Show simple item record

dc.contributor.author Strelkov, Stephen E. en_US
dc.date.accessioned 2007-05-15T15:18:23Z
dc.date.available 2007-05-15T15:18:23Z
dc.date.issued 1997-12-01T00:00:00Z en_US
dc.identifier.uri http://hdl.handle.net/1993/829
dc.description.abstract Pyrenophora tritici-repentis differentially induces tan necrosis and extensive chlorosis in its hexaploid wheat host. A chlorosis inducing host-specific toxin, termed the Ptr chlorosis toxin, has been identified from race 5 of P. tritici-repentis. Ptr chlorosis toxin was purified from the culture filtrates of race 5 isolates, and the physiological development of chlorosis was investigated. Partial purification was performed by 25-80% ammonium sulfate precipitation and passage through a CM-S C25 cation exchange column. Final purification was performed on fast performance liquid chromatogra hy (FPLC), using a MonoS 5/5 cation exchanger, followed by size fractionation on a Superose 12 HR 10/30 column. Purity was confirmed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), and the molecular weight of the toxin determined to be 6.61 kDa by mass spectrometry. The physiological development of chlorosis in sensitive wheat was investigated using partially purified toxin. Treatment with the toxin had no effect on the greening of etiolated tissue, suggesting that chlorosis results from chlorophyll degradation, rather than inhibition of chlorophyll synthesis. Development of chlorosis was light-dependent, suggesting that it may be a consequence of photochemical bleaching. To test for the involvement of active oxygen (AO) species in photobleaching, toxin-treated tissue was floated in solutions of various AO scavengers. The compound p-benzoquinone, which quenches singlet oxygen and triplet chlorophyll, prevented the development of chlorosis, suggesting that AO species are involved in chlorophyll degradation. High performance liquid chromatography (HPLC) chlorophyll degradation profiles were also consistent with photooxidation. Decreases in carotenoid levels were smaller than and concurrent with the declines in chlorophyll, indicating that toxin-induced chlorosis was not the result of a carotenoid deficiency. It appears that Ptr chlorosis toxin, directly or indirectly, inhibits photosynthesis, leading to chlorophyll photodestruction as illuminated thylakoid membranes become unable to dissipate excitation energy normally used in photosynthesis. en_US
dc.format.extent 4311898 bytes
dc.format.extent 184 bytes
dc.format.mimetype application/pdf
dc.format.mimetype text/plain
dc.language en en_US
dc.language.iso en_US
dc.title Purification and mode of action of PTR, Pyrenophora tritici-repentis, chlorosis toxin en_US
dc.degree.discipline Plant Science en_US
dc.degree.level Master of Science (M.Sc.) en_US


Files in this item

This item appears in the following Collection(s)

Show simple item record

View Statistics