Binding of the respiratory chain inhibitor ametoctradin to the mitochondrial bc1 complex.
BACKGROUND
Ametoctradin is an agricultural fungicide that inhibits the mitochondrial bc1 complex of oomycetes. The bc1 complex has two quinone binding sites that can be addressed by inhibitors. Depending on their binding sites and binding modes, the inhibitors show different degrees of cross-resistance that need to be considered when designing spray programmes for agricultural fungicides. The binding site of ametoctradin was unknown.


RESULTS
Cross-resistance analyses, the reduction of isolated Pythium sp. bc1 complex in the presence of different inhibitors and molecular modelling studies were used to analyse the binding site and binding mode of ametoctradin. All three approaches provide data supporting the argument that ametoctradin binds to the Pythium bc1 complex similarly to stigmatellin.


CONCLUSIONS
The binding mode of ametoctradin differs from other agricultural fungicides such as cyazofamid and the strobilurins. This explains the lack of cross-resistance with strobilurins and related inhibitors, where resistance is mainly caused by G143A amino acid exchange. Accordingly, mixtures or alternating applications of these fungicides and ametoctradin can help to minimise the risk of the emergence of new resistant isolates.
BASF SE, Crop Protection, Limburgerhof, Germany.
Marcus
M
Fehr
BASF SE, Biological and Effect Systems Research, Ludwigshafen, Germany.
Antje
A
Wolf
BASF SE, Crop Protection, Limburgerhof, Germany.
Gerd
G
Stammler
D001203:Ascomycota / Q000187:drug effects*; D001665:Binding Sites / Q000187:drug effects; D004579:Electron Transport / Q000187:drug effects; D014450:Electron Transport Complex III / Q000037:antagonists & inhibitors*; D005659:Fungicides, Industrial / Q000494:pharmacology*; D008958:Models, Molecular; D009868:Oomycetes / Q000187:drug effects*; D011743:Pyrimidines / Q000494:pharmacology*; D011809:Quinones / Q000737:chemistry; D014230:Triazoles / Q000494:pharmacology*
D005659:Fungicides, Industrial; D011743:Pyrimidines; D011809:Quinones; D014230:Triazoles; D014450:Electron Transport Complex III; C000601857:ametoctradin
Initium; ametoctradin; bc1 complex; complex III; respiration inhibitor; stigmatellin