Columbia, Missouri
October 23, 2008
Without eyes or ears, plants must
rely on the interaction of molecules to determine appropriate
mating partners and avoid inbreeding. In a new study,
University of Missouri
researchers have identified pollen proteins that may contribute
to the signaling processes that determine if a plant accepts or
rejects individual pollen grains for reproduction.
Like humans, the mating game isn’t always easy for plants.
Plants rely on external factors such as wind and animals to
bring them potential mates in the form of pollen grains. When
pollen grains arrive, an introduction occurs through a
“conversation” between the pollen (the male part of the flower)
and the pistil (the female part of the flower). In this
conversation, molecules take the place of words and allow the
pollen to identify itself to the pistil. Listening in on this
molecular conversation may provide ways to control the spread of
transgenes from genetically-modified crops to wild relatives,
offer better ways to control fertilization between cross
species, and lead to a more efficient way of growing fruit
trees.
“Unlike an animal’s visual cues about mate selection, a plant’s
mate recognition takes place on a molecular level,” said Bruce
McClure, associate director of the Christopher S. Bond Life
Sciences Center and researcher in the MU Interdisciplinary Plant
Group and Division of Biochemistry. “The pollen must, in some
way, announce to the pistil its identity, and the pistil must
interpret this identity. To do this, proteins from the pollen
and proteins from the pistil interact; this determines the
acceptance or rejection of individual pollen grains.”
In the study, researchers used two specific pistil proteins,
NaTTS and 120K, as “bait” to see what pollen proteins would bind
to them. These two pistil proteins were used because they
directly influence the growth of pollen down the pistil to the
ovary where fertilization takes place.
Three proteins, S-RNase-binding protein (SBP1), the protein
NaPCCP and an enzyme, bound to the pistil proteins. This action
suggests that these proteins likely contribute to the signaling
processes that affect the success of pollen growth.
“Our experiment was like putting one side of a Velcro strip on
two pistil proteins and then screening a collection of pollen
proteins to see which of the pollen proteins have the
complementary Velcro strip for binding,” McClure said. “If it
sticks, it’s a good indication that the pollen proteins work
with the pistil proteins to determine the success of
reproduction.”
In previous studies, McClure showed that S-RNase, a protein on
the pistil side, caused rejection of pollen from close relatives
by acting as a cytotoxin, or a toxic substance, in the pollen
tube.
For their study, the MU team used Nicotiana alata, a relative of
tobacco commonly grown in home gardens as “flowering tobacco.”
The study, “Pollen Proteins Bind to the C-Terminal Domain of
Nicotiana Alata Pistil Arabinogalactan Proteins,” was published
in the Journal of Biological Chemistry and was co-authored by
McClure; Kirby N. Swatek, biochemistry graduate student; and
Christopher B. Lee, post-doctoral researcher at the Bond Life
Sciences Center.
Faculty from six of MU’s colleges and schools perform
interdisciplinary research in the Christopher S. Bond Life
Sciences Center with a vision to become a recognized world-wide
center of scientific excellence and leadership in life sciences
research, innovation and education. The Center integrates the
strengths of multiple, often disparate, disciplines to promote
discovery that boosts the production and quality of food,
improves human and animal health and enhances environmental
quality. The Center enriches the state of Missouri and its
people by generating new businesses and jobs, fueling the
economy through the creation and dissemination of new knowledge,
and training young people to solve complex interdisciplinary
problems. |
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