Monitoring transgene expression levels in different genotypes of field grown maize (Zea mays L.)

Transgenes in commercially available genetically modified plants are generally controlled by strong constitutive promoters to ensure a high level of expression at all stages of cultivation. Constitutive promoters however are influenced by a wide range of factors, and expression profiles of the transgenes in multiple genetic backgrounds have not yet been extensively studied. In this study a powerful expression profiling methodology for transgenic maize (Zea mays L.) is demonstrated on a large scale, analysing thousands of data points from three genotypes of herbicide and insect pest tolerant transgenic maize. Martonvasar inbred lines were crossed with LH244 maize line containing the MON 88017 events, and leaf tissue from the sixth backcross generation was sampled at four relevant phenological phases. Relative expression levels were determined using 18S rRNA as a reference and detailed statistical analysis performed. Expression levels of both transgenes are varied throughout plant development, and the interaction between the genetic background and phenophase are significant (p<0.05). Expression is present at a significant level throughout all the phenological stages. We found that the genetic background has a significant (p<0.01) effect on transgene expression levels in the case of the CP4epsps transgene, but not in the case of cry3Bb1, implying that the sensitivity of different constitutive promoter constructs to the effects of the genetic background is different. (c) 2012 SAAB. Published by Elsevier B.V. All rights reserved.