AY-­‐WB phytoplasma manipulations of host and non-­‐host leafhopper interactions

Kingdom, Heather (2012) AY-­‐WB phytoplasma manipulations of host and non-­‐host leafhopper interactions. Doctoral thesis, University of East Anglia.

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    Abstract

    Hempitera.
    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.

    Item Type: Thesis (Doctoral)
    Faculty \ School: Faculty of Science > School of Biological Sciences
    Depositing User: Mia Reeves
    Date Deposited: 17 Dec 2012 16:25
    Last Modified: 17 Dec 2012 16:25
    URI: https://ueaeprints.uea.ac.uk/id/eprint/40581
    DOI:

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