The molecular basis of multiple herbicide resistance in grass weeds

Lead Research Organisation: University of York
Department Name: Biology

Abstract

The current demands on global cereal production for food and biofuels production have placed renewed emphasis on the need for science and technologies to support sustainable and high yielding arable agriculture. A key component of efficient cereal production is the careful use of chemical control to suppress competing weeds. However, over the last 40 years the intensive use of herbicides has selected for populations of grass weeds which are resistant to selective graminicides (grass-killers) used in major cereals like wheat. In 1982 a new form of resistance was determined in a black-grass population in the UK which extended to all classes of herbicides licensed for its control in wheat and barley. Since then, incidences of multiple herbicide resistance (MHR) have become more frequent and have also developed in many other pernicious grass weeds. In extreme cases MHR weeds can devastate crops and can only be controlled by non-sustainable practices like deep ploughing. Recently, we have shown that a glutathione transferase (GST) termed AmGSTF1 is the causative agent of MHR in black-grass. Expression of the AmGSTF1 protein in other plants causes them to adopt the same unusual changes in their antioxidant defences seen in MHR black-grass. MHR plants behave as it they are being oxidatively stressed and this is n turn results in them becoming more resistant to chemicals including herbicides. Normally GSTs function to metabolize herbicides so a regulatory role for a family member in co-ordinating MHR was unexpected. Using our knowledge of medicinal chemistry, we have identified a class of chemicals which selectively bind to and inhibit AmGSTF1. If these synergists are co-applied with herbicides they can restore chemical control in MHR weeds and so this discovery is potentially an extremely important discovery in crop protection. We now propose to work with the agrochemical company Syngenta, which has its herbicide discovery centre located in the UK, to determine how AmGSTF1 causes MHR in black-grass by using these chemical inhibitors to disrupt its function. We also want to understand how the inhibitors bind selectively to AmGSTF1 so we can rationally design new synergists and establish if these compounds also work in a similar way in other grass weeds. Finally, there may be a positive aspect to MHR which we want to study. It is unlikely that the MHR response has evolved just to counteract herbicides. Instead, we suggest that AmGSTF1 signaling is an important part to the natural antioxidant stress response system of cereals and grass weeds. To test this possibility we will express the amgstf1 gene in other plants and determine whether or not the resulting changes in their biochemistry make them more resistant to adverse environmental conditions. At the conclusion of our studies we intend to understand the fundamental biology behind how AmGSTF1 functions to regulate MHR in grass weeds, have developed novel chemistries to block its activity and restore herbicide sensitivity and determined a potential new route to engineering stress tolerance in crops. Finally, our project may shed new insights into the mechanisms underlying multiple resistance to drugs and pesticides which have developed in animals and microbes.

Technical Summary

The acquisition of multiple herbicide resistance (MHR) in weeds such as black-grass (Alopecurus myosuroides) renders these plants tolerant to all classes of graminicides used in selective weed control in wheat and has been a growing problem over the last 25 years both in the UK and internationally. Building on earlier work, we have established that MHR in black-grass appears to be a specific type of stress response involving the upregulation of thiol and flavonoid antioxidants which is mediated by the aberrant up-regulation of a phi (F) class glutathione transferase, termed AmGSTF1. Thus expression of amGSTF1 in Arabidopsis caused a similar set of changes in thiol and flavonoid metabolism to that determined in MHR black-grass and this was associated with acquired tolerance to three classes of herbicides. Using a chemical intervention approach, we have shown that substituted benzoxadiazoles selectively inhibit AmGSTF1 and in so doing render MHR black-grass herbicide susceptible again. In a three year industrial partnership programme with agrochemicals company Syngenta we propose to study the primary mechanisms of AmGSTF1 signalling in black- grass using the inhibitors as functional probes to investigate binding partners and/or substrates of the enzyme. Using directed synthesis, we will generate a series of inhibitor chemistries to establish structure-activity relationships with respect to disrupting AmGSTF1 activity and counteracting herbicide resistance. These studies will be informed by determining inhibitor binding mechanism and protein structure such that new synergist chemistries can be rationally designed. AmGSTF1 function will then be assessed in transgenic plants and as we postulate its associated signaling activity is linked to responses to abiotic stress we will test these plants for alterations in their antioxidant metabolism and tolerance to adverse environmental conditions.

