(GS),to understand the structural features and function of GS gene promoter on transcription level,and to provide a theoretical basis for the molecular regulation of gene transcription.The main results are as follows:Transgressive variants can be obtained via directional selection from hybrid progenies with significantly different protein content.Protein content will be always higher in varieties with high protein content than that in varieties with low protein content at filling stage.This means grain protein content depends on genotypes.Moreover,the activity of glutamine synthetase in Indica Rice Cultivars was higher than that of transgressive variants and dual parents,and this activity is also higher in transgressive variants and parents with high grain protein content than that in transgressive variants and parents with lower protein content.GS isoform genes are tissue specific.GS1;1 and GS1;2 can be detected in grain and leaf,while GS1;3 is only detected in grain and GS2 is abundant in leaf.GS expression level was higher in high protein content cultivars than that in low protein content cultivars at filling stage.The expression level was closely related to the activity of enzyme and grain protein content in GS isoform genes.The activity of GS was positively correlated with protein content at filling stage,Os GS1;1expression is positively correlated with grain protein content at early and middle filling stage.Os GS1;1,Os GS2 and Os GS1;3 were positively correlated with protein content at filling stage,Os GS1;2 expression had a great influence on grain protein accumulation at the middle filling stage.Promoter sequence in GS genes was more conservative,above 99% similarity in rice cultivars with significantly different protein content.Base variation was found in GS promoter sequence in progenies from cultivar crossing,not in core elements.GS gene expression level was slightly regulated by its promoter.In the number and function of regulation elements,the promoter of GS gene has strong conservative property and is impossible to generate genetic variation in structure and function.GS gene expression was little affected by GS gene promoter.The promoter structure of GS iso-form genes was not completely consistent,and there were significant differences in the number of regulatory elements in different promoters,However,the promoter structure of GS promoter in different varieties was consistent.The expression of GS gene was related to many environmental factors.