Auxinic herbicides, mechanisms of action, and weed resistance: A look into recent plant science advances

Abstract

Auxin governs dynamic cellular processes involved at several stages of plant growth and development. In this review, we discuss the mechanisms employed by auxin in light of recent scientific advances, with a focus on synthetic auxins as herbicides and synthetic auxin resistance mechanisms. Two auxin receptors were reported. The plasma membrane receptor Recently, another ubiquitination pathway which is described as a new auxin signaling route is the F-box protein S-Phase Kinase-Associated Protein 2A (SKP2A). It is active in cell division regulation and there is evidence that auxin herbicides can deregulate the SKP2A pathway, which leads to severe defects in plant development. In this discussion, we propose that SFC SKP2A auxin binding site alteration could be a new auxinic herbicide resistance mechanism, a concept which may contribute to the current progress in plant biology in its quest to clarify the many questions that still surround auxin herbicide mechanisms of action and the mechanisms of weed resistance.

Spectrum of Weed Control With 2,4-D and Dicamba Herbicides Associated to Glyphosate or Not

“…The effects of increased ethylene concentrations in plants are leaf epinasty, tissue swelling and plant senescence, as well as being the trigger for an increase in the production of abscisic acid (ABA). Increased levels of this hormone promote stomata closing, which limits transpiration and carbon assimilation, and the "super production" of reactive oxygen species (Grossman, 2000(Grossman, , 2010Christoffoleti et al, 2015). …”

First report: spotted knapweed (Centaurea stoebe) resistance to auxinic herbicides

“…Unlike auxinic resistance in wild mustard (Hall and Romano 1995), resistant knapweed plants showed normal growth; however, following herbicide treatment, plants showed some epinasty without tissue necrosis. This may indicate a resistance mechanism that interferes with the complex between TIR1, AFBs or Aux/IAA (Christoffoleti et al 2015). This is the first resistant spotted knapweed population reported and the first case of a weed reporting a high level of clopyralid resistance.…”

“…Auxins regulate gene expression of auxin responsive factors (ARFs) through the promotion of degradation of Aux/IAA (auxin/indole acetic acid) transcription factors via binding to the complex of the transport inhibitor response (TIR)/auxin-signaling F-box (AFB), which are protein components of the Skip, Cullin, F-Box (SCF) (Christoffoleti et al 2015;Mithila et al 2011). Different types of auxinic herbicides exhibit different binding affinity to the TIR complex.…”

“…Different types of auxinic herbicides exhibit different binding affinity to the TIR complex. Uncontrolled gene expression of ARFs leads to increased synthesis of plant hormones (abscissic acid (ABA) and ethylene), resulting in excessive plant growth, epinasty, and cell death in sensitive plants (Christoffoleti et al 2015).…”

Reduced translocation in 2,4‐D‐resistant oriental mustard populations (Sisymbrium orientale L.) from Australia

“…12 Even though the first case of resistance to 2,4-D was reported in wild carrot (Daucus carota) in 1957, 13 only 34 cases of resistance to auxinic herbicides have been identified worldwide, 14 and the mechanisms of resistance in many cases remain unknown. 15 Several putative target-site resistance (TSR) and non-target-site resistance (NTSR) mechanisms have been reported to confer resistance to this herbicide group. 2 However, due to its complex mode of action, the evolution of resistance to auxinic herbicides in weeds is considered to be more likely associated with NTSR.…”