title: Herbicide phosphinothricin causes direct stimulation hormesis.
abstract: Herbicide phosphinothricin (PPT) inhibits glutamine synthetase (GS), a key enzyme in nitrogen assimilation, thus causing ammonia accumulation, glutamine depletion and eventually plant death. However, the growth response of Lotus corniculatus L. plants immersed in solutions with a broad range of PPT concentrations is biphasic, with pronounced stimulating effect on biomass production at concentrations ≤ 50 μM and growth inhibition at higher concentrations. The growth stimulation at low PPT concentrations is a result of activation of chloroplastic isoform GS2, while the growth suppression is caused by inhibition of both cytosolic GS1 and GS2 at higher PPT concentrations. Since the results are obtained in cell-free system (e.g. protein extracts), to which the principles of homeostasis are not applicable, this PPT effect is an unambiguous example of direct stimulation hormesis. A detailed molecular mechanism of concentration-dependent interaction of both PPT and a related GS inhibitor, methionine sulfoximine, with GS holoenzymes is proposed. The mechanism is in concurrence with all experimental and literature data.
authors: Institute for Biological Research "Siniša Stanković", Department for Plant Physiology, Bulevar despota Stefana 142, University of Belgrade, 11000 Belgrade, Serbia.
authors: Milan
authors: M
authors: Dragićević
authors: Jelena
authors: J
authors: Platiša
authors: Radomirka
authors: R
authors: Nikolić
authors: Slađana
authors: S
authors: Todorović
authors: Milica
authors: M
authors: Bogdanović
authors: Nevena
authors: N
authors: Mitić
authors: Ana
authors: A
authors: Simonović
keywords: Glufosinate; Glutamine synthetase; Hormesis; Lotus corniculatus L.; Methionine sulfoximine; Phosphinothricin
references: J Agric Food Chem. 2006 Feb 8;54(3):796-802
references: 16448185
references: Planta. 2000 Jan;210(2):252-60
references: 10664131
references: Anal Biochem. 1976 May 7;72:248-54
references: 942051
references: Plant Physiol. 1984 Jul;75(3):827-31
references: 16663712
references: Plant Cell Rep. 1998 Feb;17(4):256-261
references: 30736602
references: J Biol Chem. 2006 Sep 29;281(39):29287-96
references: 16829528
references: Plant Physiol. 2003 Sep;133(1):253-62
references: 12970491
references: Plant Cell Rep. 1995 Mar;14(6):380-4
references: 24185337
references: J Plant Physiol. 2003 Jun;160(6):601-5
references: 12872481
references: Mini Rev Med Chem. 2008 Aug;8(9):869-78
references: 18691144
references: Proc Natl Acad Sci U S A. 1968 Jan;59(1):164-70
references: 5242120
references: Planta. 1998 May;205(1):113-20
references: 9599808
references: Planta. 2006 Oct;224(5):1068-79
references: 16685525
references: Anal Biochem. 2004 Nov 15;334(2):312-7
references: 15494139
references: J Biol Chem. 1982 Jun 25;257(12):7246-51
references: 6123504
references: Biochemistry. 2001 Feb 20;40(7):1903-12
references: 11329256
references: Biochemistry. 1991 Jun 25;30(25):6135-41
references: 1676298
references: Biochemistry. 1969 Jun;8(6):2674-80
references: 4308004
references: Prikl Biokhim Mikrobiol. 2003 Nov-Dec;39(6):613-8
references: 14714472
references: Biotechnol Lett. 2007 May;29(5):785-9
references: 17279446
references: Planta. 1999 Oct;209(4):495-502
references: 10550631
references: Hum Exp Toxicol. 2002 Feb;21(2):91-7
references: 12102503
references: Helv Chim Acta. 1972 Jan 31;55(1):224-39
references: 5010035
references: Biochim Biophys Acta. 2000 Mar 7;1477(1-2):122-45
references: 10708854
references: Plant Physiol. 1980 Oct;66(4):619-23
references: 16661490
references: Toxicol Sci. 2001 Aug;62(2):330-8
references: 11452146
references: Dose Response. 2006 Oct 17;5(2):150-62
references: 18648603
references: Plant Physiol. 1987 Jan;83(1):155-8
references: 16665193
references: Nat Protoc. 2007;2(8):1849-61
references: 17703195
references: Plant Physiol. 1991 Apr;95(4):1057-62
references: 16668090
references: Biochem Biophys Res Commun. 1980 Jun 30;94(4):1207-12
references: 7396959
references: Rev Environ Contam Toxicol. 1994;138:73-145
references: 7938785
references: Annu Rev Plant Physiol Plant Mol Biol. 1996 Jun;47:569-593
references: 15012301