SUGAR RESPONSE ELEMENT ENHANCES WOUND RESPONSE OF POTATO PROTEINASE INHIBITOR-II PROMOTER IN TRANSGENIC TOBACCO

The promoter region of the potato proteinase inhibitor II (PI-II) gene was studied to identify cis-acting regulatory sequences involved in sugar response using transgenic tobacco plants. The 5' control region covering an 892 nucleotide sequence upstream from the cap site and a 32 nucleotide untranslated region of the PI-II promoter was able to activate a reporter chloramphenicol acetyltransferase (cat) gene by wounding or by incubating in a sugar-free medium. This wound response was further enhanced by sugar. Hexoses, disaccharides, and some trisaccharides were strong inducers whereas pentoses, deoxy sugars, sugar acids, TCA cycle intermediates, amino acids, and other carbohydrates had little effect on the promoter activity. Deletion of the sequence between -892 and -573 abolished the wound response but not the sugar response. An additional 5' deletion to -453 removed the sugar inducibility. Locations of the cis-acting regulatory elements were further elucidated by 3' deletion analysis. Deletion of the downstream region from -520 did not affect the wound or sugar response of the promoter. However, 3' deletion mutant -574 was unable to respond to sugar but did respond weakly to wounding. Further deletion to -624 abolished both responses. Therefore, it can be concluded that a wound response element is located in between -624 and -574 and that the response is further enhanced by a sugar response element located in the sequence between -573 and -520.