XVI International Botanical Congess

To express a foreign genes efficiently in plant cells, we are developing the useful gene expression systems using cultured tobacco cells (BY2). Three cDNA clones, in which the mRNA level is high in log-phase cells, were isolated. And three cDNA clones, which are expressed in the stationary growth phase cells, were also isolated by a differential screening. Four promoters corresponding to the cDNAs were isolated and analyzed. Furthermore, a system for the controlled expression of a foreign gene by temperature shift was constructed. HSP18.2 promoter of Arabidopsis showed clear heat shock response of expression of the GUS reporter gene in BY2 cells. After a 2h induction by heat-shock, GUS activity was about 1000-fold greater than that before heat-shock.