High Resistance to Quinclorac in Multiple-Resistant Echinochloa colona Associated with Elevated Stress Tolerance Gene Expression and Enriched Xenobiotic Detoxification Pathway

Abstract

Echinochloa colona and other species in this genus are a threat to global rice production and food security. Quinclorac, an auxin mimic, is a common herbicide for grass weed control in rice, and Echinochloa spp. have evolved resistance to it. The complete mode of quinclorac action and subsequent evolution of resistance is not fully understood. We analyzed the de novo transcriptome of multiple-herbicide-resistant (ECO-R) and herbicide-susceptible genotypes in response to quinclorac. Several biological processes were constitutively upregulated in ECO-R, including carbon metabolism, photosynthesis, and ureide metabolism, indicating improved metabolic efficiency. The transcriptional change in ECO-R following quinclorac treatment indicates an efficient response, with upregulation of trehalose biosynthesis, which is also known for abiotic stress mitigation. Detoxification-related genes were induced in ECO-R, mainly the UDP-glycosyltransferase (UGT) family, most likely enhancing quinclorac metabolism. The transcriptome data also revealed that many antioxidant defense elements were uniquely elevated in ECO-R to protect against the auxin-mediated oxidative stress. We propose that upon quinclorac treatment, ECO-R detoxifies quinclorac utilizing UGT genes, which modify quinclorac using the sufficient supply of UDP-glucose from the elevated trehalose pathway. Thus, we present the first report of upregulation of trehalose synthesis and its association with the herbicide detoxification pathway as an adaptive mechanism to herbicide stress in Echinochloa, resulting in high resistance.

Molecular Mechanisms of Herbicide Resistance in Weeds

“…Among grasses, Echinochloa ssp. is reported in two articles [ 9 , 14 ] and L. multiflorum in one [ 8 ]; among dicots, two articles reported on the global invasive weed species A. palmeri [ 10 , 13 ]. All these weeds are acknowledged to be among the top 10 weed species resistant to most SoAs globally [ 19 ].…”

“…Interestingly, information on the resistance to auxins in Echinochloa ssp. [ 14 ], microtubule assembly [ 13 ], and PPO inhibitors [ 10 ], both in A. palmeri , are contributions of this Special Issue.…”

“…Among NTSR mechanisms, most articles cover an enhanced metabolism involving different enzyme families and degradation pathways. One contribution referred to P450 [ 12 ] and two to GST [ 12 , 13 ], the most important enzyme families involved in herbicide degradation, while two other contributions highlighted that stress-responsive genes were involved in herbicide metabolism [ 12 , 14 ].…”

“…The detailed SoA of quinclorac, a synthetic auxin with herbicide activity against grass weeds, is not fully understood, and the same is true for the potential resistance mechanisms evolving in weeds. A contribution to this Special Issue tried to unravel the resistance mechanisms of E. colona to this herbicide using a de novo transcriptome approach [ 14 ]. Data showed that carbon metabolism, photosynthesis, and ureide metabolism, all indicating improved metabolic efficiency, were upregulated in the resistant population.…”

Germination Characteristics Associated With Glutathione S-Transferases Endowed Quizalofop-p-Ethyl Resistance in Polypogon fugax

“…Some PSCS and CDPK genes were involved in the regulation of proline biosynthesis and the translation of phosphorylation signals, respectively, and both played a role in responding to abiotic stress in plants ( Franz et al, 2011 ; Asano et al, 2012 ). Recent studies have shown that herbicides stress could induce changes in the transcription levels of P5CS and CDPK genes in plants ( Boulahia et al, 2016 ; Wang et al, 2021 ; Rangani et al, 2022 ). It was reported that P5CS activity and its gene expression level were reduced by exogenous application of ethanolamine ( Rajaeian et al, 2017 ).…”