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Seminar: Effectors of Candidatus Phytoplasma: Proteins that Alter Development and Immunity in Plants

Juan Francisco Iturralde Martinez, M.S. student, Department of Plant Pathology and Environmental Microbiology, Penn State
Image: Michael Houtz, Penn State

Image: Michael Houtz, Penn State

Date and Location

When (Date/Time)

September 29, 2017, 12:20 PM - 1:10 PM

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Abstract

Candidatus Phytoplasma are wall-less pleomorphic bacteria known to cause peculiar symptoms in sets of different crops which can often be fatal and incur big losses. They belong to the Phylum Tenericutes (“tender skin”) alongside Mycoplasma, Ureaplasma, and Spiroplasma. Their origin is related to high GC% Gram (+) that lost their cell wall and reduced their genome size to contain only a very basic set of genes with a poor %GC composition.

These bacteria usually live in the cytosol of their host cells and are phloem limited. They are heavily dependent on their host metabolism to carry out their own functions and lack any kind of developed secretion system, only relying on a basic SecA. Classification is often made based on their 16S rRNA gene, however some more details are provided and the system has shown some flaws.

Typical symptoms include virescence, in which non-green plant organs turn green; and phyllody, in which a hormonal disequilibrium induces the appearance of leaves in flowers or fruits, as well as an uncontrolled proliferation of secondary growth known as witches’ broom. Nonetheless, the most important symptom is an overall yellowing, probably caused by changes in the carbohydrate synthesis.

Transmission is persistent, in a circulative propagative fashion in their host vectors that include species of leafhoppers, psyllid, and planthoppers.

The SecA mechanism is responsible for the secretion of effectors, proteins that change plant metabolism and immune response to favor the colonization of their tissue by Candidatus Phytoplasma and manipulate insect behavior to be spread to new hosts.

This seminar will cover the molecular changes that effectors produce in hosts and the laboratory and bioinformatics approaches to study and characterize such successful modulators of development.

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814-867-5372