Characterization of three novel desaturases involved in the delta-6 desaturation pathways for polyunsaturated fatty acid
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BIOTECHNOLOGICALLY RELEVANT ENZYMES AND PROTEINS
Characterization of three novel desaturases involved in the delta-6 desaturation pathways for polyunsaturated fatty acid biosynthesis from Phytophthora infestans Quanxi Sun & Jiang Liu & Qin Zhang & Xiaohe Qing & Gary Dobson & Xinzheng Li & Baoxiu Qi
Received: 17 September 2012 / Revised: 15 November 2012 / Accepted: 22 November 2012 # Springer-Verlag Berlin Heidelberg 2012
Abstract Phytophthora infestans is the causative agent of potato blight that resulted in the great famine in Ireland in the nineteenth century. This microbe can release large amounts of the C20 very long-chain polyunsaturated fatty acids arachidonic acid (ARA; 20:4Δ5, 8, 11, 14) and eicosapentaenoic acid (EPA; 20:5Δ5, 8, 11, 14, 17) upon invasion that is known to elicit a hypersensitive response to their host plant. In order to identify enzymes responsible for the biosynthesis of these fatty acids, we blasted the recently fully sequenced P. infestans genome and identified three novel putatively encoding desaturase sequences. These were subsequently functionally characterized by expression in Saccharomyces cerevisiae and confirmed that they encode desaturases with Δ12, Δ6 and Δ5 activity, designated here as PinDes12, PinDes6 and PinDes5, respectively. This, together with the combined fatty acid profiles and a previously identified Δ6 elongase activity, implies that the ARA and EPA are biosynthesized predominantly via the Δ6 desaturation pathways in P. infestans. Elucidation of ARA and EPA biosynthetic mechanism may provide new routes to combating this potato blight microbe directly or by means of conferring resistance to important crops.
Q. Sun : J. Liu : Q. Zhang : X. Qing : X. Li (*) : B. Qi (*) State Key Laboratory of Crop Biology, Shandong Agricultural University, Tai’an 271000, China e-mail: [email protected] e-mail: [email protected] G. Dobson The James Hutton Institute, Invergowrie, Dundee DD2 5DA Scotland, UK B. Qi Department of Biology and Biochemistry, University of Bath, Bath BA2 7AY, UK e-mail: [email protected]
Keywords Potato blight . Phytophthora infestans . Arachidonic acid . Eicosapentaenoic acid . Desaturase . Δ6 desaturation pathways
Introduction Phytophthora infestans, an oomycete-related to organisms such as brown algae and diatoms, is the agent responsible for the devastating Irish potato famine. Early studies showed that extracts from the mycelium of P. infestans can elicit a hypersensitive response characterized by necrosis and accumulation of anti-microbial stress metabolites such as sesquiterpenoid phytoalexin in potato tubers, and the most active elicitors in these extracts were identified as arachidonic acid (ARA) and eicosapentaenoic acid (EPA) (Bostock et al. 1981, 1982; Larkin and Groves 2003). These two very long-chain polyunsaturated fatty acids (VLCPUFAs) are released from germinating spores of P. infestans onto their host plant tissue during infection. Further studies showed that both ARA and EPA can regulate enzyme activity involved in pathogen defence reacti
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