West Lafayette, Indiana
March 26, 2007
An international team of
researchers has discovered that two types of plant proteins are
at work in the transport of an important growth hormone, a
finding that could have applications in creating plants with
specific characteristics.
Previously thought to function
independently, the two types of proteins were shown to comprise
mechanisms that work both cooperatively and synergistically,
depending upon their location in the plant. Together they
control the movement of auxin, a hormone that, among other
functions, regulates plant architecture, tissue development and
flowering time.
The documentation of how these two mechanisms work together has
direct applications in designing crops suitable for biofuel and
ethanol production or for creating ornamentals with certain
desirable traits, like developing more flowers.
"This is a major step in understanding auxin transport, which is
vital to every aspect of plant growth and development," said
Angus Murphy, the professor of horticulture and landscape
architecture at Purdue University
who led the team.
Murphy said results of the study, published last month in
The Plant Cell, have
already been applied and have been used to create plants with
larger root structures.
"This study gives us another important tool in our toolbox," he
said. "Before, we would modify plants one gene at a time, but
now we realize why this approach has not worked very well. We
now see that there are two elements of control to keep in mind,
just as amplified sound is best controlled by modulating gain
from the microphone and amplifier output to the speakers."
A first way in which the finding could be directly applied would
be in developing crops with more usable biomass for the
production of ethanol or other biofuels, which are renewable
fuels derived from recently-living organisms like plants.
Reengineering the complex cellular machinery of plants to
increase biofuel yields requires alterations of their cell
walls, which provide plants with much of their strength and
rigidity. Altered plant architecture can help compensate for
this weakness and enhance the production of tissue most suitable
for biofuel feedstocks.
"Scientists will be able to use information from this study to
better manipulate plant architecture using a combinatorial
approach," Murphy said. "If you want more productive materials
for biofuel production, architectural changes will be required
to make it work. For example, when plastic body panels were
invented for cars, they couldn't just replace the steel. The
designers had to change the manner in which the panels were
supported and attached to the frame. That is similar to how we
have to think about the effects that modifications will have on
the plant as a whole."
These transport proteins lie in a plant cell's exterior membrane
where they coordinate movement of different substances into and
out of the cell. Murphy's team found that the two transport
proteins, called PINs and PGPs, work on their own or
interactively depending upon the plant tissue involved. Multiple
types of each protein also often work together in specific,
tissue-dependent ways.
In the model plant Arabidopsis, there are eight PIN proteins and
21 PGPs. This provides nearly endless pairings to control the
transport of auxin throughout the plants' various tissues,
Murphy said.
The research also should have important implications in
horticulture.
For example, the team's findings might be used to produce
ornamentals that do not need pruning or that have larger root
systems to support more vegetation, he said. Such plants would
require less labor, energy and - with larger roots - less
fertilizer, Murphy said.
The team's findings could have applications in food crops, but
Murphy said he hasn't pursued such work due to some concerns
over eating genetically modified foods.
"We're focusing on biofuels and ornamentals because everybody
loves to drive their car, and people don't eat their flowers,"
he said.
Murphy's research was funded by the National Science Foundation,
U.S. Department of Agriculture, U.S. Department of Energy, and
the Biotechnology and Biological Research Council of the United
Kingdom. Cooperating educational facilities include the
University of Tubingen, Germany; The Basel-Zurich Plant Science
Center at the University of Zurich, Switzerland; and the RIKEN
Plant Science Center in Kanagawa, Japan. Murphy continues to
study auxin transport as well as the role and importance of
individual PIN and PGP protein pairings.
