Effects of spermine and plant hormones on nuclear protein phosphorylation in Ranunculus petioles

In isolated nuclei, polyamines were found to stimulate the phosphorylation of a 17.5, a 26, a 30 and a 35 kDa proteins. Spermine exhibited the most pr onounced effect on protein phosphorylation among the polyamines tested for the 17.5 and 35 kDa proteins. Results of protein phosphorylation patterns i n nuclei isolated from petiole tissue pretreated with IAA, ethylene, or spe rmine indicate that pretreatments with IAA and ethylene result in dephospho rylation of the 30 kDa protein, while spermine pretreatment leads to phosph orylation. For the soluble (cytosolic) fraction, spermine causes dephosphor ylation of a 34 kDa protein, while auxin and ethylene have no effect on thi s process. These results suggest that there is correlation between phosphor ylation/dephosphorylation of the 30 kDa nuclear protein and the control of cell growth in Ranunculus petioles.