Condensed tannins as in vivo antioxidants in Populus tremula x tremuloides

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dc.contributor.authorGourlay, Geraldine
dc.contributor.supervisorConstabel, Carsten Peter
dc.contributor.supervisorHawkins, Barbara J.
dc.date.accessioned2019-12-24T19:32:48Z
dc.date.copyright2019en_US
dc.date.issued2019-12-24
dc.degree.departmentDepartment of Biology
dc.degree.levelDoctor of Philosophy Ph.D.en_US
dc.description.abstractPlants are exposed to diverse environmental stresses, which can lead to the accumulation of harmful reactive oxygen species (ROS). To prevent cellular damage, plants have evolved diverse antioxidant compounds and mechanisms to scavenge and remove ROS. My research aimed to determine if condensed tannins (CTs) function as in vivo antioxidants in plants. CTs are abundant plant secondary metabolites and are well-known for their strong in vitro antioxidant activity, but their function as antioxidants in planta has not previously been investigated. I used transgenic hybrid poplar (Populus tremula x tremuloides) with high (MYB134- and MYB115-overexpressing) and low (MYB134-RNAi) leaf CT content. Three different abiotic stresses were used to induce oxidative stress in the plants: methyl viologen (MV), drought, or UV-B stress. Oxidative stress can damage the plant's photosystems, and this damage was assessed using chlorophyll fluorescence. I employed light-adapted (Fq’/Fm’) and dark-adapted (Fv/Fm) parameters of chlorophyll fluorescence and monitored photosystem II function during each stress. Under all three stresses, the high-CT transgenics retained greater chlorophyll fluorescence, demonstrating reduced photosystem II damage, compared to wild-type plants. Oxidative damage was measured by quantifying malondialdehyde (MDA), and hydrogen peroxide (H2O2) was quantified as a measure of ROS accumulation. High-CT plants consistently accumulated less H2O2 and MDA than wild-type plants before and after each stress. MYB134-RNAi plants showed the converse effects, as predicted by lower CT concentrations, with reduced photosystem function and increased levels of H2O2 and MDA compared to wild-type following each stress. Overall, this work demonstrates that CTs can function as in planta antioxidants and can aid in protection against oxidative damage. My work provides the first evidence for an antioxidant function of CTs in living plants exposed to stress.en_US
dc.description.embargo2020-12-18
dc.description.scholarlevelGraduateen_US
dc.identifier.bibliographicCitationGourlay G, Constabel CP. 2019. Condensed tannins are inducible antioxidants and protect hybrid poplar against oxidative stress. Tree Physiology 39, 345–355.en_US
dc.identifier.urihttp://hdl.handle.net/1828/11431
dc.languageEnglisheng
dc.language.isoenen_US
dc.rightsAvailable to the World Wide Weben_US
dc.subjectcondensed tanninsen_US
dc.subjectantioxidantsen_US
dc.subjectpoplaren_US
dc.subjectstressen_US
dc.titleCondensed tannins as in vivo antioxidants in Populus tremula x tremuloidesen_US
dc.typeThesisen_US

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