Upon interaction with a pathogen, plants activate several metabolic responses leading to the formation of defence substances, among which oxylipins. Lipoxygenase (LOX) enzymatic products can feed into several anabolic pathways, among which the one leading to jasmonates via allene oxide synthase and the one to divinyl ethers via divinyl ether synthase (DES). Because of the possible multiple metabolic outcomes for LOX action, it is unclear which oxylipin category could be responsible for the altered phenotype observed upon elicitation or pathogenesis in NtLOX1 sense and antisense tobacco plants, indicating a positive role for NtLOX1 in the resistant phenotype to race 1 of Phytophthora parasitica var. nicotianae (Ppn). The best-characterized oxylipin in defence is perhaps jasmonate. However, preliminary results indicate that NtLOX1 activity doesn’t influence the levels of jasmonate and jasmonate-like molecules. In elicitor- or pathogen-challenged Nicotiana tabacum plants, a 9-LOX pathway is initiated by NtLOX1. Therefore, in the search for 9-hydroperoxide-degrading enzymes functionally downstream of NtLOX1, we cloned and characterised a divinyl ether synthase (NtDES1) from elicited tobacco cells whose expression is spatially and temporally coordinated with the activity of NtLOX1. The aim of our study is to assess unequivocally if divinyl ethers produced by NtDES1 action downstream of NtLOX1, or else other molecular species, are indeed responsible for NtLOX1 role in defence. To this purpose, a metabolic profiling approach was taken, which will define the oxylipin signature and its differences from WT in stable and homozygous transgenic tobacco plants (NtLOX1 sense and antisense) upon elicitation and infection by Ppn.
Which oxylipin is responsible for the altered phenotype of LOX sense and antisense tobacco plants during pathogenesis and elicitation?
CARDINALE, Francesca
2004-01-01
Abstract
Upon interaction with a pathogen, plants activate several metabolic responses leading to the formation of defence substances, among which oxylipins. Lipoxygenase (LOX) enzymatic products can feed into several anabolic pathways, among which the one leading to jasmonates via allene oxide synthase and the one to divinyl ethers via divinyl ether synthase (DES). Because of the possible multiple metabolic outcomes for LOX action, it is unclear which oxylipin category could be responsible for the altered phenotype observed upon elicitation or pathogenesis in NtLOX1 sense and antisense tobacco plants, indicating a positive role for NtLOX1 in the resistant phenotype to race 1 of Phytophthora parasitica var. nicotianae (Ppn). The best-characterized oxylipin in defence is perhaps jasmonate. However, preliminary results indicate that NtLOX1 activity doesn’t influence the levels of jasmonate and jasmonate-like molecules. In elicitor- or pathogen-challenged Nicotiana tabacum plants, a 9-LOX pathway is initiated by NtLOX1. Therefore, in the search for 9-hydroperoxide-degrading enzymes functionally downstream of NtLOX1, we cloned and characterised a divinyl ether synthase (NtDES1) from elicited tobacco cells whose expression is spatially and temporally coordinated with the activity of NtLOX1. The aim of our study is to assess unequivocally if divinyl ethers produced by NtDES1 action downstream of NtLOX1, or else other molecular species, are indeed responsible for NtLOX1 role in defence. To this purpose, a metabolic profiling approach was taken, which will define the oxylipin signature and its differences from WT in stable and homozygous transgenic tobacco plants (NtLOX1 sense and antisense) upon elicitation and infection by Ppn.
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