ACCUMULATION OF A 50-KDA PROTEIN DURING LEAF SENESCENCE OF ALSTROEMERIA CUT FLOWERING STEMS

Leaf senescence of alstroemeria cut flowering stems in the dark was ac companied by a decrease in the soluble protein and chlorophyll content . Two-dimensional (2D) electrophoresis revealed that a polypeptide wit h an apparent molecular mass of 50 (+/- 2) kDa and isoelectric point o f 5.0 (+/- 0.1) accumulated during the senescence process. Treatments which delayed leaf senescence (light and gibberellic acid) diminished the accumulation of this polypeptide. This polypeptide was purified an d one of the peptides, resulting from digestion with trypsin, was sequ enced. The sequence shows a high degree of homology to that of 3-isopr opylmalate dehydrogenase. This enzyme plays a role in the biosynthesis of leucine. Possibly, leucine plays a role in carbon partitioning bet ween sources and sinks in this plant.