Constitutive expression of Cry proteins in roots and border cells of transgenic cotton

Abstract

Transgenic cotton plants expressingCry1Ac and Cry2Ab, from the soil bacterium Bacillus thuringiensis (Bt), provide effective control of certain lepidopteran pests, however, little is known about the proteins below ground expression. We used ELISA to quantify in vitro expression of the Cry1Ac and Cry2Ab proteins in mucilage, root border cells and root tips in five transgenic cultivars of cotton compared to conventional cultivar Sicot 189. Expression of Cry proteins in roots and border cells of the transgenic cotton cultivars was constitutive and at detectable levels, with Cry1Ac and Cry2Ab protein expression ranging from <20 ppb to >100 pbb. To determine if genetically modified cotton demonstrated simple differences in properties of the root, when compared to an elite parental line (cv. Sicot 189), we enumerated border cells on seedling radicles. Border cell counts of 14 cultivars ranged from 0.2 to 1.1 · 10 4 cells per root tip with an average of 5 · 10 3 border cells. Border cell production in the transgenic cultivars was generally similar to that of both donor and elite parents, the exception being the cultivar Sicot 189, which had substantially more border cells than all of its transgenic derivatives. Comparison of border cell number with varietal disease resistance ranking found a limited relationship (r 2 = 0.65, n = 7) between border cell numbers and the commercial resistance rank against Fusarium wilt of cotton. The implications of differences in cotton cultivar border cell number and root tip expression of Cry proteins for plant-microbe interactions in the rhizosphere and the soil ecosystem are yet to be resolved.

Bt cotton planting does not affect the community characteristics of rhizosphere soil nematodes

“…However, Bt proteins, such as Cry1Ab and Cry1Ac, can be released into the soil from cotton residues, root exudates and pollen during growth and after harvest (Gupta and Watson, 2004;Knox et al, 2007). As the growing cultivation acreage of transgenic Bt cotton, the environmental impact monitoring after commercial release has attracted increasing attention from public and the scientific community.…”

“…Due to its promising effect on pest suppression, the total cultivation acreage of Bt cotton has expanded dramatically in northern China since 1997 (Huang and Pray, 2002). However, Bt proteins such as Cry1Ac and Cry1Ab produced in leaves, pollen and roots of Bt cotton can be introduced to soil through biomass incorporation and root exudates (Gupta and Watson, 2004;Knox et al, 2007;Li et al, 2012;Mina et al, 2008). Once released in soil, Bt toxin get adsorbed or bound on clay particles, humic components, or organic mineral complexes and in this way is protected against degradation by soil microorganisms (Tapp et al, 1995).…”

Do genetically modified plants impact arbuscular mycorrhizal fungi?

“…Dong et al (2006) showed new evidence that the Bt crystal proteins were mostly located in the cytoplasm and intercellular space of Bt transgenic cotton GK-12 cotyledon mesophyll cells, which provides indirectly evidence for the above intraradical damage mechanism. Knox et al (2007) used ELISA to quantify in vitro expression of the Cry1Ac and Cry2Ab proteins in mucilage, root border cells and root tips in five transgenic cultivars of cotton compared to conventional cultivar Sicot 189. Expression of Cry proteins in roots and border cells of the transgenic cotton cultivars was constitutive and at detectable levels, with Cry1Ac and Cry2Ab protein expression ranging from\20 to[100 pbb.…”

Improving Environmental Loading Assessments of Cry Protein from GM Plants Based on Experimentation in Cotton~!2008-09-12~!2008-11-15~!2008-12-05~!

“…Ground corn powder (Monsanto, Australia), previously used in published ELISA and bioassay studies [21,22], was found to produce a reliable standard over the range of 0.3 to 70 PPB (y= -12.7x 2 + 62.0x + 0.5, R 2 = 0.99, n=15). However, it was found to be susceptible to freeze/thawing, thus aliquots and dilutions were prepared fresh when required.…”