SPECIFIC PROTEIN OCCURRENCE RELATED WITH PHOTOPERIODIC FLOWER INDUCTION IN THE COTYLEDONS OF Pharbitis nil CV. VIOLET

Abstract

In our experiment, three groups of seedlings of SDP Pharbitis nil cv. violet were sepa- rately treated with three different photoperiods (1,16 h dark period--SD; 2, continuous illumi- nation--CL; 3, 16 h dark treatment with 10 min white light in the middle of the dark period --NB). By analysing proteins in the cotyledons from three groups with 2-D PAGE, we found no difference in protein pattern between the three groups at 0 or 8 h after photoperiodic treatments. At 24 h after the treatments, a specific protein(MW:19 kD; pI: 4.5)appeared only in the cotyledons of the seedlings which endured SD. This protein disappeared at 72 h after SD. Actinomycin D could inhibit flowering and the specific protein occurrence when applied to cotyledons prior to SD, but it had no inhibition effect on flowering as well as the specific protein occurrence when applied to cotyledons after SD. Chloroamphenicol, a protein synthesis inhibitor, inhibited flowering when applied to cotyledons prior to or immediately after SD, but it did not inhibit flowering when applied to cotyledons at 24 h after SD. With the joint consideration of the effects of defoliation and inhibitor applications on flowering, we deduced that the 19 kD protein occurrence correlated with the commitment to flowering. The gene transcription related with induction was fulfilled within the SD period, while the specific protein synthesis lasted 24 h after SD. The key regulation step of biochemical changes during induction was at the transcriptional level.