About this Research Topic
NTSR affects different enzyme families of plant catabolic routes in plant primary metabolism; the main targets are the cytochrome P450 enzymatic complex (phase I) and the glutathione-S-transferase and glycosyltransferase enzyme families (phase II). The potential responses coordinated by these enzymes are yet to be unravelled. New research suggests that the selection pressure exerted by one herbicide on one specific gene could simultaneously select the differential expression of other resistance-conferring genes. Although the proteins responsible for inactivating or sequestering different herbicides may differ, the mechanism of herbicide metabolism that confers cross-resistance might be common. Recent research has discovered another class of enzymes, aldo-keto reductases, which are involved in the metabolism of glyphosate and confer glyphosate resistance. This evidence should stimulate a search for other glyphosate-metabolizing enzymes.
Other enzymes, such as peroxidases, are involved in different mechanisms leading to herbicide resistance. Peroxidases protect plants from herbicide damage and seem to be responsible for NTSR and conferring cross-resistance. Similarly, ABC transporters (phase III) are linked to reduced transport/sequestration of some herbicides. These transporters have several known substrates, and this raises the possibility that they may be involved in translocating different herbicides. An additional question that naturally arises is what resistant plants do with herbicides: are they inactivated in planta, sequestered or secreted? NTSR mechanisms can act alongside TSR mechanisms building up the resistance response. Combined NTSR and TSR mechanisms, such as increased metabolic activity coupled with root exudation, could enable plants to promote herbicide elimination. Other hypothesized modes of action contributing to herbicide resistance mechanisms include epigenetic control and circadian control.
The above-mentioned questions point to several potential mechanisms of herbicide resistance that need to be addressed in future research towards safeguarding food production together with judicious use of herbicides. This Research Topic aims to collect:
• Latest research identifying and characterizing the enzymes and genes involved in enhanced metabolism (increased herbicide metabolism)
• Studies unravelling new NTSR mechanisms that could also confer cross and multiple herbicide resistance
• Studies reporting new cases of multiple herbicide resistance weeds worldwide together with the mechanistic insights behind them.
Keywords: Non-target site resistance, Herbicide-resistant weeds, Metabolism, Multiple resistant weeds, Cross resistance
Important Note: All contributions to this Research Topic must be within the scope of the section and journal to which they are submitted, as defined in their mission statements. Frontiers reserves the right to guide an out-of-scope manuscript to a more suitable section or journal at any stage of peer review.