PROMOTERS FROM GENES FOR PLASTID PROTEINS POSSESS REGIONS WITH DIFFERENT SENSITIVITIES TOWARD RED AND BLUE-LIGHT

The light-regulated expression of eight nuclear-encoded genes for plas tid proteins from spinach (Spinacia oleracea) (RBCS-1 and CAB-1; ATPC and ATPD, encoding the subunits gamma and delta of the ATP synthase; P C and FNR; PSAD and PSAF, encoding the subunits II and III of photosys tem I reaction center) was analyzed with promoter/beta-glucuronidase ( GUS) gene fusions in transgenic tobacco (Nicotiana tabacum and Nicotia na plumbaginifolia) seedlings and mature plants under standardized lig ht and growth conditions. Unique response patterns were found for each of these promoters. GUS activities differed more than 30-fold. Strong promoters were found for the PC and PSAD genes. On the other hand, th e ATPC promoter was relatively weak. Expression of the CAB/GUS gene fu sion in etiolated material was at the detection limit; all other chime ric genes were expressed in the dark as well. Light stimulation of GUS activities ranged from 3- (FNR promoter) to more than 100-fold (CAB-1 promoter). The FNR promoter responded only to red light (RL) and not significantly to blue light (BL), whereas the PC promoter contained re gions with different sensitivities toward RL and BL. Furthermore, diff erent RNA accumulation kinetics were observed for the PSAF, CAB, FNR, and PC promoter/GUS gene fusions during de-etiolation, which, at least in the case of the PSAF gene, differed from the regulation of the cor responding endogenous genes in spinach and tobacco. The results sugges t either that not all cis elements determining light-regulated and qua ntitative expression are present on the spinach promoter fragments use d or that the spinach cis-regulatory elements respond differently to t he host (tobacco) regulatory pathway(s). Furthermore, as in tobacco, b ut not in spinach, the trans-gene hardly responds to single light puls es that operate through phytochrome. Taken together, the results sugge st that the genes have been independently translocated from the organe lle to the nucleus during phylogeny. Furthermore, each gene seems to h ave acquired a unique set of regulatory elements.