Diseño racional de variantes mutantes de la enzima acetohidroxiácido sintasa de quinua (Chenopodium quinoa) resistentes a herbicidas comerciales

Abstract

The enzyme acetohydroxy acid synthase (AHAS) plays a crucial role in the biosynthesis of branched-chain amino acids in plants and microorganisms. This enzyme is the target of five families of commercial herbicides, among which sulphonylureas and imidazolinones stand out for their excellent biocidal activity on weeds and low toxicity to animals. Herbicides that act on AHAS are applied globally on different important crops such as rice, soybean, barley, wheat, cotton and maize. However, for quinoa, no herbicide has yet been identified for weed control. In the present study, two different mutant variants of the quinoa AHAS enzyme were modelled which aim to generate resistance to the herbicides chlorimuron ethyl (CE) and imazaquin (IQ). The high degree of AHAS conservation in the different plant species allowed us to generate a computational model of the C. quinoa AHAS structure based on the 3D structure of Arabidopsis thaliana AHAS. Based on the wild-type CqAHAS model, the A114T and P189S mutations were modelled, and their effect on the binding mode of the herbicides CE and IQ was analysed. The results led to the conclusion that the A114T mutation could lead to some degree of resistance to IQ, while the P189S mutation could lead to high resistance to CE. This study demonstrates the concept that the introduction of mutations in the AHAS enzyme of quinoa can be effective in introducing resistance to commercial herbicides for integrated weed management.