Development of PPO inhibitor‐resistant cultures and crops

Abstract

Recent progress in the development of protoporphyrinogen oxidase (PPO, Protox) inhibitor-resistant plant cell cultures and crops is reviewed, with emphasis on the molecular and cellular aspects of this topic. PPO herbicide-resistant maize plants have been reported, along with the isolation of plant PPO genes and the isolation of herbicide-resistant mutants. At the same time, PPO inhibitor-resistant rice plants have been developed by expression of the Bacillus subtilis PPO gene via targeting the gene into either chloroplast or cytoplasm. Other attempts to develop PPO herbicide-resistant plants include conventional tissue culture methods, expression of modified co-factors of the protoporphyrin IX binding subunit proteins, over-expression of wild-type plant PPO gene, and engineering of P-450 monooxygenases to degrade the PPO inhibitor.

A codon deletion confers resistance to herbicides inhibiting protoporphyrinogen oxidase

“…Second, the specific alteration of PPO2L that confers resistance to PPO-inhibiting herbicides is an amino acid deletion, rather than a substitution, resulting from a 3-bp deletion in the gDNA. Although intentional selection for resistance to PPO inhibitors identified amino acid substitutions that conferred resistance (20,29), the codon-deletion approach revealed by A. tuberculatus is instructive of an alternative approach to achieve resistance. Third, the R biotype was found to be resistant to multiple chemical families of PPO inhibitors, albeit at different levels (4), indicating that the ⌬G210 mutation confers resistance to all PPO inhibitors.…”

“…Although PPO-inhibitor-resistant plants have been generated through genetic engineering (14)(15)(16)(17)(18)(19)(20), A. tuberculatus populations have evolved resistance from the repeated use of these herbicides in agronomic production systems. The consequence of A. tuberculatus evolving resistance to PPO inhibitors, combined with its already widespread resistance to acetolactate synthase-inhibiting herbicides, is that the only remaining chemical option for its control following emergence in Glycine max (soybean) production systems is glyphosate, which requires the planting of glyphosate-resistant varieties (4).…”

Protoporphyrinogen‐IX‐oxidase Inhibitors

“…Research efforts continue to be devoted to the development of Protox inhibitor-resistant crops [121]. In 1999, Syngenta announced its discovery of a novel gene technology, under the trademark Acuron TM , that provides crops with tolerance to Protox inhibitors.…”

1(Heterocyclyl),2,4,5-Tetrasubstituted Benzenes as Protoporphyrinogen-IX Oxidase Inhibiting Herbicides

“…In recent years, the development of Protox inhibitor-resistant crops (Li and Nicholl, 2005;Vencill, 2011) began a new era for the use of Protox herbicides. Furthermore, weed shifts observed in genetically modified crops, caused by the development of weed resistance to the widely used glyphosate herbicide, will offer market opportunities for herbicides with other modes of action, such as Protox inhibiting herbicides.…”