In planta
analysis of the mode of action of cinmethylin and confirmation of fatty acyl‐
ACP
thioesterases (
FATs
) as pri
Maximillian Pollmeier, Aisha Gerhardt, Janneke Hendriks, Katharina Kaprocki, Alexandra Zimmermann, Sarina Ruehm, Martina Marnet, Maria Stroe, Jorge Alfredo Rojas Biava, Clara Hofmann, Michael Betz, Sascha Schlaefer, Philipp Ternes, Jens Lerchl, Selene Garcia‐Hernandez, Philipp Johnen Abstract
BACKGROUND
Resistances to most known herbicide modes of action have emerged in many weeds, highlighting the need for new modes and sites of action. Cinmethylin, a selective herbicide effective against multi‐resistant populations of Alopecurus myosuroides, Lolium rigidum, Lolium multiflorum and Apera spica‐venti in wheat, had been identified as an inhibitor of fatty acyl‐ACP thioesterases (FATs). Detailed analysis of its mode and site of action is important to understand efficacy, weed spectrum and resistance risk.
RESULTS
Our study presents a comprehensive characterization of cinmethylin utilizing an integrative approach combining biochemistry, cell biology, lipidomics and genetics using Arabidopsis thaliana and Alopecurus myosuroides . Our data show that the maintenance of FATA1 activity is sufficient to attenuate herbicidal effects on a macroscopic and microscopic level in Arabidopsis thaliana . We demonstrate that cinmethylin treatment leads to FAT‐dependent defects in cell division, cell elongation and cell integrity. Furthermore, we show that cinmethylin significantly reduced free fatty acid levels and led to changes in lipid homeostasis. Our data suggests that de novo lipid biosynthesis via the eukaryotic pathway is predominately linked to the mode of action of cinmethylin. By contrast, plastid lipid biosynthesis via the prokaryotic pathway plays only a minor role in the herbicidal effect.
CONCLUSION
Based on the presented data, we confirm that FATs, as the entry point into the eukaryotic pathway of lipid biosynthesis in planta, are the primary site of action of cinmethylin and that cinmethylin's primary mode of action is based on an impaired cell division, elongation and membrane integrity. © 2026 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.