Effects of Photosystem-II-Interfering Herbicides Atrazine and Bentazon on the Soybean Transcriptome

Atrazine and bentazon are both photosystem-II (PSII)-inhibiting herbicides that interfere with photosynthetic electron transport, provoking oxidative stress. While atrazine is lethal to soybean [Glycine max (L.) Merr.], bentazon does not kill soybean because of the capability of soybeans to metabolize the herbicide. Gene expression profiling was conducted using cDNA microarrays to understand the responses of soybeans to PSII interruption and concomitant stress caused by atrazine and bentazon by monitoring expression at 1, 2, 4, and 8 h after treatment (HAT). The microarray study revealed that 6646 genes were differentially expressed with high statistical significance over the experiment, with 88% of them sharing similar expression pattern between the atrazine and bentazon treatments. Many genes related to xenobiotic detoxification and antioxidation, such as cytochrome P450s, glutathione-S-transferases, superoxide dismutases, catalases, and tocophero cyclases, were induced by the herbicides. The study also discovered plants treated with bentazon started to recover between 4 and 8 HAT as reflected in the decreased amplitude of fold changes of most genes from 4 to 8 HAT. The 12% of the genes that were differentially expressed between atrazine and bentazon were largely related to cell recovery, such as genes related to ribosomal components.