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Abstract Detail


Busta, Lucas [1], Yim, Won Cheol [2], LaBrant, Evan W. [3], Grimes, Lindsey [4], Wahrenburg, Zach [4], Santos, Patricia [4], Kosma, Dylan [4], Cahoon, Edgar B. [1].

The diversity, activity, and biosynthesis of bioactive polyacetylenes in Daucus carota.

Polyacetylenic lipids are produced in various Apiaceae and Asteraceae species in response to pathogen attack. It has long been suspected that these compounds are natural pesticides; a potentially valuable resource for creating crops with enhanced pathogen resistance.The recent release of a high-quality carrot genome has enabled functional genomics approaches to exploring polyacetylene structure, function, and biosynthesis in this species. We began with a detailed analysis of carrot polyacetylene chemical structures and distribution among carrot tissues in the cultivar Danvers. We identified five major (two novel) and seven trace polyacetylenes, with falcarindiol and falcarinol predominating. In this cultivar, total polyacetylene concentrations were around 2 μg/mg. At this concentration, we found that purified falcarinol inhibited the growth rate of mycelia of the necrotrophic fungus Sclerotinia sclerotiorum by 25%. Next, an analysis of five carrot cultivars revealed falcarinol levels ranging from ca. 1 to 5 μg/cm2 that were positively correlated with resistance to S. sclerotiorum. These data provided a rationale and framework for searching for underlying biosynthetic genes. Previous work had identified that the polyacetylene biosynthesis begins with the conversion of the monounsaturated fatty acid oleate into the polyunsaturated, acetylenic fatty acid dehydrocrepenynate. In other plant species, these steps are catalyzed by members of the fatty acid desaturase (FAD2) family. We found that the carrot FAD2 family is massive, with 24 members. To identify carrot FAD2s associated with polyacetylene production, we correlated polyacetylene abundance with both public RNAseq data from diverse carrot tissues and RNAseq data from carrot cell cultures before and after elicitation with an extract of fungal mycelia. By testing top candidate genes in yeast and/or Arabidopsis seeds, we identified carrot genes capable of generating dehydrocrepenynate. We are now (i) creating knockout and overexpression lines with altered polyacetylene content to test their pathogen resistance and (ii) examining the evolution of polyacetylene biosynthesis and structure in the euasterid clade.

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1 - University of Nebraska, Biochemistry, 1901 Vine St., Lincoln, NE, 68588, United States
2 - University of Nevada, Biochemistry and Molecular Biology, Reno, NV
3 - University of Nebraska, Beadle Center, 1901 Vine St., Lincoln, NE, 68588, United States
4 - University of Nevada, Biochemistry and Molecular Biology, Reno, NV, 89557

plant-fungus interaction

Presentation Type: Oral Paper
Session: 44, Physiology
Location: 114/Mayo Civic Center
Date: Wednesday, July 25th, 2018
Time: 2:45 PM
Number: 44006
Abstract ID:976
Candidate for Awards:Physiological Section Best Paper Presentation

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