Dataset Information

Target-site and non-target-site based resistance to the herbicide tribenuron-methyl in flixweed (Descurainia sophia L.).

ABSTRACT: Flixweed (Descurainia sophia L.) is a troublesome and widespread broadleaf weed in winter fields in China, and has evolved high level resistance to acetolactate synthase (ALS)-inhibiting sulfonylurea herbicide tribenuron-methyl.We identified a resistant flixweed population (N11) exhibiting 116.3-fold resistance to tribenuron-methyl relative to the susceptible population (SD8). Target-site ALS gene mutation Pro-197-Thr was identified in resistant plants. Moreover, the resistance can be reversed to 28.7-fold by the cytochrome P450 inhibitor malathion. The RNA-Sequencing was employed to identify candidate genes involved in non-target-site metabolic resistance in this population. Total 26 differentially expressed contigs were identified and eight of them (four P450s, one ABC transporter, three glycosyltransferase) verified by qRT-PCR. Consistent over-expression of the two contigs homology to CYP96A13 and ABCC1 transporter, respectively, were further qRT-PCR validated using additional plants from the resistant and susceptible populations.Tribenuron-methyl resistance in flixweed is controlled by target-site ALS mutation and non-target-site based mechanisms. Two genes, CYP96A13 and ABCC1 transporter, could play an important role in metabolic resistance to tribenuron-methyl in the resistant flixweed population and justify further functional studies.

SUBMITTER: Yang Q

PROVIDER: S-EPMC4974779 | biostudies-literature | 2016 Aug

REPOSITORIES: biostudies-literature

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Target-site and non-target-site based resistance to the herbicide tribenuron-methyl in flixweed (Descurainia sophia L.).

Yang Qian Q Deng Wei W Li Xuefeng X Yu Qin Q Bai Lianyang L Zheng Mingqi M

BMC genomics 20160805

<h4>Background</h4>Flixweed (Descurainia sophia L.) is a troublesome and widespread broadleaf weed in winter fields in China, and has evolved high level resistance to acetolactate synthase (ALS)-inhibiting sulfonylurea herbicide tribenuron-methyl.<h4>Results</h4>We identified a resistant flixweed population (N11) exhibiting 116.3-fold resistance to tribenuron-methyl relative to the susceptible population (SD8). Target-site ALS gene mutation Pro-197-Thr was identified in resistant plants. Moreove ...[more]

PMID: 27495977

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Project description:BackgroundWater chickweed (Myosoton aquaticum (L.)) is a dicot broadleaf weed that is widespread in winter fields in China, and has evolved serious resistance to acetolactate synthase (ALS) inhibiting herbicides.ResultsWe identified a M. aquaticum population exhibiting moderate (6.15-fold) resistance to tribenuron-methyl (TM). Target-site ALS gene sequencing revealed no known resistance mutations in these plants, and the in vitro ALS activity assays showed no differences in enzyme sensitivity between susceptible and resistant populations; however, resistance was reversed by pretreatment with the cytochrome P450 (CYP) monooxygenase inhibitor malathion. An RNA sequencing transcriptome analysis was performed to identify candidate genes involved in metabolic resistance, and the unigenes obtained by de novo transcriptome assembly were annotated across seven databases. In total, 34 differentially expressed genes selected by digital gene expression analysis were validated by quantitative real-time (qRT)-PCR. Ten consistently overexpressed contigs, including four for CYP, four for ATP-binding cassette (ABC) transporter, and two for peroxidase were further validated by qRT-PCR using additional plants from resistant and susceptible populations. Three CYP genes (with homology to CYP734A1, CYP76C1, and CYP86B1) and one ABC transporter gene (with homology to ABCC10) were highly expressed in all resistant plants.ConclusionThe mechanism of TM resistance in M. aquaticum is controlled by NTSR rather than TSR. Four genes, CYP734A1, CYP76C1, CYP86B1, and ABCC10 could play essential role in metabolic resistance to TM and justify further functional studies. To our knowledge, this is the first large-scale transcriptome analysis of genes associated with NTSR in M. aquaticum using the Illumina platform. Our data provide resource for M. aquaticum biology, and will facilitate the study of herbicide resistance mechanism at the molecular level in this species as well as in other weeds.

Project description:The evolution of resistance to herbicides is a classic example of rapid contemporary adaptation in the face of a novel environmental stress. Evolutionary theory predicts that selection for resistance will be accompanied by fitness trade-offs in environments where the stress is absent. Alopecurus myosuroides, an autumn-germinating grass weed of cereal crops in North-West Europe, has evolved resistance to seven herbicide modes-of-action, making this an ideal species to examine the presence and magnitudes of such fitness costs. Here, we use two contrasting A. myosuroides phenotypes derived from a common genetic background, one with enhanced metabolism resistance to a commercial formulation of the sulfonylurea (ALS) actives mesosulfuron and iodosulfuron, and the other with susceptibility to these actives (S). Comparisons of plant establishment, growth, and reproductive potential were made under conditions of intraspecific competition, interspecific competition with wheat, and over a gradient of nitrogen deprivation. Herbicide dose response assays confirmed that the two lines had contrasting resistance phenotypes, with a 20-fold difference in resistance between them. Pleiotropic effects of resistance were observed during plant development, with R plants having a greater intraspecific competitive effect and longer tiller lengths than S plants during vegetative growth, but with S plants allocating proportionally more biomass to reproductive tissues during flowering. Direct evidence of a reproductive cost of resistance was evident in the nitrogen deprivation experiment with R plants producing 27% fewer seed heads per plant, and a corresponding 23% reduction in total seed head length. However, these direct effects of resistance on fecundity were not consistent across experiments. Our results demonstrate that a resistance phenotype based on enhanced herbicide metabolism has pleiotropic impacts on plant growth, development and resource partitioning but does not support the hypothesis that resistance is associated with a consistent reproductive fitness cost in this species. Given the continued difficulties associated with unequivocally detecting costs of herbicide resistance, we advocate future studies that adopt classical evolutionary quantitative genetics approaches to determine genetic correlations between resistance and fitness-related plant life history traits.

