Analysis of tomato seedling cell death in response to copper and paraquat induction

Plant defense responses to stress have attracted interest because of their similarity to reported mammalian stress responses. To investigate plant responses to abiotic stress, caspase 10-like enzymatic activities of Lycopersicon hirsutum and Lycopersicon esculentum were assayed in response to copper chloride and paraquat induction. Caspase 10-like activity was greatest at 40 mM CuCl2 at 9 h after elicitation in both L. hirsutum and L. esculentum, for which respective response slopes (Δ absorbance per Δ minute) were 0.0054 and 0.0022 . The response for L. hirsutum was less variable and significantly greater than for L. esculentum. Elicitation of caspase 10-like activity by paraquat was greatest at around 2 h after treatment in both species with slopes of 0.013 and 0.0012, respectively for L. hirsutum and L. esculentum. The direct determination of caspase 10-like activity in tomato seedlings treated with copper and paraquat, using a specific substrate for mammals, suggested that the observed responses were related to apoptosis processes under abiotic induction.