Geminiviruses Provide Insights Into Plant Host Biology
Author | : Aaron Nicholas Bruns |
Publisher | : |
Total Pages | : |
Release | : 2019 |
Genre | : Biochemistry |
ISBN | : |
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Geminiviruses and their interactions with plant hosts provide a wealth of insights into the biology of plant defenses. SNF1-related kinase 1 (SnRK1) has long been known to condition tolerance to these viruses, but the mechanism behind this remained elusive. In this thesis I present evidence that the antiviral properties of SnRK1 can at least in part be attributed to phosphorylation of the mRNA cap-binding protein eukaryotic initiation factor 4E (eIF4E) and its plant-specific homolog eIFiso4E. We have obtained evidence that these proteins interact, that SnRK1 can phosphorylate eIFiso4E, and that phosphorylation results in translation inhibition both in a complemented yeast system and in plant cells. Geminivirus biology has also afforded us the opportunity to isolate and characterize individual non-coding transcripts from the plant specific RNA polymerases IV and V due to the immense number of these transcripts produced in an infected cell. These enzymes are key players in an epigenetic host defense that results in methylation and silencing of geminivirus chromatin. Using circular RT-PCR focused on the intergenic region of a geminivirus, we have been able to accurately map the ends of transcripts derived from these polymerases for the first time. Finally, I have demonstrated that geminivirus pathogenicity factors inhibit production of ethylene, a gaseous plant hormone. Because ethylene signaling functions in pathogen defense, this observation allows us to further explore host and virus defense counter-defense interplay.