Publications

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Related Projects

Project Reference Relationship Related To Start End Award Value
BB/G006474/1 01/04/2009 31/10/2010 £533,730
BB/G006474/2 Transfer BB/G006474/1 01/10/2010 30/09/2012 £330,701
 
Description In the course of this grant we discovered that the specific protein AmGSTF1 is a functional biomarker on non-target site herbicide resistance in the problem weed black grass. This is a very important advance as this protein can be used as a diagnostic for herbicide resistance as well as a target for chemical synergists that can disrupt its activity and restore chemical control. This work has attracted in international attention and resulted in a major advance in our understanding of the resistance of pasts, weeds and pathogens to agrochemicals. The project exceeded the original objectives in that the foundational science we carried in the project has led to not only a much better understanding of the molecular basis of herbicide resistance but also practical tools that we can now use to give to the farming sector to help counteract the growth of resistance.
Exploitation Route We are currently working through the Centre for Crop Health and Protection with 3 major agronomy companies to develop a practical diagnostic device for in field testing of herbicide resistance. The diagnostic has been jointly developed with healthcare company MoLogic and we are currently beta-testing the devices with the farming industry prior to the commercial launch of the product in late 2018. The research underpinning this project is currently being continued though our currently supported Lola grant.
Sectors Agriculture, Food and Drink

 
Description The findings of this project contributed directly to founding the Black-grass Herbicide Resistance Initiative, which has been taken forward as a Lola. Other outputs include further funding from Syngenta and Bayer Crop Science for related work
First Year Of Impact 2014
Sector Agriculture, Food and Drink
Impact Types Economic,Policy & public services

 
Description BBSRC CASE studentship with Syngenta 
Organisation Syngenta International AG
Department Syngenta Crop Protection
Country United Kingdom 
Sector Private 
PI Contribution The studentship span out of the BBSRC grant allowing us to continue research leads in a new collaboration
Collaborator Contribution Syngenta hosted the CASE student , conducted wheat transformation studies and carried out extensive glasshouse trials for resistance testing
Impact This project helped support the award of the LOLA grant
Start Year 2010
 
Description BBSRC PhD CASE studentship with the Food and Environment Research Agency 
Organisation Fera Science Limited
Country United Kingdom 
Sector Public 
PI Contribution The outputs of the grant helped initiate a collaboration with Fera to develop a diagnostic for herbicide resistance in weeds
Collaborator Contribution Provided glass house growth facilities and diagnostics development services
Impact This was the starting point of our black grass diagnostics programme
Start Year 2012
 
Description CASE studentship with Croda 
Organisation Croda Europe Ltd
Country United Kingdom 
Sector Private 
PI Contribution Our research and expertise on the control of herbicide resistance using novel chemistries
Collaborator Contribution Expertise in herbicide formulation and advice on creating a spray testing facility at our research farm
Impact Work in progress
Start Year 2015
 
Description Innovation award with Syngenta 
Organisation Syngenta International AG
Department Syngenta Crop Protection
Country United Kingdom 
Sector Private 
PI Contribution Based on the outputs of the BBSRC grant we were funded to extend our working with Syngenta with their safener biology programme
Collaborator Contribution Syngenta wholly funded the grant and carried out the supporting safener biology in house
Impact This has built on our long term strategic relationship with Syngenta spanning weed biology, crop science and chemical discovery which has employed a Research Associate for 3 years
Start Year 2011
 
Title Methods and means relating to multiple herbicide resistance in plants 
Description The identification of a target for chemical intervention to counteract non-target site resistance in grass weeds and a chemical series able to act on that target. 
IP Reference WO2009034396 
Protection Patent application published
Year Protection Granted 2009
Licensed No
Impact The work on the protein has allowed us to develop it as a functional biomarker of herbicide resistance in diagnostics applications.
 
Description Interview on 'Food Unwrapped Episode 7 featuring stories on Wheat, Lard and Apple Juice' Aired Channel 4, 26th February 2018, 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Media (as a channel to the public)
Results and Impact TV interview with Paul Neve and Rob Edwards on our black grass work
Year(s) Of Engagement Activity 2018
URL http://www.channel4.com/programmes/food-unwrapped
 
Description Invited Speaker 58th Annual Meeting of the Weed Science Society of America, 'Herbicide metabolism in crops and weeds: a revisit, current understanding and new insights'. Crystal Gateway Marriott, Arlington, Virginia. 29th Jan-1st Feb 2018. 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Talk on our resistance project at the Weed Science Society of America Annual meeting
Year(s) Of Engagement Activity 2018
 
Description Plenary speaker and Chair of Crop Protection Module, CropWorld Global 2013 Conference 'Planting the Seeds of Innovation', Amsterdam RAI 29-30 October 2013. 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Industry/Business
Results and Impact Presentation to national industry congress on new approaches to crop protection
Year(s) Of Engagement Activity 2013
 
Description Plenary speaker at Westminster Food and Nutrition Forum 'Implementing the UK Strategy for Agricultural Technologies', Glaziers Hall, London 7th November 2013. 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Industry/Business
Results and Impact Presentation to policy forum on the value of agritechnology
Year(s) Of Engagement Activity 2013
 
Description Presentation at Resistance 2011 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Presentation on research arising from the grant on non target site herbicide resistance in black grass
Year(s) Of Engagement Activity 2011