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Chemically induced herbicide tolerance in rice by the safener metcamifen is associated with a phased stress response.

ABSTRACT: The closely related sulphonamide safeners, metcamifen and cyprosulfamide, were tested for their ability to protect rice from clodinafop-propargyl, a herbicide normally used in wheat. While demonstrating that both compounds were equally bioavailable in planta, only metcamifen prevented clodinafop from damaging seedlings, and this was associated with the enhanced detoxification of the herbicide. Transcriptome studies in rice cultures demonstrated that whereas cyprosulfamide had a negligible effect on gene expression over a 4 h exposure, metcamifen perturbed the abundance of 590 transcripts. Changes in gene expression with metcamifen could be divided into three phases, corresponding to inductions occurring over 30 min, 1.5 h and 4 h. The first phase of gene induction was dominated by transcription factors and proteins of unknown function, the second by genes involved in herbicide detoxification, while the third was linked to cellular homeostasis. Analysis of the inducible genes suggested that safening elicited similar gene families to those associated with specific biotic and abiotic stresses, notably those elicited by abscisic acid, salicylic acid, and methyl jasmonate. Subsequent experiments with safener biomarker genes induced in phase 1 and 2 in rice cell cultures provided further evidence of similarities in signalling processes elicited by metcamifen and salicylic acid.

SUBMITTER: Brazier-Hicks M

PROVIDER: S-EPMC6913702 | biostudies-literature | 2020 Jan

REPOSITORIES: biostudies-literature

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Chemically induced herbicide tolerance in rice by the safener metcamifen is associated with a phased stress response.

Brazier-Hicks Melissa M Howell Anushka A Cohn Jonathan J Hawkes Tim T Hall Gavin G Mcindoe Eddie E Edwards Robert R

Journal of experimental botany 20200101 1

The closely related sulphonamide safeners, metcamifen and cyprosulfamide, were tested for their ability to protect rice from clodinafop-propargyl, a herbicide normally used in wheat. While demonstrating that both compounds were equally bioavailable in planta, only metcamifen prevented clodinafop from damaging seedlings, and this was associated with the enhanced detoxification of the herbicide. Transcriptome studies in rice cultures demonstrated that whereas cyprosulfamide had a negligible effect ...[more]

PMID: 31565749

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Project description:BACKGROUND AND AIMS: Sulfonylurea (SU) herbicides are used extensively in cereal-livestock farming zones as effective and cheap herbicides with useful levels of residual activity. These residues can persist beyond the cropping year, severely affecting legumes in general, and annual medics in particular, resulting in reduced dry matter production, lower seed yields and decreased nitrogen fixation. A strand medic cultivar, Medicago littoralis 'Angel', has been developed via chemical mutagenesis with tolerance to SU soil residues. Identifying the molecular basis of the observed tolerance was the aim of this study. METHODS: Two F(2) populations were generated from crosses between 'Angel' and varieties of intolerant M. truncatula, the male-sterile mutant tap and the cultivar 'Caliph'. Genetic mapping with SSR (single sequence repeat) and gene-based markers allowed identification of the trait-defining gene. Quantitative gene expression studies showed the activity of the respective alleles. KEY RESULTS: Segregation ratios indicated the control of SU-herbicide tolerance by a single dominant gene. SU herbicides inhibit the biosynthesis of the branched-chain amino acids by targeting the acetolactate synthase enzyme, allowing the choice of a mapping approach using acetolactate synthase (ALS) gene homologues as candidates. SSR-marker analysis suggested the ALS-gene homologue on chromosome 3 in M. truncatula. The ALS-gene sequences from 'Angel' and intolerant genotypes were sequenced. In 'Angel', a single point mutation from C to T translating into an amino acid change from proline to leucine was identified. The polymorphism was used to develop a diagnostic marker for the tolerance trait. Expression of the mutant ALS allele was confirmed by quantitative RT-PCR and showed no differences at various seedling stages and treatments to the corresponding wild-type allele. CONCLUSIONS: The identification of the trait-defining gene and the development of a diagnostic marker enable efficient introgression of this economically important trait in annual medic improvement programs.

