International Survey of Herbicide-Resistant Weeds

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Thursday, November 21, 2024

ARROWLEAFED MONOCHORIA (Monochoria vaginalis) with GROUP B/2 resistance: (INHIBITION OF ACETOLACTATE SYNTHASE ) Inhibition of Acetolactate Synthase

MUTATION: PROLINE 197 to SERINE

Arrowleafed Monochoria (Monochoria vaginalis) is a monocot plant in the pontederiaceae family. A single amino acid substitution from Proline 197 to Serine has led to resistance to Inhibition of Acetolactate Synthase as indicated in the table below.		Arrowleafed Monochoria

Chemical Family	Example Herbicide	Resistance Level
Imidazolinones	Imazethapyr	Not Determined
Pyrimidinyl benzoates	Bispyribac-Na	Not Determined
Sulfonylureas	Chlorsulfuron	Resistant > 10 fold
Triazolopyrimidine - Type 1	Chloransulam-methyl	Not Determined
Triazolinones	Flucarbazone-Na	Not Determined

REFERENCES

Wang GuangXi ; Lin Ying ; Li Wei ; Ito, M. ; Itoh, K.. 2004. A mutation confers Monochoria vaginalis resistance to sulfonylureas that target acetolactate synthase. Pesticide Biochemistry and Physiology 80 : 43 - 46.

Acetolactate synthase (ALS) is the target enzyme for four distinct families of compounds: sulfonylureas (SUs), imidazolinones, triazolopyrimidine sulfonanilides, and pyrimidinyl oxybenzoates. We cloned and sequenced the fragments encoding ALS genes from biotypes of Monochoria vaginalis susceptible (S) and resistant (R) to SU-herbicides. The nucleotide sequences of the 39 bp Domain A region for R M. vaginalis biotype differed from that of the S biotype by a single nucleotide substitution at variable Pro codon of Domain A (CCT to TCT), predicting a Pro in the S but a Ser in the R biotype. No nucleotide differences between S and R M. vaginalis were observed in Domain D. We suggest that the amino acid substitution at Domain A region is responsible for resistance to SU-herbicides in M. vaginalis collected from Ushiku City, Ibaraki Prefecture, Japan..

Tanigaki, S. et al. . 2021. Gene expression shapes the patterns of parallel evolution of herbicide resistance in the agricultural weed Monochoria vaginalis. New Phytologist 232 : 928 - 940.

Summary

The evolution of herbicide resistance in weeds is an example of parallel evolution, throughwhich genes encoding herbicide target proteins are repeatedly represented as evolutionarytargets. The number of herbicide target-site genes differs among species, and little is knownregarding the effects of duplicate gene copies on the evolution of herbicide resistance.

We investigated the evolution of herbicide resistance in Monochoria vaginalis, which car-ries ﬁve copies of sulfonylurea target-site acetolactate synthase (ALS) genes. Suspected resis-tant populations collected across Japan were investigated for herbicide sensitivity and ALSgene sequences, followed by functional characterization and ALS gene expression analysis.

We identiﬁed over 60 resistant populations, all of which carried resistance-conferring aminoacid substitutions exclusively in MvALS1 or MvALS3. All MvALS4 alleles carried a loss-of-function mutation. Although the enzymatic properties of ALS encoded by these genes werenot markedly different, the expression of MvALS1 and MvALS3 was prominently higheramong all ALS genes.

The higher expression of MvALS1 and MvALS3 is the driving force of the biased represen-tation of genes during the evolution of herbicide resistance in M. vaginalis. Our ﬁndings high-light that gene expression is a key factor in creating evolutionary hotspots

This case was entered by Patrick Tranel Email: tranel@illinois.edu

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Cite this site as: Heap, I. The International Survey of Herbicide Resistant Weeds. Online. Internet. Thursday, November 21, 2024 . Available www.weedscience.org
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