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Applied and Environmental Microbiology, March 2007, p. 1921-1927, Vol. 73, No. 6
0099-2240/07/$08.00+0     doi:10.1128/AEM.02479-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Screening Marine Fungi for Inhibitors of the C4 Plant Enzyme Pyruvate Phosphate Dikinase: Unguinol as a Potential Novel Herbicide Candidate{triangledown}

Cherie A. Motti,1* David G. Bourne,1 James N. Burnell,2 Jason R. Doyle,1 Dianne S. Haines,2 Catherine H. Liptrot,1 Lyndon E. Llewellyn,1 Shilo Ludke,2 Andrew Muirhead,1 and Dianne M. Tapiolas1

Australian Institute of Marine Science, Townsville, Queensland, Australia,1 Department of Biochemistry and Molecular Biology, James Cook University, Townsville, Queensland, Australia2

Received 23 October 2006/ Accepted 27 December 2006

A total of 2,245 extracts, derived from 449 marine fungi cultivated in five types of media, were screened against the C4 plant enzyme pyruvate phosphate dikinase (PPDK), a potential herbicide target. Extracts from several fungal isolates selectively inhibited PPDK. Bioassay-guided fractionation of one isolate led to the isolation of the known compound unguinol, which inhibited PPDK with a 50% inhibitory concentration of 42.3 ± 0.8 µM. Further kinetic analysis revealed that unguinol was a mixed noncompetitive inhibitor of PPDK with respect to the substrates pyruvate and ATP and an uncompetitive inhibitor of PPDK with respect to phosphate. Unguinol had deleterious effects on a model C4 plant but no effect on a model C3 plant. These results indicate that unguinol inhibits PPDK via a novel mechanism of action which also translates to an herbicidal effect on whole plants.

* Corresponding author. Mailing address: Australian Institute of Marine Science, PMB 3, Townsville, Queensland, Australia 4810. Phone: 61-7-4753 4143. Fax: 61-7-4772 5782. E-mail: c.motti{at}aims.gov.au.

{triangledown} Published ahead of print on 12 January 2007.

Applied and Environmental Microbiology, March 2007, p. 1921-1927, Vol. 73, No. 6
0099-2240/07/$08.00+0     doi:10.1128/AEM.02479-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.





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