permaculture

[Jacqueline Greenleaf <jacque@book-woman.net>]

> On Apr 24, 2017, at 4:08 PM, Lawrence London <lfljvenaura@gmail.com> wrote:
> 
> Researchers make discovery that could increase plant yield in wake of
> looming phosphate shortage.
> https://phys.org/news/2017-03-discovery-yield-looming-phosph.html#nRlv
> 
> 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
> <https://phys.org/tags/plants/> to increase their efficient use of phosphate
> <https://phys.org/tags/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 as
> the world population continues to climb and global warming stresses crop
> yields, which could have damaging effects on the global food supply
> <https://phys.org/tags/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 <https://phys.org/tags/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
> <https://phys.org/tags/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."
> 
> 
> Read more at:
> https://phys.org/news/2017-03-discovery-yield-looming-phosph.html#jCp
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