Isoforms of acetyl-coenzyme a carboxylase in Lolium multiflorum

K. J. Evenson, J. W. Gronwald, D. L. Wyse

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Two multifunctional acetyI-CoA carboxylase (ACCase, EC isoforms were isolated from etiolated and mature leaves of Italian ryegrass (Lolium multiflorum Lam.). ACCase I and ACCase II eluted from a TMAE (trimethylaminoethyl) anion exchange column at approximately 275 and 195 mM KCl, respectively. Both isoforms were dimers with 206 kD subunits. ACCase 1 represented 95% and 66% of total ACCase activity in 3-week-old and etiolated leaves, respectively. Total activity of ACCase I and ACCase II decreased by 35% and 90% during greening of etiolated leaves, respectively. There were no differences in total or specific activities of ACCase I isolated from leaves of diclofop-resistant and -susceptible Lolium multiflorum biotypes. However, ACCase I from the resistant biotype was tolerant to diclofop [I50 (herbicide concentration resulting in 50% inhibition of activity) = 7.0 μM] while ACCase I from the susceptible biotype was sensitive (I50 = 0.2 μM). ACCase II activity was relatively insensitive to diclofop (I50 > 125 μM) in both diclofop-resistant and -susceptible biotypes. Polyclonal antiserum to the plastid-localized ACCase I isoform from maize cross-reacted with the 206-kD polypeptides of both ACCase I and ACCase II. ACCase I and II differed in their affinity to monomeric avidin; ACCase I did not bind to monomeric avidin while ACCase II did bind. The results indicate that Lolium leaves contain two distinct, multifunctional ACCase isoforms and that diclofop resistance is due to a change in herbicide sensitivity of the predominant isoform (ACCase I).

Original languageEnglish (US)
Pages (from-to)265-272
Number of pages8
JournalPlant Physiology and Biochemistry
Issue number4
StatePublished - Jan 1 1997


  • ACCase
  • Acetyl coenzyme A carboxylase
  • diclofop
  • herbicide
  • herbicide resistance
  • Lolium multiflorum


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