AHAS herbicide resistance endowing mutations : Effect on AHAS functionality and plant growth

• Autores: Yu, Qin; Han, Heping; Vila Aiub, Martín Miguel; Powles, Stephen B.
• Año de publicación: 2010
• Idioma: inglés
• Tipo de recurso: artículo
• Fuente: Journal of Experimental Botany; Vol.61, no.14; 3925-3934; https://academic.oup.com/jxb
• Materia: AHAS RESISTANCE MUTATION; ENZYME KINETICS; HERBICIDE RESISTANCE; RELATIVE GROWTH RATE; ACETOLACTATE SYNTHASE; BRANCHED CHAIN AMINO ACID; HERBICIDE; DRUG ANTAGONISM; DRUG EFFECT; ENZYMOLOGY; GENETICS; GROWTH, DEVELOPMENT AND AGING; HERBICIDE RESISTANCE; HOMOZYGOTE; LOLIUM; METABOLISM; MUTATION; ACETOLACTATE SYNTHASE; AMINO ACID SUBSTITUTION; AMINO ACIDS, BRANCHED-CHAIN; HERBICIDES; HOMOZYGOTE; LOLIUM RIGIDUM
• Institución: Universidad de Buenos Aires. Facultad de Agronomía

Fil: Yu, Qin. University of Western Australia (UWA). School of Agriculture and Environment. Australian Herbicide Resistance Initiative (AHRI). Crawley, Western Australia, Australia.
Fil: Han, Heping. University of Western Australia (UWA). School of Agriculture and Environment. Australian Herbicide Resistance Initiative (AHRI). Crawley, Western Australia, Australia.
Fil: Vila Aiub, Martín Miguel. University of Western Australia (UWA). School of Agriculture and Environment. Australian Herbicide Resistance Initiative (AHRI). Crawley, Western Australia, Australia.
Fil: Vila Aiub, Martín Miguel. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura (IFEVA). Buenos Aires, Argentina.
Fil: Vila Aiub, Martín Miguel. CONICET – Universidad de Buenos Aires. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura (IFEVA). Buenos Aires, Argentina.
Fil: Powles, Stephen B. University of Western Australia (UWA). School of Agriculture and Environment. Australian Herbicide Resistance Initiative (AHRI). Crawley, Western Australia, Australia.
Twenty-two amino acid substitutions at seven conserved amino acid residues in the acetohydroxyacid synthase (AHAS) gene have been identified to date that confer target-site resistance to AHAS-inhibiting herbicides in biotypes of field-evolved resistant weed species. However, the effect of resistance mutations on AHAS functionality and plant growth has been investigated for only a very few mutations. This research investigates the effect of various AHAS resistance mutations in Lolium rigidum on AHAS functionality and plant growth. The enzyme kinetics of AHAS from five purified L. rigidum populations, each homozygous for the resistance mutations Pro-197-Ala, Pro-197-Arg, Pro-197-Gln, Pro-197-Ser or Trp-574-Leu, were characterized and the pleiotropic effect of three mutations on plant growth was assessed via relative growth rate analysis. All these resistance mutations endowed a herbicide-resistant AHAS and most resulted in higher extractable AHAS activity, with no-to-minor changes in AHAS kinetics. The Pro-197-Arg mutation slightly (but significantly) increased the K m for pyruvate and remarkably increased sensitivity to feedback inhibition by branched chain amino acids. Whereas the Pro-197-Ser and Trp-574-Leu mutations exhibited no significant effects on plant growth, the Pro-197-Arg mutation resulted in lower growth rates. It is clear that, at least in L. rigidum, these five AHAS resistance mutations have no major impact on AHAS functionality and hence probably no plant resistance costs. These results, in part, explain why so many Pro-197 AHAS resistance mutations in AHAS have evolved and why the Pro-197-Ser and the Trp-574-Leu AHAS resistance mutations are frequently found in many weed species.