A role for glutathioneS-transferases in resistance to herbicides in grasses

Abstract

Herbicide resistance is the heritable ability of a weed biotype or population to survive a herbicide application that would effectively kill a susceptible population of the weed. In the U.K. the most widespread and financially important herbicide-resistant weed is blackgrass. Investigations to elucidate the molecular mechanisms conferring herbicide resistance to blackgrass populations have been ongoing for two decades. Although the identification of target site–resistant populations has proved to be relatively straightforward (using, for example, target site assays in vitro), the study and understanding of resistance mechanisms involved in enhanced metabolism has proven to be more problematic. Research has focused on the cytochrome P450 monooxygenase and glutathione S-transferase (GST) enzyme families, both of which have been shown to be important in herbicide metabolism in many weed and crop species. GST activity and abundance are greater in a selection of herbicide-resistant blackgrass biotypes, and herbicide treatment of field populations of blackgrass results in the survival of the proportion of population possessing the greatest GST activity and abundance. In addition, GST activity in the field increases between winter and spring, and this coincides with reduced efficacy of important blackgrass herbicides. GST activities within field populations of blackgrass are highly varied, and this plasticity is discussed in relation to the development of resistant populations in field situations. This article describes research results in blackgrass and compares them with GST studies in other weed species as well as with other mechanisms for enhanced metabolism-based resistance.

Differential Responses to Preemergence and Postemergence Atrazine in Two Atrazine‐Resistant Waterhemp Populations

“…Fenoxaprop-P-ethyl and chlorotoluron are herbicide substrates for GST-mediated metabolism in naturally-tolerant cereal crops and NTSR grass populations (Tal et al, 1993;Reade et al, 2004;Cummins et al, 2013). Additionally, preliminary greenhouse trials demonstrated that NBD-Cl at 270 g ha -1 exhibited an optimal increase in atrazine activity (PRE and POST) without displaying visual injury symptoms or secondary phytotoxic effects (data not shown).…”

“…Along these lines, current research in our laboratory is investigating the hypothesis that similar but distinct GSTbased NTSR mechanisms for atrazine occur in these two waterhemp populations (Evans et al, 2013). The NTSR and MHR mechanisms in grass (Reade et al, 2004;Délye et al, 2011;Cummins et al, 2013) and dicot (Patzoldt et al, 2005;Ma et al, 2013;Scarabel et al, 2015) weeds are providing complex new challenges for weed management and crop production by limiting effective herbicide options available (Preston, 2004;Yu and Powles, 2014). In addition to understanding cross-resistance patterns, genetic and biochemical mechanisms, and the molecular basis for NTSR and MHR in weeds, novel management tools are needed to combat herbicide-resistant weeds or overcome the mechanism(s) that confer resistance to both PRE and POST herbicides (Preston, 2004).…”

Interação entre nematicidas e herbicidas aplicados no plantio da cana-de-açúcar

“…O volume de chuvas após a aplicação (Tabela 3) foi suficiente para lixiviar os herbicidas até a região das raízes das plantas, e, nessa situação, eles foram absorvidos juntamente com os nematicidas. Como a detoxificação de produtos primários absorvidos, como herbicidas e nematicidas, é feita por várias enzimas, entre as quais a citocromo P450 monooxigenase (Hatzios & Burgos, 2004;Reade et al, 2004), existente em quantidade limitada no interior da planta, a absorção de herbicida e nematicida provavelmente sobrecarregou o sistema metabólico das plantas, que passaram a manifestar sintomas de intoxicação, classicamente iniciados por clorose seguida por necrose foliar. Significância dos valores de F: ** = 1%, * = 5%, + = 10% e ns = não-significativo.…”

Creation of herbicide-tolerant crops by gene targeting

“…For example, glutathione S-transferases (GSTs) are families of multifunctional enzymes that catalyze the conjugation of glutathione to a variety of electrophilic and hydrophobic substrates. GSTs are involved in stress responses, and, in some crop and weed species, some herbicides are detoxified by glutathione conjugation (for reviews, see [75][76][77] ). Herbicide-metabolizing GSTs have been purified and characterized from several crops (for reviews, see 75,78) ).…”