Impact of salinity-tolerant MCM6 transgenic tobacco on soil enzymatic activities and the functional diversity of rhizosphere microbial communities.

The development of genetically modified plants for agriculture has provided numerous economic benefits, but has also raised concern over the potential impact of transgenic plants upon the environment. The rhizosphere is the soil compartment that is directly under the influence of living roots; it constitutes a complex niche likely to be exploited by a wide variety of bacteria potentially influenced by the introduction of transgenes in genetically modified plants. In the present study, the impact of overexpression of the salinity stress-tolerant minichromosome maintenance complex subunit 6 (MCM6) gene upon functional diversity and soil enzymatic activity in the rhizosphere of transgenic tobacco in the presence and absence of salt stress was examined. The diversity of culturable bacterial communities and soil enzymes, namely, dehydrogenases and acid phosphatases, was assessed and revealed no significant (or only minor) alterations due to transgenes in the rhizosphere soil of tobacco plants. Patterns in principal components analysis showed clustering of transgenic and non-transgenic tobacco plants according to the fingerprint of their associated bacterial communities. However, the presence of MCM6 tobacco did not cause changes in microbial populations, soil enzymatic activities or the functional diversity of the rhizosphere soil microbial community.