ABSTRACT
Interactions among PIN-FORMED and
P-Glycoprotein Auxin Transporters in Arabidopsis[W]
Joshua J. Blakesleea, Anindita Bandyopadhyaya, Ok Ran Leea,
Jozef Mravecb, Boosaree Titapiwatanakuna, Michael Sauerb,
Srinivas N. Makama, Yan Chenga, Rodolphe Bouchardc, Jii Adamecd,
Markus Geislerc, Akitomo Nagashimae, Tatsuya Sakaie, Enrico
Martinoiac, Jii Frimlb, Wendy Ann Peera and Angus S. Murphy
Directional transport of the phytohormone auxin is established
primarily at the point of cellular efflux and is required for
the establishment and maintenance of plant polarity. Studies in
whole plants and heterologous systems indicate that PIN-FORMED
(PIN) and P-glycoprotein (PGP) transport proteins mediate the
cellular efflux of natural and synthetic auxins. However,
aromatic anion transport resulting from PGP and PIN expression
in nonplant systems was also found to lack the high level of
substrate specificity seen in planta. Furthermore, previous
reports that PGP19 stabilizes PIN1 on the plasma membrane
suggested that PIN-PGP interactions might regulate polar auxin
efflux. Here, we show that PGP1 and PGP19 colocalized with PIN1
in the shoot apex in Arabidopsis thaliana and with PIN1 and PIN2
in root tissues. Specific PGP-PIN interactions were seen in
yeast two-hybrid and coimmunoprecipitation assays. PIN-PGP
interactions appeared to enhance transport activity and, to a
greater extent, substrate/inhibitor specificities when
coexpressed in heterologous systems. By contrast, no
interactions between PGPs and the AUXIN1 influx carrier were
observed. Phenotypes of pin and pgp mutants suggest discrete
functional roles in auxin transport, but pin pgp mutants
exhibited phenotypes that are both additive and synergistic.
These results suggest that PINs and PGPs characterize
coordinated, independent auxin transport mechanisms but also
function interactively in a tissue-specific manner.
Source:
Fundación Antama
Descubren
un método para regular la arquitectura de la planta, su
desarrollo y floración
El trabajo científico ha sido desarrollado en Estados Unidos y
gracias a él se pueden diseñar plantas para biocombustibles y
flores ornamentales con características especiales
Un equipo de investigadores de la Universidad de Purdue
(Indiana, Estados Unidos) ha descubierto dos tipos de proteínas
de plantas que se ocupan del transporte de una importante
hormona del crecimiento, la oxina. Este descubrimiento podría
tener aplicaciones en la creación de plantas con características
específicas, ya que esta hormona regula la arquitectura de la
planta, desarrollo y floración.
El modo en que estos dos mecanismos trabajan conjuntamente tiene
aplicaciones directas en el diseño de cultivos destinados a la
producción de biocombustibles y etanol, o para crear plantas
ornamentales con características específicamente deseadas, tales
como la aparición de mayor número de flores, según recoge la
lista de distribución de noticias Agbioworld.
El profesor de Horticultura y Arquitectura del Paisaje de la
Universidad de Purdue, Angus Murphy, quien ha liderado el
proyecto de investigación, asegura que “este es el paso más
grande que se ha dado para comprender el transporte de la oxina,
que resulta vital para todos los aspectos del crecimiento y
desarrollo de la planta”. Además, destaca que los resultados del
estudio, publicado el mes pasado, han sido aplicados y se han
empleado para crear plantas con estructuras de raíz más grandes.
Este descubrimiento puede aplicarse directamente en el
desarrollo de cultivos que produzcan mayor cantidad de biomasa
para la producción de etanol u otros biocombustibles, que son
renovables y derivados de organismos como las plantas. La
reconstrucción de la compleja maquinaria celular de las plantas
para incrementar las producciones de biocombustible requiere
alteraciones de las paredes celulares, que dotan a la planta de
su fuerza y rigidez. La alteración de la arquitectura de la
planta puede ayudar a compensar su debilidad, y mejorar la
producción de tejido más adecuado para biocombustibles.
“Los científicos podrán emplear la información de este estudio
para modificar mejor la estructura de la planta, a través de un
acercamiento combinatorio”, dijo Murphy. “Si se quieren
materiales más productivos para la producción de
biocombustibles, los cambios estructurales en la planta serán
necesarios. Por ejemplo, cuando se inventaron los paneles de
plástico para los coches, no podían desplazar al acero. Los
diseñadores tuvieron que modificar el modo en que los paneles se
ajustaban a la estructura. Esto es similar a cómo tenemos que
pensar en los efectos que las modificaciones de las plantas
pueden implicar”, explica el científico.
Las dos proteínas transportadoras permanecen en una membrana
exterior de la célula de la planta, donde coordinan el
movimiento de diversas sustancias dentro y fuera de la célula.
El equipo de Murphy descubrió que ambas actúan por su cuenta o
de manera interactiva, dependiendo del tejido implicado.
Más información:
www.agbioworld.org |
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In
this amplified image of a root
tip, an imaging technique shows
the two types of proteins that
Murphy's team has described,
which can work independently or
cooperatively. The PGP proteins
are red, the PIN proteins are
green, and where they both occur
and work together, the image
appears yellow. These proteins
can be altered to produce plants
with bigger roots. |
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