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Saturday, May 26, 2012
Phosphorus Poor Soils
This research has uncovered the phosphorus up take pathways used in
soils with scant phosphorous. It can be used in the future to ensure
superior up take in hungry soils. This may seem like unnecessary
fine tuning the plants and that may well be true. We are all used to
adding the short fall back in. Yet this is a nice option to have
Once biochar becomes widely adopted, there well be far less nutrient
deficiency to deal with but we will also working with far more
depleted soils, particularly in the tropics. Thus this could well be
It is all good.
When the soil holds
not enough phosphorus
by Staff Writers
(SPX) May 21, 2012
This is an image,
obtained by confocal microscopy, of a root of the tiny mustard-like
plant Arabidopsis thaliana, showing (in green) the localization of
the newly identified phosphate transporter, on the membranes
(outlines) of the root cells. Credit: Estelle Remy, Instituto
Gulbenkian de Ciencia, Portugal, 2012.
Plants cannot survive
without phosphorus. It forms the backbone of many crucial molecules
(such as DNA) and is a key player in energy transfer reactions. Low
availability of phosphorus is a major environmental stress for plants
and can lead to great losses in crop production.
But plants can't make
their own phosphorus; they get all they need at the root-soil
interface, in the form of inorganic phosphate (Pi), so one way to
maximise the amount of phosphorus in the plant is to turn up Pi
uptake by root cells.
Paula Duque and her
research team at the Instituto Gulbenkian de Ciencia (Lisbon) have
identified a new Pi transporter in the root cells of the tiny mustard
plant Arabidopsis thaliana that acts, crucially, when Pi is scarce.
Their findings, published online in the journal New Phytologist,
provide insight into how phosphate transport systems may be
manipulated in plants to counteract stressful conditions and thus,
potentially, lead to improved crop yields.
The transporter the
IGC researchers work with is a protein located on the membranes of
root cells, which is consistent with it playing a role in the uptake
of phosphorus from the soil.
Showing its location
in the plant was the first step in a detailed study of when and how
the transporter acts. The researchers went on to isolate two
Arabidopsis thaliana mutants, both of which are unable to produce the
They found that,
although mutants and wild-type plants grow equally well in the
presence of standard amounts of Pi, things look quite different when
Pi becomes scarce: the mutant plants (that do not have a
functional transporter) display smaller seedlings, smaller primary
roots and overdeveloped secondary roots - characteristic features of
plants suffering from phosphorus deprivation.
Estelle Remy, a
post-doc in the laboratory, describes the experiments, "The
effects were completely reversed when we re-introduced the
'corrected' gene for the transporter into mutant plants.
This is a strong
indication that it is indeed lack of the transporter that underlies
increased sensitivity to low Pi. Furthermore, by forcing plants to
produce more of the transporter than usual, we made them more
tolerant to low Pi - which further supports a role in phosphorus
uptake under these conditions."
Says Paula Duque, "In
collaboration with Isabel Sa-Correia's group at the Instituto
Superior Tecnico, we used yeast cells that carry the plant
transporter to prove that this transporter chemically binds Pi
"We are thus
confident that we have proven, unequivocally, that the Pht1;9
transporter mediates Pi uptake when Arabidopsis experiences
phosphorus starvation. Its role in plants makes perfect sense: we
know that plants respond to limited Pi by switching on and/or off a
series of genes that lead, ultimately, to a balanced distribution of
phosphorus in the plant.
"One of the
processes entails triggering the production of membrane transporters.
We now know that Pht1:9 (our transporter) is one of them, making it a
potential target for manipulating crops that may be under
environmental stress due to low phosphorus availability".
This study was carried
out in collaboration with the Institute for Biotechnology and
BioEngineering at the Instituto Superior Tecnico (Lisbon). It was
funded by the Fundacao para a Ciencia e a Tecnologia (Portugal).