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Issue Environ. Biosafety Res.
Volume 8, Number 2, April-June 2009
Page(s) 113 - 119
DOI 10.1051/ebr/2009015
Published online 22 October 2009

Environ. Biosafety Res. 8 (2009) 113-119
DOI: 10.1051/ebr/2009015

Stability of Cry1Ab protein during long-term storage for standardization of insect bioassays

Hang Thu Nguyen and Johannes A. Jehle

Agricultural Service Center Palatinate (DLR Rheinpfalz), Department of Phytopathology, Laboratory for Biotechnological Crop Protection, Breitenweg 71, 67435 Neustadt an der Weinstrasse, Germany

Received January 9, 2009; Accepted May 28, 2009; published online 22 October 2009

Abstract - The reliable use of purified Cry1Ab protein standards is a prerequisite for ecological studies and resistance monitoring programs of Cry1Ab-expressing transgenic corn. In this study the stability and activity of different Cry1Ab protein batches expressed in and purified from Escherichia coli were determined during two-year storage at different temperature conditions (4 °C, –20 °C, and –80 °C). SDS-Polyacrylamide gel electrophoresis showed degradation of the protein stored at 4 °C over four months, whereas no difference in the band intensity of the Cry1Ab proteins stored at –20 °C and –80 °C was observed. Bioassays with neonate larvae of Ostrinia nubilalis indicated that the biological activity of Cry1Ab varied from batch to batch, depending on the production process. Cry1Ab protein stored at 4 °C for four months showed a significantly decreasing activity measured as median lethal concentration (LC50), whereas the protein activity declined less than 11-fold after two years storage at –20 °C. When stored at –80 °C the toxin activity remained relatively stable for at least 30 months, as indicated by low LC50 values of 7–10 ng Cry1Ab per cm2 diet. These experiments demonstrate that appropriate long-term storage conditions of Cry1Ab protein standards are crucial for resistance monitoring programs of Bt corn, and storage at –80 °C is recommended.


Key words: Bt corn / Ostrinia nubilalis / resistance monitoring / bioassay

Corresponding author: johannes.jehle@dlr.rlp.de

© ISBR, EDP Sciences 2009


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