How protoporphyrinogen IX oxidase inhibitors and transgenesis contribute to elucidate plant tetrapyrrole pathway

Abstract

Several families of herbicides, especially diphenyl ether (DPE) and pyrimidinedione, target the plant tetrapyrrole biosynthesis pathways and in particular one key enzyme, protoporphyrinogen IX oxidase (PPO). When plants are treated with DPE or pyrimidinedione, an accumulation of protoporphyrin IX, the first photosensitizer of this pathway, is observed in cytosol where it becomes very deleterious under light. Indeed these herbicides trigger plant death in two distinct ways: (i) inhibition of chlorophylls and heme syntheses and (ii) a huge accumulation of protoporphyrin IX in cytosol. Recently, a strategy based on plant transgenesis that induces deregulation of the tetrapyrrole pathway by up- or down-regulation of genes encoding enzymes, such as glutamyl-[Formula: see text]RNA reductase, porphobilinogen deaminase and PPO, has been developed. Against all expectations, only transgenic crops overexpressing PPO showed resistance to DPE and pyrimidinedione. This herbicide resistance of transgenic crops leads to the hypothesis that the overall consumption of herbicides will be reduced as previously reported for glyphosate-resistant transgenic crops. In this review, after a rapid presentation of plant tetrapyrrole biosynthesis, we show how only PPO enzyme can be the target of DPE and how transgenic crops can be further resistant not only to herbicide but also to abiotic stress such as drought or chilling. Keeping in mind that this approach is mostly prohibited in Europe, we attempt to discuss it to interest the scientific community, from plant physiologists to chemists, who work on the interface of photosensitizer optimization and agriculture.

The inhibition of photosynthesis of Angelica dahurica caused by early bolting

“…Previous study indicated that the increasing accumulation of saturated fatty acids in the early senescence stage could improve the sensitivity to ethylene and promote the owering of Petunia hybrida [29]. And long-chain fatty acids were involved in the transport of polar auxin in A. thaliana [21]. In addition, studies on membrane lipids of photosynthetic organs in leaves showed that the increase of unsaturated fatty acid ratio helps to protect plant PSII damage under stress, maintain the stability of thylakoid membrane, and improve the photosynthetic heat resistance of plants.…”

“…However, the transcription level of AdhemH was up-regulated in BT plants. The hemH catalyzes the chelation of protoporphyrin IX with Fe to form heme, which essentially competes with chlorophyll synthesis pathway for protoporphyrin IX [21]. In cucumber seedlings under salt stress, the transcription level of protoporphyrin iron chelatase increased, while the transcription level of several genes in chlorophyll synthesis pathway was down-regulated.…”

Carboxylic Acid Derivatives in Herbicide Development

“…PPO-inhibiting herbicides target the biosynthesis of critical pigments in living plants. They can inactivate the PPO enzyme via competing for the binding site between the protogen and PPO enzyme . The inhibition of the PPO enzyme leads to a block in the biosynthesis of proto and causes the accumulation and leakage of protogen into the cytoplasm.…”

Photodynamic inactivation of Botrytis cinerea by an anionic porphyrin: an alternative pest management of grapevine

“…To fight off plant competitors and pathogens, new approaches are necessary for safe practices in agriculture such as genetically modified plants, genetic improvements, as well as organic and integrated agriculture 5 , 6 . The photodynamic treatment is a general and new concept with a large spectrum of applications for animal and plant cells, plant and animal pathogens, as well as microorganisms 7 – 18 . Thus, photodynamic treatment could represent an innovative and powerful strategy to fight off plant competitors and pathogens in future agricultural practices 17 .…”