Project description:The use of herbicide safeners can significantly alleviate herbicide injury to protect crop plants and expand the application scope of the existing herbicides in the field. Sanshools, which are well known as spices, are N-alkyl substituted compounds extracted from the Zanthoxylum species and have several essential physiological and pharmacological functions. Sanshools display excellent safener activity for the herbicide metolachlor in rice seedlings. However, the high cost of sanshools extraction and difficulties in the synthesis of their complicated chemical structures limit their utilization in agricultural fields. Thus, the present study designed and synthesized various N-alkyl amide derivatives via the scaffold-hopping strategy to solve the challenge of complicated structures and find novel potential safeners for the herbicide metolachlor. In total, 33 N-alkyl amide derivatives (2a-k, 3a-k, and 4a-k) were synthesized using amines and saturated and unsaturated fatty acids as starting materials through acylation and condensation. The identity of all the target compounds was well confirmed by 1H-NMR, 13C-NMR, and high-resolution mass spectrometry (HRMS). The primary evaluation of safener activities for the compounds by the agar method indicated that most of the target compounds could protect rice seedlings from injury caused by metolachlor. Notably, compounds 2k and 4k displayed excellent herbicide safener activities on plant height and demonstrated relatively similar activities to the commercialized compound dichlormid. Moreover, we showed that compounds 2k and 4k had higher glutathione S-transferase (GST), superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), and polyphenol oxidase (PPO) activities in rice seedlings, compared to the metolachlor treatment. In particular, 2k and 4k are safer for aquatic organisms than dichlormid. Results from the current work exhibit that compounds 2k and 4k have excellent crop safener activities toward rice and can, thus, be promising candidates for further structural optimization in rice protection.

Project description:The safener fenclorim (4,6-dichloro-2-phenylpyrimidine) increases tolerance to chloroacetanilide herbicides in rice by enhancing the expression of detoxifying glutathione S-transferases (GSTs). Fenclorim also enhances GSTs in Arabidopsis thaliana, and while investigating the functional significance of this induction in suspension cultures, we determined that these enzymes glutathionylated the safener. The resulting S-(fenclorim)-glutathione conjugate was sequentially processed to S-(fenclorim)-gamma-glutamyl-cysteine and S-(fenclorim)-cysteine (FC), the latter accumulating in both the cells and the medium. FC was then either catabolized to 4-chloro-6-(methylthio)-phenylpyrimidine (CMTP) or N-acylated with malonic acid. These cysteine derivatives had distinct fates, with the enzymes responsible for their formation being induced by fenclorim and FC. Fenclorim-N-malonylcysteine was formed from FC by the action of a malonyl-CoA-dependent N-malonyltransferase. A small proportion of the fenclorim-N-malonylcysteine then underwent decarboxylation to yield a putative S-fenclorim-N-acetylcysteine intermediate, which underwent a second round of GST-mediated S-glutathionylation and subsequent proteolytic processing. The formation of CMTP was catalyzed by the concerted action of a cysteine conjugate beta-lyase and an S-methyltransferase, with the two activities being coordinately regulated. Although the fenclorim conjugates tested showed little GST-inducing activity in Arabidopsis, the formation of CMTP resulted in metabolic reactivation, with the product showing good enhancing activity. In addition, CMTP induced GSTs and herbicide-safening activity in rice. The bioactivated CMTP was in turn glutathione-conjugated and processed to a malonyl cysteine derivative. These results reveal the surprisingly complex set of competing catabolic reactions acting on xenobiotics entering the S-glutathionylation pathway in plants, which can result in both detoxification and bioactivation.

Dataset Information

Chemically induced herbicide tolerance in rice by the safener metcamifen is associated with a phased stress response.

Publications

Chemically induced herbicide tolerance in rice by the safener metcamifen is associated with a phased stress response.

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