Biodegradation of atrazine by three transgenic grasses and alfalfa expressing a modified bacterial atrazine chlorohydrolase gene

Authors: VAIL, ANDREW - University Of Minnesota; WANG, PING - University Of Minnesota; UEFUJI, HIROTAKA - University Of Minnesota; Samac, Deborah - Debby; VANCE, CARROLL - University Of Minnesota; WACKETT, LAWRENCE - University Of Minnesota; SADOWSKY, MICHAEL - University Of Minnesota

Submitted to: Transgenic Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/16/2014
Publication Date: 6/1/2015
Publication URL: http://handle.nal.usda.gov/10113/60882
Citation: Vail, A.W., Wang, P., Uefuji, H., Samac, D.A., Vance, C.P., Wackett, L.P., Sadowsky, M.J. 2015. Biodegradation of atrazine by three transgenic grasses and alfalfa expressing a modified bacterial atrazine chlorohydrolase gene. Transgenic Research. 24:475-488.

Interpretive Summary: Herbicides are needed for control of weeds to obtain maximum crop productivity. The herbicide atrazine and other herbicides in this class are widely used for control of weeds in corn and sorghum production. Atrazine degrades slowly in soil and water and may accumulate to levels that are above the maximum contaminant level goals set by the Environmental Protection Agency. Economical and efficient ways to remediate contaminated soil and water are needed. Three grasses with extensive root systems, tall fescue, perennial ryegrass, and switchgrass, as well as the dicot legume alfalfa were engineered to express a gene isolated from bacteria that is the first step in the atrazine degradation pathway. All plants had increased resistance to atrazine compared to non-engineered plants. Alfalfa and tall fescue plants grew in soil or water with concentrations of atrazine found in the environment that are toxic to non-engineered plants, removed atrazine from water and soil, and converted atrazine to a non-herbicidal compound that accumulated within the plants. The plants also produced a novel compound from atrazine that was identified. Results of these studies indicate that these transgenic plants may be useful for the bioremediation of atrazine in the environment.

Technical Abstract: The widespread use of atrazine and other s-triazine herbicides to control weeds in agricultural production fields has impacted surface and ground water in the United States and elsewhere. We previously reported the cloning, sequencing, and expression of six genes involved in the atrazine biodegradation pathway of Pseudomonas sp. strain ADP, which is initiated by atzA, encoding atrazine chlorohydrolase. Here we explored the use of transgenic grasses (tall fescue, perennial ryegrass, and switchgrass) and the legume alfalfa expressing a modified bacterial atrazine chlorohydrolase, p-AtzA, for the biodegradation of atrazine in soil and water. Enhanced expression of p-AtzA in the grasses was obtained by using combinations of the badnavirus promoter, the maize alcohol dehydrogenase first intron, and the maize ubiquitin promoter. For alfalfa, we used the first intron of the 5’-untranslated region tobacco alcohol dehydrogenase gene and the cassava vein mosaic virus promoter. Resistance to atrazine in agar-based and hydroponic growth assays was linked to in vivo gene expression and atrazine degradation. The in planta expression of p-atzA enabled transgenic tall fescue to transform atrazine into hydroxyatrazine and other metabolites. Results of our studies indicate that these transgenic plants may be useful for the bioremediation of atrazine in the environment.