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Digestive proteolytic activity in larvae of tomato moth, Lacanobia oleracea; effects of plant protease inhibitors in vitro and in vivo

Lookup NU author(s): Professor Angharad MR Gatehouse, Gillian Davison

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Abstract

Three distinct digestive protease activities, with strongly alkaline pH optima, were identified in the gut of tomato moth (Lacanobia oleracea) larvae, and characterised using specific synthetic substrates and inhibitors. These were; a trypsin-like activity, a chymotrypsin-like activity specific for substrates and inhibitors containing more than one amino acid residue, and an elastase-like activity, accounting for 40%, 30% and 20% of overall proteolysis respectively. The protease activities differed in their sensitivities to inhibition by different plant protein protease inhibitors (PIs), as estimated by I-50 values. Soya bean Kunitz trypsin inhibitor (SKTI) was the only plant PI tested to inhibit all three digestive protease activities at concentrations <40 mu g/ml (approx. 5x10(-6)M). Incorporation of SKTI into a potato leaf-based artificial diet at 2% of total protein, decreased larval survival and growth (by approx. 33% and 40% respectively after 21 days) and retarded development (by approx. 2 days). However, when SKTI was expressed in transgenic potato plants at approx. 0.5% of total protein, only marginal effects on L. oleracea larvae were observed, which decreased with time. Whilst the presence of SKTI in artificial diet increased endogenous larval trypsin-like activity by up to four-fold, no effects on this activity were observed in larvae feeding on transgenic plants. (C) 1999 Elsevier Science Ltd. All rights reserved.


Publication metadata

Author(s): Davison GM; Gatehouse AMR; Norton E; Babbe SM; Newell CA; Gatehouse JA

Publication type: Article

Publication status: Published

Journal: Journal of Insect Physiology

Year: 1999

Volume: 45

Issue: 6

Pages: 545-558

Print publication date: 01/06/1999

ISSN (print): 0022-1910

ISSN (electronic): 1879-1611

Publisher: Elsevier Science Ltd.

URL: http://dx.doi.org/10.1016/S0022-1910(98)00161-9

DOI: 10.1016/S0022-1910(98)00161-9


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