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Full text release has been delayed at the author's request until December 17, 2028

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The use of geminivirus to model host regulation and development pathways

Regedanz, Elizabeth
http://orcid.org/0009-0008-4243-6861
http://rave.ohiolink.edu/etdc/view?acc_num=osu1691849719905209

Abstract Details

2023, Doctor of Philosophy, Ohio State University, Molecular Genetics.
Geminiviruses infect a wide variety of plants and encode very few viral genes. As such, they rely heavily upon host machinery to drive their replication and hijack host pathways to ensure a productive infection. In geminiviruses belonging to the genus Begomovirus, coat protein (CP) expression depends on viral AL2 protein, which derepresses and activates the CP promoter through sequence elements within the viral intergenic region (IR). However, AL2 does not exhibit sequence-specific DNA binding activity but instead is directed to responsive promoters through interactions with host factors, most likely transcriptional activators or repressors. In the main chapter of this dissertation, we describe a plant-specific transcription factor, Arabidopsis thaliana TCP24 (AtTCP24), that interacts with AL2 and recognizes a class II TCP binding site in the CP promoter (GTGGTCCC). This motif corresponds to the previously identified conserved late element (CLE). We also report that histone 3 lysine 27 trimethylation (H3K27me3), an epigenetic mark associated with facultative repression, is enriched over the viral IR. H3K27me3 is deposited by Polycomb repressive complex 2 (PRC2), a critical regulator of gene expression and development in plants and animals. Remarkably, CLE mutation in Tomato golden mosaic virus (TGMV) and Cabbage leaf curl virus (CaLCuV) CP promoters greatly diminishes H3K27me3 levels on viral chromatin and causes a dramatic delay and attenuation of disease symptoms in infected Arabidopsis and Nicotiana benthamiana plants. Symptom remission is accompanied by decreased viral DNA levels in systemically infected tissue. Nevertheless, in transient replication assays CLE mutation delays but does not limit the accumulation of viral double-stranded DNA, although single-stranded DNA and CP mRNA levels are decreased. These findings suggest a model where TCP24 binds the CLE early in infection and directly or indirectly recruits PRC2, resulting in CP promoter repression. When CP is required late in infection, TCP24:AL2 interaction recruits AL2 to derepress and activate the promoter. Thus, a repressive host transcription factor is repurposed to target a viral factor essential for promoter activity. The presence of the CLE in many begomoviruses suggests a common scheme for late promoter regulation. We further show in Appendix A that there is overlap between anti-viral defense and transposon suppression as we found that recovery from geminivirus infection leads to hyper suppression of host transposable element DNA. Finally, we document in Appendix B the characterization of a host chromatin reader that recognizes a mark of active gene transcription, histone 3 lysine 36 trimethylation, and is involved in antiviral defense. Loss of this reader leads to severe infection symptoms, suggesting a pathway that can target active viral genomes as a secondary means to combat the infection.
David Bisaro (Advisor)
146 p.
Molecular Biology; Virology
geminivirus; PRC2; epigenetics

Recommended Citations

Citations

  • Regedanz, E. (2023). The use of geminivirus to model host regulation and development pathways [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1691849719905209

    APA Style (7th edition)

  • Regedanz, Elizabeth. The use of geminivirus to model host regulation and development pathways. 2023. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1691849719905209.

    MLA Style (8th edition)

  • Regedanz, Elizabeth. "The use of geminivirus to model host regulation and development pathways." Doctoral dissertation, Ohio State University, 2023. http://rave.ohiolink.edu/etdc/view?acc_num=osu1691849719905209

    Chicago Manual of Style (17th edition)

osu1691849719905209
© 2023, all rights reserved.
This open access ETD is published by The Ohio State University and OhioLINK.