Abstract
The photosynthesis mode of M. crystallinum is changed from C3 to crassulacean acid metabolism (CAM) within 10 days after onset of water stress when the plant age is 5 week old. Transcripts of many CAM-related genes increase during the CAM induction. To clarify the transcriptional regulation mechanism of a CAM-inducible gene, McGPT2 coding a plastidic glucose-6-phosphate/Pi translocator, we joined the -2.6 kb upstream region from the transcriptional start site of McGPT2 and its 5' deletion mutants to the firefly luciferase ORF. Transient expression studies with these constructs using M. crystallinum leaf tissues suggested that cis factors of the CAM induction and diurnal regulation were located within a region -0.24 kb upstream from the transcriptional start site and a region from -0.24 to -0.7 kb, respectively. The CAM induction of M. crystallinum takes more than 15 days after onset of the water stress if the plant age is 4 week old, which is much smaller than 5-week-old plants. We found that the increment of the McGPT2 promoter activity was also delayed much in the stressed 4-week-old plants suggesting that the CAM induction is affected developmentally at transcriptional level.
