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 investigated. In plants transformed with a mas 5[prime]-[beta]-glucuronidase (GUS)-mas 3[prime] 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 which 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 anthesis-stage flowers.