Effect of osmotic stress conditions on BvSTI-expressing Lotus corniculatus

Abstract

Plant proteinase inhibitors (PIs) constitute a large and complex widely distributed group of small proteins involved in the regulation of the plant protein turn-over required in multiple physiological processes. Beside the roles regarding development and physiology, PIs are known to act in defense against herbivore insect pests. In recent years, the new intriguing role of plant PIs in abiotic stress tolerance has been implied. Inhibitor of serine type proteinases, BvSTI isolated from sugar beet pest resistant genotype was introduced into Bird’s foot trefoil (Lotus corniculatus L.). To determine the effect of osmotic stress on BvSTI-expressing L. corniculatus, in vitro-grown shoots were exposed to elevated concentration of sucrose (5%, 7% and 9%). After 15 days of treatment, the growth response of sucrose-treated transformed lines 21, 73 and 109, as well as of nontransformed (NTC) line was determined by measuring the fresh weight and the length increment. Also shoots were scored for visible symptoms of osmotic stress-induced injuries by visual inspection. In order to avoid influence of observed phenotypic differences among lines on parameters analyzed under stress conditions, all values were presented relative to the controls (shoots grown under the same conditions on regular 3% sucrose) of each line. Additionally, the activities of antioxidant enzymes peroxidases (POD) and catalases (CAT) were determined spectrophotometrically.