INFLUENCE OF WOUND INJURY ON ACCUMULATION OF PROTEINASE INHIBITORS IN LEAF AND STEM TISSUES OF TWO PROCESSING TOMATO CULTIVARS

Abstract

Serine proteinase inhibitor(s) and small amounts of cysteine proteinase inhibitor were detected in both leaf and stem tissue 48 h after mechanical injury to the lower leaf of 21-25 day old tomato cultivars (cv). Leaves accumulated about 2-15 times more trypsin inhibitor than stem tissue. Approximately 10 times more trypsin inhibitor (TIU) accumulated in plants held at 30C in continuous light compared to plants held under ambient greenhouse conditions after injury. Uninjured plants held at 30C under continuous light accumulated lessproteinase inhibitor(s) than injured plants. Holding Bonnie Best in the dark at 30C for 48 h resulted in less inhibitor(s) accumulation in response to mechanical wounding than holding plants at 30C in continuous light. TIU/g tissue recovered from injured plants held at 30C under continuous light varied with cultivar, i. e., for leaves : Bonnie Best (33.61), Alta (21.00 ; 25. 3), Castlemart (16.00 ; 13.17) and Halley (1.96) ; and for stems : Castlemart (8.29), Alta (4.47) and Bonnie Best (2.59). SDS-PAGE assayed for inhibitor activity revealed the main trypsin and chymotrypsin inhibitor(s) in injured leaves both had a molecular mass (Mr) of 19.1 KD on SDS-PAGE substrate gels. Treatment of the inhibitors with 2.0% SDS at 100C prior to electrophoresis revealed a second major trypsin inhibitor (Mr = 16.4 KD) and two additional major α-chymotrypsin inhibitors (Mr = 16.4 ; 6.2 KD).