Project description:Repeated application of pesticides disturbs microbial communities and cause dysfunctions on soil biological processes. Granstar® 75 DF is one of the most used sulfonylurea herbicides on cereal crops; it contains 75% of tribenuron-methyl. Assessing the changes on soil microbiota, particularly on the most abundant bacterial groups, will be a useful approach to determine the impact of Granstar® herbicide. For this purpose, we analyzed Actinobacteria, which are known for their diversity, abundance, and aptitude to resist to xenobiotic substances. Using a selective medium for Actinobacteria, 42 strains were isolated from both untreated and Granstar® treated soils. The number of isolates recovered from the treated agricultural soil was fewer than that isolated from the corresponding untreated soil, suggesting a negative effect of Granstar® herbicide on Actinobacteria community. Even so, the number of strains isolated from untreated and treated forest soil was quite similar. Among the isolates, resistant strains, tolerating high doses of Granstar® ranging from 0.3 to 0.6% (v/v), were obtained. The two most resistant strains (SRK12 and SRK17) were isolated from treated soils showing the importance of prior exposure to herbicides for bacterial adaptation. SRK12 and SRK17 strains showed different morphological features. The phylogenetic analysis, based on 16S rRNA gene sequencing, clustered the SRK12 strain with four Streptomyces type strains (S. vinaceusdrappus, S. mutabilis, S. ghanaensis and S. enissocaesilis), while SRK17 strain was closely related to Streptomyces africanus. Both strains were unable to grow on tribenuron methyl as unique source of carbon, despite its advanced dissipation. On the other hand, when glucose was added to tribenuron methyl, the bacterial development was evident with even an improvement of the tribenuron methyl degradation. In all cases, as tribenuron methyl disappeared, two compounds were detected with increased concentrations. These by-products appeared to be persistent and were not degraded either chemically or by the studied strains. Based on these observations, we suggested that bacterial activity on carbon substrates could be directly involved in the partial breakdown of tribenuron methyl, by generating the required acidity for the first step of the hydrolysis. Such a process would be interesting to consider in bioremediation of neutral and alkaline tribenuron methyl-polluted soils.

Project description:Non-target site resistance (NTSR) to herbicides in black-grass (Alopecurus myosuroides) results in enhanced tolerance to multiple chemistries and is widespread in Northern Europe. To help define the underpinning mechanisms of resistance, global transcriptome and biochemical analysis have been used to phenotype three NTSR black-grass populations. These comprised NTSR1 black-grass from the classic Peldon field population, which shows broad-ranging resistance to post-emergence herbicides; NTSR2 derived from herbicide-sensitive (HS) plants repeatedly selected for tolerance to pendimethalin; and NTSR3 selected from HS plants for resistance to fenoxaprop-P-ethyl. NTSR in weeds is commonly associated with enhanced herbicide metabolism catalyzed by glutathione transferases (GSTs) and cytochromes P450 (CYPs). As such, the NTSR populations were assessed for their ability to detoxify chlorotoluron, which is detoxified by CYPs and fenoxaprop-P-ethyl, which is acted on by GSTs. As compared with HS plants, enhanced metabolism toward both herbicides was determined in the NTSR1 and NTSR2 populations. In contrast, the NTSR3 plants showed no increased detoxification capacity, demonstrating that resistance in this population was not due to enhanced metabolism. All resistant populations showed increased levels of AmGSTF1, a protein functionally linked to NTSR and enhanced herbicide metabolism. Enhanced AmGSTF1 was associated with increased levels of the associated transcripts in the NTSR1 and NTSR2 plants, but not in NTSR3, suggestive of both pre- and post-transcriptional regulation. The related HS, NTSR2, and NTSR3 plants were subject to global transcriptome sequencing and weighted gene co-expression network analysis to identify modules of genes with coupled regulatory functions. In the NTSR2 plants, modules linked to detoxification were identified, with many similarities to the transcriptome of NTSR1 black-grass. Critical detoxification genes included members of the CYP81A family and tau and phi class GSTs. The NTSR2 transcriptome also showed network similarities to other (a)biotic stresses of plants and multidrug resistance in humans. In contrast, completely different gene networks were activated in the NTSR3 plants, showing similarity to the responses to cold, osmotic shock and fungal infection determined in cereals. Our results demonstrate that NTSR in black-grass can arise from at least two distinct mechanisms, each involving complex changes in gene regulatory networks.

Dataset Information

Target-site and non-target-site based resistance to the herbicide tribenuron-methyl in flixweed (Descurainia sophia L.).

Publications

Target-site and non-target-site based resistance to the herbicide tribenuron-methyl in flixweed (Descurainia sophia L.).

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