High Antioxidant Ability Confer Resistance to Atrazine in Commelina communis L

Sensitivity and antioxidant response of forest species seedlings to the atrazine under simulated conditions of subsurface water contamination

Atrazine is an herbicide with a high soil leaching capacity, contaminating subsurface water sources. Once the water table is contaminated, riparian species can be exposed to atrazine. In this way, understanding the impacts of this exposure must be evaluated for planning strategies that minimize the effects of this herbicide on native forest species. We aimed to evaluate forest species' sensitivity and antioxidant response to exposure to subsurface waters contaminated with atrazine, as well the dissipation this herbicide. The experiment was conducted in a greenhouse in a completely randomized design, with three replications and one plant per experimental unit. The treatments were arranged in a 2 × 10 factorial. The first factor corresponded to the presence or absence (control) of the atrazine in the subsurface water. The second factor comprised 10 forest species: Amburana cearensis, Anadenanthera macrocarpa, Bauhinia cheilantha, Enterolobium contortisiliquum, Hymenaea courbaril, Libidibia ferrea, Mimosa caesalpiniifolia, Mimosa tenuiflora, Myracrodruon urundeuva, and Tabebuia aurea. The forest species studied showed different sensitivity levels to atrazine in subsurface water. A. cearensis and B. cheilantha species do not have efficient antioxidant systems to prevent severe oxidative damage. The species A. macrocarpa, E. contortisiliquum, L. ferrea, and M. caesalpiniifolia are moderately affected by atrazine. H. courbaril, M. urundeuva, and T. aurea showed greater tolerance to atrazine due to the action of the antioxidant system of these species, avoiding membrane degradation events linked to the production of reactive oxygen species (ROS). Among the forest species, H. courbaril has the most significant remedial potential due to its greater tolerance and reduced atrazine concentrations in the soil.

PsbA gene over-expression and enhanced metabolism conferring resistance to atrazine in Commelina communis

Commelina communis L. is a troublesome weed in agronomic fields and increasingly threatens the yield security of corn in north-eastern China. Previously, we found that a C. communis population (JL-1) has evolved resistance to atrazine. Although the potential genetic and enzymic differences contributing to atrazine resistance in this population have been investigated, the specific molecular mechanisms underlying C. communis resistance are still poorly understood. Here, the expression level of the target gene PsbA and the non-target-site resistance (NTSR) mechanism for this population were studied. The results showed that the decline in chlorophyll content in JL-1 leaves was less than in the susceptible JS-10 population following atrazine treatment. JL-1 exhibited an enhanced expression of the PsbA gene compared with JS-10 of 7.28- and 14.28-fold higher at 0 and 24 h after treatment with atrazine, respectively. The cytochrome P450 monooxygenase (P450) inhibitor piperonyl butoxide (PBO) increased the phytotoxicity of atrazine in both populations of C. communis. Seven candidate genes associated with NTSR of Jl-1 were identified through RNA-seq and validated by quantitative real-time PCR, including 5 upregulated genes involved in herbicide metabolism. In addition, the activities of glutathione S-transferases and P450s in JL-1 were increased compared with JS-10. Collectively, PsbA gene overexpression and enhanced metabolism are likely to be responsible for JL-1 resistance to atrazine.