PURIFICATION AND CHARACTERIZATION OF A THIOL-PROTEASE INDUCED DURING SENESCENCE OF UNPOLLINATED OVARIES OF PISUM-SATIVUM

A senescence-specific protease has been purified from senescent unpoll inated ovaries of Pisum sativum L. cv. Alaska by acidic extraction, (N H4)2SO4 fractionation, ion exchange chromatography on CM-Sephadex, and affinity chromatography on ribulose-1,5-bisphosphate carboxylase/oxyg enase (Rubisco)-Sepharose. Characterization of the purified protease i ndicated that it is a thiol-endoprotease (EC 3.4.22 class) active over a wide pH range. Purified antibodies against this protease inhibit th e degradation of Rubisco in autodigested extracts of senescent ovaries , suggesting that Rubisco might be a substrate for the protease in sen escent pea ovaries. The relative levels of the protease were determine d by an enzyme-linked immunosorbent assay (ELISA) along the processes of ovary senescence and gibberellic acid (GA)-induced fruit developmen t, indicating its induction at the beginning of senescence and the sup pression of its synthesis by GA treatment.