DEMONSTRATION OF A SENESCENCE COMPONENT IN THE REGULATION OF THE MANNOPINE SYNTHASE PROMOTER

Regulation of the mannopine synthase (mas) promoter during senescence in leaves and flowers of tobacco (Nicotiana tabacum) plants was invest igated. In plants transformed with a mas 5'-beta-glucuronidase (GUS)-m as 3' transcriptional fusion, we observed that following the onset of senescence in either intact or excised leaves of the transgenic lines, GUS activity increased significantly, whereas in excised leaves in wh ich the senescence process was inhibited, GUS activity increased only marginally. During flower petal senescence in the transgenic tobacco, GUS activity increased approximately 6-fold over preanthesis- and anth esis-stage flowers.