THE PHYTOHORMONE ETHYLENE: (I) INVESTIGATING THE MOLECULAR FUNCTION OF RTE1 AND (II) INSIGHTS ON THE EVOLUTION OF THE ETHYLENE BIOSYNTHESIS AND SIGNALING PATHWAYS

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dc.contributor.advisorChang, Carenen_US
dc.contributor.authorClay, Johnen_US
dc.contributor.departmentCell Biology & Molecular Geneticsen_US
dc.contributor.publisherDigital Repository at the University of Marylanden_US
dc.contributor.publisherUniversity of Maryland (College Park, Md.)en_US
dc.date.accessioned2018-07-17T05:37:03Z
dc.date.available2018-07-17T05:37:03Z
dc.date.issued2017en_US
dc.description.abstractEthylene is an important phytohormone that regulates growth, development and stress responses in land plants and charophycean green algae. In Arabidopsis thaliana, ethylene is perceived by a family of five receptors. One of these five receptors, ETR1, is dependent on REVERSION-TO-ETHYLENE1 (RTE1) and Cytochrome B5 (Cb5) while the other four receptors are not. We found that RTE1 and Cb5 interact in planta and used genetic analyses to place Cb5 upstream of RTE1 in the ethylene signaling pathway. After comparing different ethylene receptors we identified an N-terminally localized proline that is important in determining whether a receptor is RTE1-dependent. Our results suggest that Cb5 receives electrons from upstream redox molecules, passes these electrons to RTE1; RTE1 is then able to activate the ETR1 receptor possibly by acting a molecular chaperone that refolds the ETR1 receptor into an active conformation. The ethylene signal transduction pathway is functionally conserved in the charophycean green algae such as Spirogyra pratensis, suggesting that this signaling pathway was present in the common ancestor of charophytes and land plants over 450 million years ago. However, it is unclear whether the central regulator of ethylene response, EIN2, was conserved in charophytes. Furthermore, the details of ethylene biosynthesis in charophytes were unresolved. After examining the genomes and transcriptomes of many green algae we are able to report that EIN2 is conserved in most charophytes and even some of the more distantly related chlorophycean green algae. Moreover, the Spirogyra EIN2 is functionally conserved and able to activate ethylene responses in Arabidopsis. Ethylene is synthesized via a two-step reaction involving the conversion of S-adenosyl-L-methionine (SAM) to 1-aminocyclopropane-1-carboxylic acid (ACC) by the enzyme ACC synthase (ACS), followed by oxidation of ACC to ethylene gas by the enzyme ACC oxidase (ACO). We identified S. pratensis ACS homologs and demonstrated that S. pratensis can synthesize ACC. S. pratensis lacks ACO homologs but we find it is still capable of producing low levels of ethylene. From our results we conclude that the ethylene biosynthesis and signaling pathways were established in early charophytes allowing these algae to establish ethylene as an important signalling molecule.en_US
dc.identifierhttps://doi.org/10.13016/M22B8VF98
dc.identifier.urihttp://hdl.handle.net/1903/20772
dc.language.isoenen_US
dc.subject.pqcontrolledMolecular biologyen_US
dc.subject.pqcontrolledBioinformaticsen_US
dc.subject.pqcontrolledCellular biologyen_US
dc.subject.pquncontrolledACCen_US
dc.subject.pquncontrolledalgaeen_US
dc.subject.pquncontrolledEIN2en_US
dc.subject.pquncontrolledEthyleneen_US
dc.subject.pquncontrolledRTE1en_US
dc.subject.pquncontrolledSpirogyraen_US
dc.titleTHE PHYTOHORMONE ETHYLENE: (I) INVESTIGATING THE MOLECULAR FUNCTION OF RTE1 AND (II) INSIGHTS ON THE EVOLUTION OF THE ETHYLENE BIOSYNTHESIS AND SIGNALING PATHWAYSen_US
dc.typeDissertationen_US

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