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

Ahmad L
(2017)
Structural evidence for Arabidopsis glutathione transferase AtGSTF2 functioning as a transporter of small organic ligands.
in FEBS open bio

Cummins I
(2011)
Multiple roles for plant glutathione transferases in xenobiotic detoxification.
in Drug metabolism reviews

Cummins I
(2013)
Key role for a glutathione transferase in multiple-herbicide resistance in grass weeds.
in Proceedings of the National Academy of Sciences of the United States of America

Sabbadin F
(2017)
Transcriptome sequencing identifies novel persistent viruses in herbicide resistant wild-grasses.
in Scientific reports
Related Projects
Project Reference | Relationship | Related To | Start | End | Award Value |
---|---|---|---|---|---|
BB/G006474/1 | 31/03/2009 | 30/10/2010 | £533,730 | ||
BB/G006474/2 | Transfer | BB/G006474/1 | 30/09/2010 | 29/09/2012 | £327,424 |
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 | METHOD AND MEANS RELATING TO MULTIPLE HERBICIDE RESISTANCE IN PLANTS |
Description | Methods for overcoming multiple herbicide resistance (MHR) in plants using inhibitors of GST suppression of Formula (I), novel chemical inhibitors of Formula (Ia), compositions comprising compounds of Formula (I), and uses and methods relating thereto. |
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 |