Targenomix GmbH, Potsdam, Germany.
Crop Science Division, Structural Biology, Bayer AG, Monheim am Rhein, Germany.
Pest Manag Sci. 2020 Oct;76(10):3377-3388. doi: 10.1002/ps.5781. Epub 2020 Feb 27.
Aclonifen is a unique diphenyl ether herbicide. Despite its structural similarities to known inhibitors of the protoporphyrinogen oxidase (e.g. acifluorfen, bifenox or oxadiazon), which result in leaf necrosis, aclonifen causes a different phenotype that is described as bleaching. This also is reflected by the Herbicide Resistance Action Committee (HRAC) classification that categorizes aclonifen as an inhibitor of pigment biosynthesis with an unknown target.
A comprehensive Arabidopsis thaliana RNAseq dataset comprising 49 different inhibitor treatments and covering 40 known target pathways was used to predict the aclonifen mode of action (MoA) by a random forest classifier. The classifier predicts for aclonifen a MoA within the carotenoid biosynthesis pathway similar to the reference compound norflurazon that inhibits the phytoene desaturase. Upon aclonifen treatment, the phytoene desaturation reaction is disturbed, resulting in a characteristic phytoene accumulation in vivo. However, direct enzyme inhibition by the herbicide was excluded for known herbicidal targets such as phytoene desaturase, 4-hydroxyphenylpyruvate dioxygenase and homogentisate solanesyltransferase. Eventually, the solanesyl diphosphate synthase (SPS), providing one of the two homogentisate solanesyltransferase substrate molecules, could be identified as the molecular target of aclonifen. Inhibition was confirmed using biochemical activity assays for the A. thaliana SPSs 1 and 2. Furthermore, a Chlamydomonas reinhardtii homolog was used for co-crystallization of the enzyme-inhibitor complex, showing that one inhibitor molecule binds at the interface between two protein monomers.
Solanesyl diphosphate synthase was identified as the target of aclonifen, representing a novel mode of action for herbicides. © 2020 Society of Chemical Industry.
Aclonifen 是一种独特的二苯醚类除草剂。尽管它的结构与已知的原卟啉原氧化酶抑制剂（如 acifluorfen、bifenox 或 oxadiazon）相似，导致叶片坏死，但 aclonifen 会导致不同的表型，被描述为漂白。这也反映在除草剂抗性行动委员会（HRAC）的分类中，将 aclonifen 归类为一种未知靶标的色素生物合成抑制剂。
使用包含 49 种不同抑制剂处理和涵盖 40 种已知靶标途径的综合拟南芥 RNAseq 数据集，通过随机森林分类器预测 aclonifen 的作用模式（MoA）。该分类器预测 aclonifen 的 MoA 位于类胡萝卜素生物合成途径内，类似于抑制脱植烯酶的参考化合物 norflurazon。在 aclonifen 处理后，脱植烯反应受到干扰，导致体内特征性的类胡萝卜素积累。然而，对于已知的除草剂靶标，如脱植烯酶、4-羟苯基丙酮酸双加氧酶和 homogentisate solanesyltransferase，除草剂直接抑制酶的作用被排除在外。最终，可以确定 solanesyl diphosphate synthase（SPS）是 aclonifen 的分子靶标，它提供了 homogentisate solanesyltransferase 的两个底物分子之一。使用生化活性测定法对拟南芥 SPSs 1 和 2 进行了抑制验证。此外，还使用 Chlamydomonas reinhardtii 同源物进行了酶-抑制剂复合物的共结晶，表明一个抑制剂分子结合在两个蛋白质单体之间的界面上。
Solanesyl diphosphate synthase 被鉴定为 aclonifen 的靶标，代表了除草剂的一种新作用模式。© 2020 化学工业协会。
