A PROMOTER FOR STRONG AND UBIQUITOUS ANAEROBIC GENE-EXPRESSION IN TOBACCO

The maize GapC4 promoter confers strong and ubiquitous anaerobic expre ssion of the beta-glucuronidase reporter gene in transgenic tobacco. A mong 21 transgenic tobacco lines harboring 785 or 461 bp from the GapC 4 promoter, 18 show anaerobic gene expression, In six lines anaerobic fluorescence values were more than 1000-fold over nonspecific backgrou nd and in five lines anaerobic gene expression exceeded aerobic expres sion of a reporter gene construct under the control of the strong caul iflower mosaic virus 35S promoter, Aerobic gene expression was detecte d in only three lines. Anaerobic induction is observed in all tissues including mature leaves and flowers and is transcriptionally induced w ithin at least 12 h. Within 3 h of transfer of tobacco seedlings from anaerobic to aerobic conditions reporter gene transcription is turned off. Among other environmental factors only wounding and UV light resu lt in a 10- to 40-fold induction of reporter gene expression above bac kground. The strong inducibility, mode of expression under non-inducin g conditions, the specificity, and the ubiquitous induction distinguis hes the GapC4 promoter from all previously analyzed anaerobic promoter -reporter gene constructs.