FERREDOXIN-1 MESSENGER-RNA IS DESTABILIZED BY CHANGES IN PHOTOSYNTHETIC ELECTRON-TRANSPORT

In transgenic tobacco, pea Ferredoxin-1 (Fed-1) mRNA accumulates rapid ly in response to photosynthesis even when the transgene is driven by a constitutive promoter. To investigate the role of photosynthesis on Fed-1 mRNA stability, me used the tetracycline repressible Top10 promo ter system to specifically shut off transcription of the Fed-1 transge ne, The Fed-1 mRNA has a half-life of approximately 2.4 hr in the ligh t and a half-life of only 1.2 hr in the dark or in the presence of the photosynthetic electron transport inhibitor 3-(3,4-dichlorophenyl)-1, 1-dimethylurea (DCMU). These data indicate that cessation of photosynt hesis, either by darkness or DCMU results in a destabilization of the Fed-1 mRNA, Furthermore, the Fed-1 mRNA half-life is reduced immediate ly upon transfer to darkness, suggesting that Fed-1 mRNA destabilizati on is a primary response to photosynthesis rather than a secondary res ponse to long-term dark adaptation. Finally, the two different methods for efficient tetracycline delivery reported here generally should be useful for half-life measurements of other mRNAs in whole plants.