γ-Aminobutyric acid (GABA) improves pesticide detoxification in plants

It is important to ensure food safety to study the technology and mechanism of pesticide residues degradation in crops. Though γ-aminobutyric acid (GABA) has been widely reported to involve in plant stress resistance, whether exogenous application or endogenous regulation of GABA by gene-editing technology can promote the pesticide detoxification is not clear in plants. Using tomato and chlorothalonil (CHT) as research models, we discovered that exogenous application of GABA or endogenous elevation of GABA by knockout of pyruvate-dependent GABA transaminase promoted both CHT metabolism and plant stress tolerance to CHT. This is closely related to the active adaptation of GABA to CHT stress by regulating the plant GABA shunt pathway and polyamine pathway. The transcriptome data revealed 17 target genes that may be closely related to the involvement of GABA in CHT metabolism, including 4 peroxidases, 5 glycosyltransferases, 4 glutathione S-transferases, and 4 ABC transporters. In addition, the glutathione detoxification pathway and antioxidative enzyme also actively participated in the GABA-induced CHT detoxification process, which played an important role in relieving CHT stress. As a result, GABA significantly increased the photosynthetic capacity of tomato leaves under CHT stress. While studying photosynthesis, we unexpectedly found that GABA promotes stomatal closure in terms of decreased stomatal conductance and stomatal diameter. This result implies that GABA can reduce CHT absorption by regulating stomatal movement in leaves. Together, we provided a novel viewpoint that foliar application of GABA or metabolic engineering of GABA is an effective approach to reduce the risk of pesticide contamination in crop production.