LIGHT-REGULATION OF PHOSPHOENOLPYRUVATE CARBOXYLASE MESSENGER-RNA IN LEAVES OF C4 PLANTS - EVIDENCE FOR PHYTOCHROME CONTROL ON TRANSCRIPTION DURING GREENING AND FOR RHYTHMICITY

The mechanism underlying the accumulation of specific RNA encoding the G form (photosynthetic) of phosphoenolpyruvate carboxylase (PEPC, EC 4.1.1.31) has been studied during the greening process of Sorghum and maize leaves. From a Γgt11 cDNA library, a cDNA clone for Sorghum leaf PEPC was identified, sequenced and found to correspond to the photosynthetic type of the protein by means of monoclonal antibodies. 'Run off transcription experiments showed that Sorghum or maize leaf nuclei extracted from light-grown plants produced considerably more PEPC mRNAs than those obtained from dark-grown plants. Ribosomal RNA and LHCP mRNAs increased concomitantly. 'Run off' analyses also indicated that transcription of these mRNAs was phytochrome-mediated. In plants grown in normal photoperiodic conditions, the PEPC-RNA pool followed a rhythmical behaviour, being low at night and recovering its maximum level the following day. However, after 24 h of dark treatment, both the RNA pool and the transcription capacity were found to be strongly decreased. In contrast, the PEPC protein remained constant during the same developmental period. © 1990.