What Is New for the Mechanisms of Plant Resistance to Paraquat After Decades of Research?

Abstract

Paraquat is one of the most widely used nonselective herbicides globally. Although the emergence of weed resistance to paraquat has progressed relatively slowly since the first reported case in Japan in 1980, it has been steadily increasing. Resistance in weedy plants is predominantly associated with non-target-site resistance (NTSR), particularly via reduced uptake and translocation to target sites (i.e., chloroplasts) and/or enhanced sequestration; increased antioxidant capacity is also a common mechanism by which plants cope with various stresses, including reactive oxygen species (ROS). However, direct evidence for paraquat transport mediated by membrane transporters in weeds has not been established. Over the past decade, research, especially in model plants such as Arabidopsis thaliana, has advanced our understanding of the mechanisms underlying plant resistance to paraquat. This brief review summarized recent studies on paraquat resistance, with a particular focus on uptake, translocation, and sequestration mechanisms. For instance, three L-amino acid transporter (LAT) proteins (LAT1/3/4) and one (PDR11) belonging to the PDR (pleiotropic drug resistance) subfamily within the ABC (ATP-binding cassette) transporter family were confirmed to exhibit paraquat transporter activity; furthermore, transporters such as DTX6 (detoxification efflux carrier) can export/sequestrate paraquat inside the cell to the vacuole and apoplast, which confers stronger paraquat resistance to nearly commercial doses. In addition, the evolving perspectives in paraquat resistance research integrating big data and artificial intelligence, development of paraquat-tolerant crops, and a proposal of ryegrass (Lolium. spp.) and/or goosegrass (Eleusine indica) as a model weed species for paraquat resistance studies were also briefly discussed. Further advances in elucidating the molecular mechanisms of paraquat resistance in plants, including weeds, are anticipated.