Elicitation of peroxidase activity in genetically transformed root cultures of Beta vulgaris L.

Abstract

Genetically transformed roots of red beet produce copious levels of peroxidase (POD) - a multifunctional enzyme with a number of commercial applications. In an effort to elicit the POD activity, the cultures were treated with biotic elicitors such as dry cell powders of microbial cultures (0.1-0.5% w/v) and the respective culture filtrates (1-5% v/v). Similarly, abiotic elicitors, particularly metal ions (2-8 folds of that present in the nutrient medium), the plant hormone Thidiazuron (at 0.25-1 ppm) and other bio-molecules such as Glutathione (at 0.5-10 mM) and Methyl jasmonate (at 20-100 µM) were used. It was observed that dry cell powder of Candida versatilis significantly elicited the enzyme activity (3.52-fold higher than the control) followed by glutathione (3.44-fold) and Rhizophus oligosporus (3.09-fold). Among abiotic elicitors, thidiazuron, Mg and Ca salts elicited 2.49, 3.03 and 2.8 fold activities respectively. While most of the biotic elicitors were effective when added on 15^th day of culture, the abiotic elicitors were effective when added on 20^th day. Combination of highly effective elicitors indicated that glutathione (1 mM) and dry cell powder of R. oligosporus caused a 4-fold enhancement in enzyme activity, accounting for 10.9 x 10⁶ U L^-1. The present study is the first report on red beet hairy roots where a large number of elicitors have been systematically screened and their probable involvements in eliciting POD activities have been discussed.