Root Acid Invertase Activity in a Transgenic Maize Isoline
Date of Award
Restricted Access Thesis
College of Theology, Arts, & Sciences
Math & Science
Dr. Sergei Polozov
Nontarget effects of genetically modified (GM) plants, such as those engineered to express Cry proteins from Bacillus thuringiensis (Bt), have yet to be fully characterized. Arbuscular mycorrhizal fungi (AMF) are especially susceptible to these effects due to their reliance on plant hosts and their root exudates for carbon. This AMF carbon allocation is partially regulated by root apoplast acid invertase, which cleaves sucrose, the major transport sugar, into hexoses that colonizing AMF are able to utilize. This study explored AMF colonization and root apoplast acid invertase activity in a genetically modified Bt-maize line (Event Bt 11) and its parental isoline (P), with and without AMF inoculation, to test the hypothesis that a reduction in invertase activity in Bt-maize is a potential mechanism regulating colonization by AMF, as pilot studies under nutrient stress suggested. Bt 11 (B) and P maize seeds were planted in a field soil based potting mix with AMF (+) or without AMF (-); whole plants were harvested after 30 days growth in a greenhouse. Root samples were incubated with sucrose, then tested with the DNS reaction and photometric analysis for reducing sugar concentration. There was no detectable difference in invertase activity between B and P cultivars, but activity was significantly lower in (+) than the (-) treatments. The reduction in (+) plants suggests down-regulation of invertase; future studies will determine whether this reduction in invertase activity may be attributed to pathogen stress or a reduced ability to either up- or down-regulate invertase levels in the Bt 11 isoline.