Identification of Genes Encoding Enzymes Catalyzing the Early Steps of Carrot Polyacetylene Biosynthesis.

Resource Type: 
Publication
Publication Type: 
Journal Article
Title: 
Identification of Genes Encoding Enzymes Catalyzing the Early Steps of Carrot Polyacetylene Biosynthesis.
Authors: 
Busta L, Yim WC, LaBrant EW, Wang P, Grimes L, Malyszka K, Cushman JC, Santos P, Kosma DK, Cahoon EB
Series Name: 
Plant physiology
Journal Abbreviation: 
Plant Physiol.
Volume: 
178
Issue: 
4
Page Numbers: 
1507-1521
Publication Year: 
2018
Publication Date: 
2018 12
DOI: 
10.1104/pp.18.01195
ISSN: 
1532-2548
EISSN: 
1532-2548
Cross Reference: 
PMIDLoading content
Citation: 
Busta L, Yim WC, LaBrant EW, Wang P, Grimes L, Malyszka K, Cushman JC, Santos P, Kosma DK, Cahoon EB. Identification of Genes Encoding Enzymes Catalyzing the Early Steps of Carrot Polyacetylene Biosynthesis.. Plant physiology. 2018 12; 178(4):1507-1521.
Abstract: 

Polyacetylenic lipids accumulate in various Apiaceae species after pathogen attack, suggesting that these compounds are naturally occurring pesticides and potentially valuable resources for crop improvement. These compounds also promote human health and slow tumor growth. Even though polyacetylenic lipids were discovered decades ago, the biosynthetic pathway underlying their production is largely unknown. To begin filling this gap and ultimately enable polyacetylene engineering, we studied polyacetylenes and their biosynthesis in the major Apiaceae crop carrot (Daucus carota subsp. sativus). Using gas chromatography and mass spectrometry, we identified three known polyacetylenes and assigned provisional structures to two novel polyacetylenes. We also quantified these compounds in carrot leaf, petiole, root xylem, root phloem, and root periderm extracts. Falcarindiol and falcarinol predominated and accumulated primarily in the root periderm. Since the multiple double and triple carbon-carbon bonds that distinguish polyacetylenes from ubiquitous fatty acids are often introduced by Δ12 oleic acid desaturase (FAD2)-type enzymes, we mined the carrot genome for FAD2 genes. We identified a FAD2 family with an unprecedented 24 members and analyzed public, tissue-specific carrot RNA-Seq data to identify coexpressed members with root periderm-enhanced expression. Six candidate genes were heterologously expressed individually and in combination in yeast and Arabidopsis (Arabidopsis thaliana), resulting in the identification of one canonical FAD2 that converts oleic to linoleic acid, three divergent FAD2-like acetylenases that convert linoleic into crepenynic acid, and two bifunctional FAD2s with Δ12 and Δ14 desaturase activity that convert crepenynic into the further desaturated dehydrocrepenynic acid, a polyacetylene pathway intermediate. These genes can now be used as a basis for discovering other steps of falcarin-type polyacetylene biosynthesis, to modulate polyacetylene levels in plants, and to test the in planta function of these molecules.

Publication Model: 
Print-Electronic
Language: 
English
Language Abbr: 
eng
Journal Country: 
United States