The plastidic Arabidopsis protoporphyrinogen IX oxidase gene, with or without the transit sequence, confers resistance to the diphenyl ether herbicide in rice

Agrobacterium-mediated gene transformation was used to introduce plastidic protoporphyrinogen IX oxidase (Protox) genes from Arabidopsis, with and without the transit sequence, into the rice genome. They were placed under the control of the constitutive and ubiquitous maize ubiquitin promoter, and their abilities to confer resistance to the diphenyl ether-type herbicide, oxyfluorfen were compared. The integration and expression of the transgene in the T₁ generation was examined by Southern, northern and western blot analyses. Surprisingly, as judged by an in vivo seed germination assay and an in vitro cellular leakage assay, both lines were similarly resistant to oxyfluorfen. The tolerance to cellular damage (lipid peroxidation and electrolyte leakage) was higher in transgenic plants than in wild-type plants. In transgenic plants, the degree of herbicide resistance varied directly with the absolute amount of Protox protein expression. Both the intact protein and the protein with the transit sequence deleted were accumulated in plastids.