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Title: AY-WB phytoplasma manipulations of host and non-host leafhopper interactions
Author: Kingdom, Heather
ISNI:       0000 0004 2736 0719
Awarding Body: University of East Anglia
Current Institution: University of East Anglia
Date of Award: 2012
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In plant hosts, phytoplasmas induce physiological changes and in both hosts modulate plant-insect interactions. Previously, interactions have been examined with both hosts infected with phytoplasmas. Thus, it is unclear which organism the effect stems from or how phytoplasmas facilitate changes. To investigate phytoplasma manipulations of insect-plant interactions, the model Arabidopsis thaliana was used together with the fully sequenced Aster Yellows phytoplasma strain Witches’ Broom (AY-WB) and vector leafhopper Macrosteles quadrilineatus. I demonstrate possibility to differentiate effects of phytoplasma infection within plant and within insect hosts. To assess root cause of changes, AY-WB secreted effector proteins were examined, their roles within plants, and in manipulations of vector fecundity. One of the 56 secreted AY-WB proteins (SAPs) identified, SAP11, carries a nuclear localization signal and accumulates in plant cell nuclei (Bai et al. 2009). SAP11 is shown to reduce production of plant defense hormone jasmonic acid (Sugio et al. 2011). Stable expression of SAP11 and 3 other SAPs in Arabidopsis increase fecundity of M. quadrilineatus. In addition, phytoplasmas are known to affect non-host insect-plant interactions. Using the same approach, I demonstrate D. maidis survives and produces nymphs only on AY-WB-infected Arabidopsis. Furthermore, I show that whilst SAP11 has no effect on D. maidis survival, 3 other SAPs increase D. maidis survival and oviposition. These data suggest phytoplasmas utilize a suite of effector proteins to manipulate both host and non-host insect-plant interactions. Thus, AY-WB effector functions extend beyond direct interaction with plant hosts; they stimulate generation of insect vectors, and increase chance of uptake by novel insect hosts. This project highlights the value of using a model system in studying phytoplasma manipulation of their hosts and gives insight into development of evolutionary associations between phytoplasmas and vectors.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available