Molecular genetic analysis of sugar-inducible gene expression in plant.

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Regulations of storage and partitioning of plant nutrients like as carbon and nitrogen are correlated with the productivity of crops. Many genes in this system are regulated with the concentration of sugars supplied to plant tissues. In this study, we established a new system for screening of mutant of Arabidopsis thaliana to analyze the factors involving this regulation.The expression revel of the gene for a storage protein, sporamin that exists predominantly in tuberous root of sweet potato is induced by the supply of high concentration of sugars. Our analysis of promoter region of this gene by using transgenic tobacco revealed that two cis-regulatory elements are necessary to this regulation.AG221-promoter is a promoter which removed unnecessary region of original sporamin promoter and whose responsibility to sugar-level is highly apparent, compared with original promoter. We constructed a transcriptional Luciferase (LUG) fusion gene in which AG221 promoter was fused with LUC coding region and introduced this fusion gene into the genome of Arabidopsis thaliana. This fusion gene was activated in 24h after treatment of high concentration of matabolitable sugar like as sucrose and fructose with a concentration dependent manner.A transgenic line containing the fusion gene was introduced mutations with EMS and mutants were screened from the descendants. We got 29 lines of mutants which have strong LUC activity with the treatment with 0% and 6% sucrose, 19 lines of mutants which have no LUC activity and 25 lines of mutants which have very low activity when tissue was treated with high concentration of sugars.