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[Lawrence London <lfljvenaura@gmail.com>]

Researchers make discovery that could increase plant yield in wake of
looming phosphate shortage  |  Peak Oil News and Message Boards
http://peakoil.com/consumption/researchers-make-discovery-that-could-increase-plant-yield-in-wake-of-looming-phosphate-shortage

Researchers make discovery that could increase plant yield in wake of
looming phosphate shortage [image: Consumption]

*UNC-Chapel Hill researchers make discovery that could increase plant yield
in wake of looming phosphate shortage*



*Phosphate is vital for best crop yields, but global supply is limited and
could peak in 30 years.*



(Chapel Hill, N.C. – March 15, 2017) – Scientists at the University of
North Carolina at Chapel Hill have pinpointed a key genetic switch that
helps soil bacteria living on and inside a plant’s roots harvest a vital
nutrient with limited global supply. The nutrient, phosphate, makes it to
the plant’s roots, helping the plant increase its yield.



The work, published in the March 15 issue of *Nature*, raises the
possibility of probiotic, microbe treatments for plants to increase their
efficient use of phosphate. The form of phosphate plants can use is in
danger of reaching its peak – when supply fails to keep up with demand – in
just 30 years, potentially decreasing the rate of crop yield as the world
population continues to climb and global warming stresses crop yields,
which could have damaging effects on the global food supply.



“We show precisely how a key ‘switch protein’,PHR1, controls the response
to low levels of phosphate, a big stress for the plant, and also controls
the plant immune system,” said Jeff Dangl, John N. Couch Distinguished
Professor and Howard Hughes Medical Institute Investigator. “When the plant
is stressed for this important nutrient, it turns down its immune system so
it can focus on harvesting phosphate from the soil. Essentially, the plant
sets its priorities on the cellular level.”



Dangl, who worked with lead authors, postdoctoral researchers Gabriel
Castrillo and Paulo José Pereira Lima Teixeira, graduate student Sur
Herrera Paredes and research analyst Theresa F. Law, found evidence that
soil bacteria can make use of this tradeoff between nutrient-seeking and
immune defense, potentially to help establish symbiotic relationships with
plants. Bacteria seem to enhance this phosphate stress response, in part
simply by competing for phosphate but also by actively ‘telling’ the plant
to turn on its phosphate stress response.



In recent plant biology studies, there have been hints of a relationship
between plant phosphate levels and immune system activity – a relationship
that some microbes can manipulate. In the new study, Dangl and colleagues
delved more deeply into this relationship, using mutant versions of
*Arabidopsis
thaliana*, a weed that has long been the standard “lab rat” of plant
biology research.



In one experiment, Dangl’s team found that *Arabidopsis* plants with mutant
versions of the PHR1 gene not only had impaired phosphate stress responses,
but also developed different communities of microbes in and around their
roots when grown in a local native North Carolina soil. This was the case
even in an environment of plentiful phosphate – where phosphate competition
wouldn’t have been a factor – hinting that something else was happening in
the plants to trigger the growth of different microbial communities. The
researchers found similar results studying PHL1, a protein closely related
to PHR1 with similar but weaker functions.



In another experiment, in lab-dish conditions, the researchers colonized
roots of sterile-grown normal *Arabidopsis* plants with a set of 35
bacterial species isolated from roots of plants grown previously in the
same native soil. In these re-colonized plants, the phosphate stress
response increased when exposed to a low-phosphate condition.



Investigating further, the team showed that PHR1 – and probably to a lesser
extent PHL1 – not only activates the phosphate stress response but also
triggers a pattern of gene expression that reduces immune activity, and
thus makes it easier for resident microbes to survive.



The findings suggest that soil-dwelling microbes have figured out how to
get along with their plant hosts, at least in part by activating PHR1/PHL1
to suppress immune responses to them. Dangl’s team also thinks these
microbes may even be necessary for plants to respond normally to
low-phosphate conditions. It could be possible, then, to harness this
relationship – via probiotic or related crop treatments – to enable plants
to make do with less phosphate.



“Phosphate is a limited resource and we don’t use it very efficiently,”
said Dangl, who is also an adjunct professor of microbiology and immunology
at the UNC School of Medicine. “As part of fertilizer, phosphate runs off
into waterways where it can adversely affect river and marine ecosystems.
It would be better if we could use phosphate in a way that’s more
efficient.”



*Other co-authors were Omri M. Finkel, Piotr Mieczkowski, Corbin D. Jones,
all of UNC-Chapel Hill; former UNC-Chapel Hill postdocs Natalie W.
Breakfield and Meghan E. Feltcher; and Laura de Lorenzo and Javier Paz-Ares
of Spain’s Centro Nacional de Biotecnología.*