Glyphosate-resistant goosegrass. Identification of a mutation in the target enzyme 5-enolpyruvylshikimate-3-phosphate synthase.
The spontaneous occurrence of resistance to the herbicide glyphosate in weed species has been an extremely infrequent event, despite over 20 years of extensive use. Recently, a glyphosate-resistant biotype of goosegrass (Eleusine indica) was identified in Malaysia exhibiting an LD(50) value approximately 2- to 4-fold greater than the sensitive biotype collected from the same region. A comparison of the inhibition of 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) activity by glyphosate in extracts prepared from the resistant (R) and sensitive (S) biotypes revealed an approximately 5-fold higher IC(50)(glyphosate) for the (R) biotype. Sequence comparisons of the predicted EPSPS mature protein coding regions from both biotypes revealed four single-nucleotide differences, two of which result in amino acid changes. One of these changes, a proline to serine substitution at position 106 in the (R) biotype, corresponds to a substitution previously identified in a glyphosate-insensitive EPSPS enzyme from Salmonella typhimurium. Kinetic data generated for the recombinant enzymes suggests that the second substitution identified in the (R) EPSPS does not contribute significantly to its reduced glyphosate sensitivity. Escherichia coli aroA- (EPSPS deficient) strains expressing the mature EPSPS enzyme from the (R) biotype exhibited an approximately 3-fold increase in glyphosate tolerance relative to strains expressing the mature EPSPS from the (S) biotype. These results provide the first evidence for an altered EPSPS enzyme as an underlying component of evolved glyphosate resistance in any plant species.
Baerson
Scott R
SR
Monsanto Company, 700 Chesterfield Parkway North, St. Louis, Missouri 63198, USA. sbaerson@olemiss.edu
Rodriguez
Damian J
DJ
Tran
Minhtien
M
Feng
Yongmei
Y
Biest
Nancy A
NA
Dill
Gerald M
GM
D051229:3-Phosphoshikimate 1-Carboxyvinyltransferase; D019883:Alkyl and Aryl Transferases / Q000235:genetics* / Q000378:metabolism; D000595:Amino Acid Sequence; D001483:Base Sequence; D018076:DNA, Complementary / Q000737:chemistry / Q000235:genetics; D004351:Drug Resistance / Q000235:genetics; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics / Q000254:growth & development; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D005998:Glycine / Q000031:analogs & derivatives* / Q000494:pharmacology*; D006540:Herbicides / Q000494:pharmacology*; D020128:Inhibitory Concentration 50; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D007700:Kinetics; D008969:Molecular Sequence Data; D009154:Mutation; D006109:Poaceae / Q000187:drug effects / Q000201:enzymology / Q000235:genetics*; D017422:Sequence Analysis, DNA; D000097797:Glyphosate
D051229:3-Phosphoshikimate 1-Carboxyvinyltransferase; D019883:Alkyl and Aryl Transferases; D018076:DNA, Complementary; D005998:Glycine; D006540:Herbicides; D007527:Isoenzymes; D000097797:Glyphosate