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dc.contributor.authorSonawala, Unnati Subhashen
dc.date.accessioned2021-03-28T06:00:17Zen
dc.date.available2021-03-28T06:00:17Zen
dc.date.issued2019-10-04en
dc.identifier.othervt_gsexam:22361en
dc.identifier.urihttp://hdl.handle.net/10919/102868en
dc.description.abstractHyaloperonospora arabidopsidis (Hpa) is a naturally occurring oomycete pathogen on Arabidopsis thaliana. It is related to downy mildews of economically important crops such as cabbage, kale and broccoli, belonging to the Brassicaceae family. Downy mildew pathogens are obligate biotrophs that extract nutrients exclusively from living plant cells. As a part of its obligate biotrophy lifestyle, Hpa has lost the ability to assimilate inorganic nitrogen and sulfur. It thus has to acquire these nutrients from the host in an organic form; possibly amino acids. Using a reverse genetic approach, I was able to identify two host amino acid transporters that are up-regulated during Hpa infection: AAP3 and AAP6. Both of these transporters are localized in the vasculature of the plant, AAP3 mostly in the root, and AAP6 in the roots and shoots. Using transgenic lines of Arabidopsis containing transcriptional and translational reporter fusion constructs for these genes, I found that AAP3 displays increased mRNA accumulation which is attributable to an increased promoter activity in regions of shoot tissue colonized by Hpa. On the other hand, AAP6 displays a mild increase in mRNA accumulation under Hpa infection, but the induction becomes more prominent at the protein level as seen by fluorescence from GFP fused to AAP6. Surprisingly, null mutants of AAP3 did not impact Hpa growth whereas null mutants of AAP6 made the plant more susceptible to Hpa. Furthermore, aap6 mutants accumulate fewer free amino acids in the phloem compared to wild-type plants when infected with Hpa. Together, these results suggest that AAP6 acts a nutritional starvation gene for the pathogen and hence aids the plant during infection. While we now know more about AAP3's regulation during infection, its function remains to be elucidated. To successfully colonize a plant, a pathogen must be able to achieve both suppression of plant immunity and acquisition of nutrients from the plant host. While the former has been well studied, research on the latter is sparse. This work was a step in the direction to increase our understanding of potential players in nutrient acquisition by pathogens.en
dc.format.mediumETDen
dc.publisherVirginia Techen
dc.rightsThis item is protected by copyright and/or related rights. Some uses of this item may be deemed fair and permitted by law even without permission from the rights holder(s), or the rights holder(s) may have licensed the work for use under certain conditions. For other uses you need to obtain permission from the rights holder(s).en
dc.subjectPlant-pathogen interactionen
dc.subjectamino acid transportersen
dc.subjectnutritional resistanceen
dc.subjectyeast heterologous expressionen
dc.titleUnderstanding the role of host amino acid transporters in nutrient acquisition by oomycete pathogensen
dc.typeDissertationen
dc.contributor.departmentPlant Pathology, Physiology and Weed Scienceen
dc.description.degreeDoctor of Philosophyen
thesis.degree.nameDoctor of Philosophyen
thesis.degree.leveldoctoralen
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen
thesis.degree.disciplinePlant Pathology, Physiology and Weed Scienceen
dc.contributor.committeechairPilot, Guillaumeen
dc.contributor.committeememberTholl, Dorothea Berta Christineen
dc.contributor.committeememberMcDowell, John M.en
dc.contributor.committeememberWestwood, James H.en


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