Plant cytochrome P450-mediated herbicide metabolism

Abstract

In the last two decades it has become apparent that enzymes of the P450 monooxygenase (P450) superfamily are responsible for the Phase I metabolism of numerous herbicides representing several classes of organic compounds. The majority of experimental evidence for P450 involvement in herbicide metabolism has been derived from in vitro studies in which the catalytic activity of plant microsomes towards herbicidal substrates was measured in the presence of various P450 inhibitors and activators. While the studies with microsomes elicited much appreciation for the pivotal roles of plant P450s in herbicide metabolism, detailed characterization of these enzymes only became possible after the isolation of genes encoding specific isoforms responsible for herbicide conversion. Several lines of evidence suggest that the development of herbicide resistance in weeds by enhanced detoxification is frequently associated with elevated levels of P450 activity. Enhanced detoxification-based herbicide resistance is particularly difficult to control, because it can involve resistance to multiple, chemically unrelated classes of herbicides. Continued research efforts are aimed at elucidating the role of P450s in the metabolic fates of herbicides in plants and the development of herbicide resistance in weeds. Recent advances made in the isolation and genetic manipulation of P450 enzymes have created new opportunities for their application in engineering herbicide tolerance and bioremediation.

Safeners recruit multiple signalling pathways for the orchestrated induction of the cellular xenobiotic detoxification machinery in Arabidopsis

“…Indeed, variation in substrate specificity of GSTs and P450s in different plant species can result in herbicide selectivity (Barrett et al 1997;Van Eerd et al 2003;Yuan et al 2007;Zhang et al 2007a). Furthermore, GSTs with herbicidedetoxifying activity were shown to result in herbicide tolerance in dicots when overexpressed in appropriate tissues (Jepson et al 1997;Skipsey et al 2005;Benekos et al 2010), and the development of herbicide resistance in weeds is often because of increased activities of specific P450s (Siminszky 2006). The failure of safeners to induce herbicide tolerance in Arabidopsis and other dicots may thus be caused by the properties of the enzymes that are induced after safener treatment rather than a general lack of safener responsiveness.…”

In vitro biotransformation of PBDEs by root crude enzyme extracts: Potential role of nitrate reductase (NaR) and glutathione S-transferase (GST) in their debromination

“…CAT can catalyze the degradation of azo dyes (Paar et al, 2001). Hydoxylated metabolites of some herbicides in plants are predominantly formed via CYP450-mediated oxidation (Siminszky, 2006). NaR and GST were reported to mediate the reductive degradation of PCBs and some explosives (Blanchette and Singh, 2003;Anke et al, 2003;Medina et al, 2004;Magee et al, 2008).…”

Genetic control of a cytochrome P450 metabolism-based herbicide resistance mechanism in Lolium rigidum

“…Herbicide metabolism/ detoxification catalysed by cytochrome P450 enzymes is a prominent herbicide resistance mechanism evolved in some herbicide resistant weed populations (Powles and Yu, 2010). The current understanding of P450-mediated herbicide metabolism in plants suggests that likely there are multiple P450 isoforms with varying herbicide (substrate) specificity, thus variable capacity for herbicide metabolism (Siminszky, 2006;Powles and Yu, 2010). However, the molecular identification of specific P450 genes endowing herbicide resistance by metabolism remains to be elucidated.…”