The recent discovery of PDR1, protein involved in mediating plant symbiosis with fungi, opens new opportunities to manipulate plant yield.
About 80 per cent of terrestrial plants have symbiotic relationship with soil fungi. The fungi provide the plant with water, important nutrients like phosphate and nitrate, and certain trace elements like zinc; the plant, on the other hand, supplies the fungus with carbohydrates. It is assumed that plants were only able to migrate onto land 400 million years ago thanks to this symbiosis.
The formation of this symbiosis is a strictly regulated process that the plant activates in low nutrient levels. The roots release the hormone strigolactone, which is detected by the fungi. The fungal hyphae grow towards the roots, penetrate the epidermis and isolated passage cells, and enter the root cortex. There, the fungal hyphae form tiny branch-like networks, which resemble little trees (arbusculum) and gave the symbiotic relationship its name: vesicular-arbuscular mycorrhizal symbiosis.
Exactly how strigolactones are released into soil from roots and how the fungi find the specialized entry points have now been discovered by team of plant biologist at the University of Zurich (Switzerland) in collaboration with Wageningen (Netherlands). The research group published in Nature (Nat. 7 March 2012) ‘A petunia ABC transporter strigolactone-dependent signalling and branching’ where they demonstrated how strigolactones are released into the soil from the roots and how fungi find the specialized entry points into the soil.
Their results showed that petunia hybrida ABC transporter - PDR1 - is expressed more highly in a low nutrient content in order to attract more symbiotic fungi, which then supply more nutrients. When the researchers used pdr1 mutants, defective in striglocane exudation from roots, resulted in reduced symbiotic interaction. On the other hand, overexpression of PDR1 resulted in increased tolerance to high concentrations of concentrations of a synthetic strigolactone, consistent with increased export of strigolactones from the roots.
In conclusion, PDR1 not only points the way to better harvest but also a new tool for weed control.
You can find the full research paper at: http://www.nature.com.ezproxy.webfeat.lib.ed.ac.uk/nature/journal/vaop/ncurrent/full/nature10873.html
and press release at: