Desorption electrospray ionization mass spectrometry reveals surface-mediated antifungal chemical defense of a tropical seaweed
- Amy L. Lanea,1,
- Leonard Nyadonga,
- Asiri S. Galhenaa,
- Tonya L. Shearerb,
- E. Paige Stouta,
- R. Mitchell Parryc,
- Mark Kwasnika,
- May D. Wangc,
- Mark E. Hayb,
- Facundo M. Fernandeza and
- Julia Kubaneka,b,2
- aSchool of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA 30332;
- bSchool of Biology, Georgia Institute of Technology, Atlanta, GA 30332; and
- cWallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA 30332
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Edited by Jerrold Meinwald, Cornell University, Ithaca, NY, and approved March 3, 2009 (received for review November 26, 2008)
Abstract
Organism surfaces represent signaling sites for attraction of allies and defense against enemies. However, our understanding of these signals has been impeded by methodological limitations that have precluded direct fine-scale evaluation of compounds on native surfaces. Here, we asked whether natural products from the red macroalga Callophycus serratus act in surface-mediated defense against pathogenic microbes. Bromophycolides and callophycoic acids from algal extracts inhibited growth of Lindra thalassiae, a marine fungal pathogen, and represent the largest group of algal antifungal chemical defenses reported to date. Desorption electrospray ionization mass spectrometry (DESI-MS) imaging revealed that surface-associated bromophycolides were found exclusively in association with distinct surface patches at concentrations sufficient for fungal inhibition; DESI-MS also indicated the presence of bromophycolides within internal algal tissue. This is among the first examples of natural product imaging on biological surfaces, suggesting the importance of secondary metabolites in localized ecological interactions, and illustrating the potential of DESI-MS in understanding chemically-mediated biological processes.
Footnotes
- 2To whom correspondence should be addressed. E-mail: julia.kubanek{at}biology.gatech.edu
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Author contributions: A.L.L., F.M.F., and J.K. designed research; A.L.L., L.N., A.S.G., T.L.S., E.P.S., R.M.P., M.K., M.D.W., F.M.F., M.E.H., and J.K. performed research; L.N., A.S.G., and M.K. contributed new reagents/analytic tool; A.L.L., F.M.F., and J.K. analyzed data; and A.L.L. and J.K. wrote the paper.
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↵1Present address: Scripps Institution of Oceanography, University of California at San Diego, 9500 Gilman Drive, La Jolla, CA 92093.
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The authors declare no conflict of interest.
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This article is a PNAS Direct Submission.
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See Commentary on page 7269.
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This article contains supporting information online at www.pnas.org/cgi/content/full/0812020106/DCSupplemental.
