Herbicides as Probes in Plant Biology

Abstract

Herbicides are small molecules that inhibit specific molecular target sites within plant biochemical pathways and/or physiological processes. Inhibition of these sites often has catastrophic consequences that are lethal to plants. The affinity of these compounds for their respective target sites makes them useful tools to study and dissect the intricacies of plant biochemical and physiological processes. For instance, elucidation of the photosynthetic electron transport chain was achieved in part by the use of herbicides, such as terbutryn and paraquat, which act on photosystem II and I, respectively, as physiological probes. Work stemming from the discovery of the binding site of PS II–inhibiting herbicides was ultimately awarded the Nobel Prize in 1988. Although not as prestigious as the seminal work on photosynthesis, our knowledge of many other plant processes expanded significantly through the ingenious use of inhibitors as molecular probes. Examples highlight the critical role played by herbicides in expanding our understanding of the fundamental aspects of the synthesis of porphyrins and the nonmevalonate pathway, the evolution of acetyl-coenzyme A carboxylase, cell wall physiology, the functions of microtubules and the cell cycle, the role of auxin and cyanide, the importance of subcellular protein targeting, and the development of selectable markers.

In Vivo 31P-Nuclear Magnetic Resonance Studies of Glyphosate Uptake, Vacuolar Sequestration, and Tonoplast Pump Activity in Glyphosate-Resistant Horseweed

“…Such behavior is consistent with active (ATP-dependent) membrane glyphosate transport. It is anticipated that in vivo NMR studies of whole-plant tissue will continue to play an important role in understanding herbicide action in weeds and genetically modified crops (Dayan et al, 2010;Grossmann et al, 2012;Délye et al, 2013).…”

Herbicides as Weed Control Agents: State of the Art: I. Weed Control Research and Safener Technology: The Path to Modern Agriculture

“…There are several excellent reviews and books on the MoAs of herbicides (Seitz et al, 2003;Liu et al, 2009;Dayan et al, 2010;Krämer at al, 2012) (Figs. 4 and 5).…”

“…These herbicides not only had a profound impact on weed control in agriculture but also played a major role in expanding the understanding of fundamental plant processes through their ingenious use as molecular probes (Dayan et al, 2010). Many academic groups in the United States as well as in Europe embarked on this path, either studying the MoAs of herbicides or using herbicides to study plant metabolism.…”

7-Keto-8-Aminopelagonic Acid Synthase as a Potential Herbicide Target

“…These are usually inhibitors of specific enzymes binding either at the active site of the enzyme or at some domain apart from the active site (Berg et al, 1999;Dayan et al 2009). Among the strategies to identify suitable targets, one strategy was to assume that if an enzyme in a pathway or process is a target, then others in the same pathway or process might be too.…”