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Functional Characterization of Putative Effector Genes of Basil Downy Mildew Pathogen Peronospora belbahrii.

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Title:Functional Characterization of Putative Effector Genes of Basil Downy Mildew Pathogen Peronospora belbahrii.
Authors:Shao, Dandan
Contributors:Tropical Plant Pathology (department)
Keywords:Peronospora belbahrii
pathogen virulence
RXLR effector
Date Issued:May 2017
Publisher:University of Hawaiʻi at Mānoa
Abstract:Peronospora belbahrii, the causal agent of the devastating downy mildew disease on basil, is an
obligate biotrophic oomycete. Similar to other oomycete pathogens, P. belbahrii is believed to
secrete effectors to facilitate host colonization. To this end, we did the functional
characterization of 10 P. belbahrii effector candidate genes, which encode predicted secreted
proteins with a translocation motif RXLR (or RXLR-EER) and/or nuclear localization signals
(NLS). First, we determined their gene expression patterns during infection using reverse
transcription quantitative PCR (RT-qPCR). Five genes were induced during infection and the
functionality of their predicted signal peptides was confirmed using a yeast invertase secretion
system, suggesting that these genes likely encode bona fide effectors that play significant roles in
manipulating host cellular processes to cause disease. Their roles in pathogenicity are currently
being tested through overexpression and host-induced gene silencing (HIGS). To facilitate the
genetic analysis of these and additional effector candidate genes, we developed a transient
expression system in basil for utilizing overexpression and HIGS in a transient manner. To better
analyze the effect resulted from the in planta expression of overexpression and HIGS construct
of PbEC2 on pathogen growth, a quantitative PCR approach was developed to quantify the
pathogen biomass. In addition, we generated transgenic basil to express double-stranded RNAs
of one selected effector gene to determine its function in pathogenicity using HIGS. This study is
expected to facilitate the understanding of P. belbahrii pathogenesis and help develop tools to
control this pathogen.
Description:M.S. Thesis. University of Hawaiʻi at Mānoa 2017.
Rights:All UHM dissertations and theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission from the copyright owner.
Appears in Collections: M.S. - Tropical Plant Pathology

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