Adenosine triphosphate alleviates high temperature-enhanced glyphosate toxicity in maize seedlings

Abstract

Extracellular ATP plays a key role in regulating plants stress responses. Here, we aimed to determine whether ATP can alleviate the glyphosate toxicity in maize seedlings under high temperature by regulating antioxidant responses. Foliar spraying with 100 μM glyphosate inhibited the growth of maize seedlings at room temperature (25 °C), leading to an increase in shikimic acid accumulation and oxidative stress (evaluated via lipid peroxidation, free proline, and H2O2 content) in the leaves, all of which were further exacerbated by high temperature (35 °C). The growth inhibition and oxidative stress caused by glyphosate were both alleviated by exogenous ATP. Moreover, the glyphosate-induced antioxidant enzyme activity and antioxidant accumulation were attenuated by high temperature, while ATP treatment reversed this inhibitory effect. Similarly, qPCR data showed that the relative expression levels of antioxidant enzyme-related genes (CAT1, GR1, and γ-ECS) in maize leaves were upregulated by ATP before exposure to GLY. Moreover, high temperature-enhanced GLY residue accumulation in maize leaves was reduced by ATP. ATP-induced detoxification was attenuated through NADPH oxidase (NOX) inhibition. Higher NOX activities and O2•− production were noted in ATP-treated maize leaves compared to controls prior to GLY treatment, indicating that the extracellular ATP-induced alleviation of GLY toxicity was closely associated with NOX-dependent reactive oxygen species signalling. The current findings present a new approach for reducing herbicide toxicity in crops exposed to high temperatures.