Show simple item record

dc.contributor.advisorCulver, James Nen_US
dc.contributor.authorCollum, Tamara Dianeen_US
dc.date.accessioned2016-06-22T05:37:46Z
dc.date.available2016-06-22T05:37:46Z
dc.date.issued2016en_US
dc.identifierhttps://doi.org/10.13016/M20J39
dc.identifier.urihttp://hdl.handle.net/1903/18160
dc.description.abstractVascular phloem loading has long been recognized as an essential step in the establishment of a systemic virus infection. Yet little is known about this process and the mechanisms that control it. In this study, an interaction between the replication protein of Tobacco mosaic virus (TMV) and phloem specific auxin/indole acetic acid (Aux/IAA) transcriptional regulators was found to modulate virus phloem loading. Promoter expression studies show TMV 126/183 kDa interacting Aux/IAAs predominantly express and accumulate within the nuclei of phloem companion cells (CC). Furthermore, CC Aux/IAA nuclear localization is disrupted upon infection with an interacting virus but not during infection with a non-interacting virus. In situ analysis of virus spread shows the inability of TMV variants to disrupt Aux/IAA CC nuclear localization correlates with a reduced ability to load into the vascular tissue. Subsequent systemic movement assays also demonstrate that a virus capable of disrupting Aux/IAA localization is significantly more competitive at systemic movement than a non-interacting virus. Similarly, CC expression and over-accumulation of a degradation-resistant-interacting Aux/IAA protein was found to selectively inhibit TMV accumulation and phloem loading. Transcriptional expression studies demonstrate a role for interacting Aux/IAA proteins in the regulation of salicylic acid and jasmonic acid dependent host defense responses as well as virus specific movement factors including pectin methylesterase that are involved in regulating plasmodesmata size exclusion limits and promoting virus cell-to-cell movement. Further characterization of the phloem environment was done using two phloem specific promoters (pSUC2 and pSULTR2;2) to generate epitope-tagged polysomal-RNA complexes. Immuno-purification using the epitope tag allowed us to obtain mRNAs bound to polysomes (the translatome) specifically in phloem tissue. We found the phloem translatome is uniquely altered during TMV infection with 90% and 88% of genes down regulated in the pSUC2 and pSULTR2;2 phloem translatomes, compared to 31% of genes down regulated in the whole plant p35S translatome. Transcripts down regulated in phloem include genes involved in callose deposition at plasmodesmata, host defense responses, and RNA silencing. Combined, these findings indicate TMV reprograms gene expression within the vascular phloem as a means to enhance phloem loading and systemic spread.en_US
dc.language.isoenen_US
dc.titleCHARACTERIZATION OF TOBACCO MOSAIC VIRUS DIRECTED REPROGRAMMING OF PHLOEM GENE EXPRESSION TO PROMOTE VIRAL PHLOEM LOADING AND SYSTMEIC MOVEMENTen_US
dc.typeDissertationen_US
dc.contributor.publisherDigital Repository at the University of Marylanden_US
dc.contributor.publisherUniversity of Maryland (College Park, Md.)en_US
dc.contributor.departmentCell Biology & Molecular Geneticsen_US
dc.subject.pqcontrolledVirologyen_US
dc.subject.pqcontrolledPlant sciencesen_US
dc.subject.pqcontrolledCellular biologyen_US
dc.subject.pquncontrolledAuxinen_US
dc.subject.pquncontrolledPathogen Defenseen_US
dc.subject.pquncontrolledPhloem Loadingen_US
dc.subject.pquncontrolledPlant Hormone Signalingen_US
dc.subject.pquncontrolledSalicyclic Aciden_US
dc.subject.pquncontrolledVirus Movementen_US


Files in this item

Thumbnail
Thumbnail
Thumbnail
Thumbnail

This item appears in the following Collection(s)

Show simple item record