In tobacco, an elicitor- and pathogen-induced 9-lipoxygenase (LOX) gene (NtLOX1) was previously shown by our group to be essential for resistance to pathogens, notably Phytophthora parasitica var. nicotianae (Ppn). In the present work, a search for tobacco genes encoding enzymes of the oxylipin pathway possibly acting downstream of NtLOX1 was undertaken, and resulted in the cloning and characterisation of a divinyl ether synthase (DES) clone (NtDES1; CYP74D). We show that NtDES1 is a 9-DES specifically converting fatty acid 9-hydroperoxides into divinyl ether fatty acids. NtDES1 has the potential to act in combination with NtLOX1, since in the presence of the two enzymes, linoleic and linolenic acids were converted in vitro into colneleic and colnelenic acids, respectively. Interestingly, the pattern of NtDES1 gene expression is quite similar to that of NtLOX1. NtDES1 transcript is undetected in healthy tissues from different plant organs, and locally and transiently accumulate after elicitation and fungal infection but not after wounding. Like NtLOX1, NtDES1 transcript level increases following treatment of tobacco cells with (MeJA). Visualisation of a NtDES1-GFP fusion protein in tobacco protoplasts indicated that NtDES1 is cytosolic, consistent with the presumed location of 9-LOXs in plants. Our data strongly suggest that, in tobacco, NtDES1 and NtLOX1 act together to form divinyl ethers in response to pathogen attack.
A divinyl ether synthase specifically associated with elicitation and pathogenesis in N. tabacum
CARDINALE, Francesca;
2003-01-01
Abstract
In tobacco, an elicitor- and pathogen-induced 9-lipoxygenase (LOX) gene (NtLOX1) was previously shown by our group to be essential for resistance to pathogens, notably Phytophthora parasitica var. nicotianae (Ppn). In the present work, a search for tobacco genes encoding enzymes of the oxylipin pathway possibly acting downstream of NtLOX1 was undertaken, and resulted in the cloning and characterisation of a divinyl ether synthase (DES) clone (NtDES1; CYP74D). We show that NtDES1 is a 9-DES specifically converting fatty acid 9-hydroperoxides into divinyl ether fatty acids. NtDES1 has the potential to act in combination with NtLOX1, since in the presence of the two enzymes, linoleic and linolenic acids were converted in vitro into colneleic and colnelenic acids, respectively. Interestingly, the pattern of NtDES1 gene expression is quite similar to that of NtLOX1. NtDES1 transcript is undetected in healthy tissues from different plant organs, and locally and transiently accumulate after elicitation and fungal infection but not after wounding. Like NtLOX1, NtDES1 transcript level increases following treatment of tobacco cells with (MeJA). Visualisation of a NtDES1-GFP fusion protein in tobacco protoplasts indicated that NtDES1 is cytosolic, consistent with the presumed location of 9-LOXs in plants. Our data strongly suggest that, in tobacco, NtDES1 and NtLOX1 act together to form divinyl ethers in response to pathogen attack.
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