The present invention provides novel eukaryotic DNA sequences coding for native protoporphyrinogen oxidase (protox) or modified forms of the enzyme which are herbicide tolerant Plants having altered protox activity which confers tolerance to herbicides are also provided These plants may be bred or engineered for resistance to protox inhibitors via mutation of the native protox gene to a resistant form or through increased levels of expression of the native protox gene, or they may be transformed with modified eukaryotic or prokaryotic protox coding sequences or wild type prokaryotic protox sequences which are herbicide tolerant Diagnostic and other uses for the novel eukaryotic protox sequence are also described Plant genes encoding wild-type and altered protox, purified plant protox, methods of isolating protox from plants, and methods of using protox-encoding genes are also disclosed

Manipulation of protoporphyrinogen oxidase enzyme activity in eukaryotic organisms

The use of herbicides to control undesirable vegetation has become a universal practice. For the broad application of herbicides the risk of damage to crop plants has to be limited. We introduced a gene into the genome of tobacco (Nicotiana tabacum) plants encoding the plastid-located protoporphyrinogen oxidase of Arabidopsis, the last enzyme of the common tetrapyrrole biosynthetic pathway, under the control of the cauliflower mosaic virus 35S promoter. The transformants were screened for low protoporphyrin IX accumulation upon treatment with the diphenyl ether-type herbicide acifluorfen. Leaf disc incubation and foliar spraying with acifluorfen indicated the lower susceptibility of the transformants against the herbicide. The resistance to acifluorfen is conferred by overexpression of the plastidic isoform of protoporphyrinogen oxidase. The in vitro activity of this enzyme extracted from plastids of selected transgenic lines was at least five times higher than the control activity. Herbicide treatment that is normally inhibitory to protoporphyrinogen IX oxidase did not significantly impair the catalytic reaction in transgenic plants and, therefore, did not cause photodynamic damage in leaves. Therefore, overproduction of protoporphyrinogen oxidase neutralizes the herbicidal action, prevents the accumulation of the substrate protoporphyrinogen IX, and consequently abolishes the light-dependent phytotoxicity of acifluorfen.

Overexpression of Plastidic Protoporphyrinogen IX Oxidase Leads to Resistance to the Diphenyl-Ether Herbicide Acifluorfen

The present invention provides novel eukaryotic DNA sequences coding for native protoporphyrinogen oxidase (protox) or modified forms of the enzyme which are herbicide tolerant. Plants having altered protox activity which confers tolerance to herbicides and a method of selecting transformed plants are also provided.

Methods of selecting plants, plant tissue or plant cells resistant to a protoporphyrinogen oxidase inhibitor

The present invention provides novel DNA sequences coding for plant protoporphyrinogen oxidase (protox) enzymes from soybean, wheat, cotton, sugar beet, grape, rice and sorghum. In addition, the present invention teaches modified forms of protox enzymes that are herbicide tolerant. Plants expressing herbicide tolerant protox enzymes taught herein are also provided. These plants may be engineered for resistance to protox inhibitors via mutation of the native protox gene to a resistant form or they may be transformed with a gene encoding an inhibitor-resistant form of a plant protox enzyme.

Dna molecules encoding plant protoporphyrinogen oxidase and inhibitor-resistant mutants thereof

The present invention provides novel DNA sequences coding for protoporphyrinogen oxidase (protox) enzymes from soybean, wheat, cotton, sugar beet, oilseed rape, rice, sorghum, and sugar cane. In addition, the present invention teaches modified forms of protox enzymes that are herbicide tolerant. Plants expressing herbicide tolerant protox enzymes taught herein are also provided. These plants may be engineered for resistance to protox inhibitors via mutation of the native protox gene to a resistant form or they may be transformed with a gene encoding an herbicide tolerant form of a plant protox enzyme.

Rong Guo

Papers

High-performance liquid chromatographic assays for protoporphyrinogen oxidase and ferrochelatase in human leucocytes