Isolation, Characterization of A Fruit Specific Promoter Sequence of A Thaumatin Gene Coding for Fruit Ripening Protein Differentially Expressed in Storage Fruit

Most proteins are tasteless and flavorless, while some proteins elicit a sweet-taste on the human palate. Thaumatin is one of the most potently sweet properties, are derived from a plant in tropical Africa and elicit a sweet taste response at a concentration approximately 100, 000 fold higher than of sucrose on a molar basis. The biotechnological production of sweet protein would provide valuable information on the mechanism underlying the elicitation of sweetness in protein as well as the interaction between sweet-tasting protein and their putative receptors. Transgenic technologies can be useful for increasing its sweetening value and its expression in other plant having low sweetening value. However, tissue-specific promoters that guarantee correct expression of transgenes would be necessary. We used polymerase chain reaction to isolate a promoter sequence of the thaumatin gene coding for fruit ripening protein differentially expressed in storage fruit. In silico analysis revealed putative cis-acting regulatory elements within this promoter sequence, including fruit-specific elements that may be required for its expression in vascular tissues. Transient expression experiments showed that the thaumatin promoter is functional, since this sequence was able to drive GUS expression in grapes fruit. Results from our computational analysis can serve as a guide for functional experiments to identify regions with tissue-specific thaumatin promoter activity. The DNA sequence that we identified is a new promoter that could be a candidate for genetic engineering of different fruit yielding plant.