Date: June 16, 2020 Source:
University of Copenhagen
Summary:
Researchers from the University
of Copenhagen have discovered an important gene in plants that could help
agricultural crops collaborate better with underground fungi -- providing them
with wider root networks and helping them to absorb phosphorus. The discovery
has the potential to increase agricultural efficiency and benefit the
environment.
It is estimated that about 70
percent of phosphorus fertilizer used in Danish agriculture accumulates in soil,
whereas only 30 percent of it reaches plants.
Quid pro quo -- that's how one
might describe the "food community" that the majority of plants have with
mycorrhizal fungi. Plants allow fungi to live among their roots, while feeding
them fat and sugar. And in return, fungi use their far-reaching hypha
(filamentous branches) to capture vital soil nutrients for plants, including the
important mineral phosphorus.
Now, researchers at the
University of Copenhagen's Department of Plant and Environmental Sciences have
discovered an extraordinary plant gene, the CLE53 gene, which regulates
cooperation between fungi and plants. The gene is central to a mechanism that
controls how receptive plants are to working with mycorrhizal fungi. Down the
road, this newfound knowledge could serve to deliver better harvests and reduced
fertiliser use.
"Similar genes are found in all
plants -- including agricultural crops. So, by mutating or turning off the CLE53
gene in a crop plant, it is more likely for a plant to become symbiotically
involved with a fungus. In doing so, it becomes possible to reduce the need for
phosphorus fertilizers, as plants improve at absorbing preexistent phosphorus
from soil," explains Assistant Professor Thomas Christian de Bang of the
Department of Plant and Environmental Sciences. The research has been published
in the Journal of Experimental Botany.
Seventy percent of phosphorus
fertilization does not reach plants
Phosphorus is vital for all
plants. However, the problem with phosphorus use in agriculture is that more of
it is applied for fertilisation than can be absorbed by crops. It is estimated
that about 70 percent of phosphorus fertilizer used in Danish agriculture
accumulates in soil, whereas only 30 percent of it reaches plants. With rain,
there is an ever present risk that some of the accumulated phosphorus will be
discharged into streams, lakes and the sea.
Paradoxically, researchers have
observed that when phosphorus levels in soil are high, plants are less likely to
collaborate with fungi, meaning that they become worse at absorbing nutrients.
"Through a range of experiments,
we have demonstrated that a plant does not produce the CLE53 gene if it lacks
phosphorus. However, when the phosphorus levels in a plant are high, or if the
plant is already symbiotically involved with a fungus, then the level of CLE53
increases. Our study demonstrates that CLE53 has a negative effect on a plant's
ability to enter into symbiosis with a fungus, and thereby absorb phosphorus
most effectively," says Thomas Christian de Bang.
Requires CRISPR approval
The genomic editing of plants is
legal in a number of non-EU countries -- e.g., China, the US, Switzerland and
the UK. However, within the EU, there is no general acceptance of gene-editing
methods, such as CRISPR, to alter plants and foodstuffs.
Therefore, the researchers'
discovery has, for the time being, a poorer chance of being used in Denmark and
the rest of the EU.
"One can use the technology in
other parts of the world, and getting started would be relatively
straightforward. My guess is that within five years, plants will be tested and
refined in such a way that they become more symbiotically involved with fungi
and absorb more phosphorus. Here in Denmark and throughout the EU, an acceptance
is required for gene editing and an amended approach to approval procedures for
these types of plants," says Thomas Christian de Bang.
Facts:
90% of all plants engage in
symbiotic relationships with mycorrhizal fungi, which popularly said, extend the
root networks of plants, thus helping them to obtain enough phosphorus, water
and other nutrients.
In order to benefit from the
ability of mycorrhizal fungi to extract phosphorus from soil, a plant must feed
it with fat and sugar. To avoid spending too much energy on the sponge, if for
example, it is experiencing high phosphorus levels or has already been colonised
by a fungus, the plant may switch off symbiosis.
It is estimated that Danish farms
fertilise with roughly 30 kilos of phosphorus per hectare of land. Of this,
roughly 30 percent makes its way to crops, while the remaining 70 percent binds
to soil.
With rain, some of this
accumulated phosphorus is flushed away via surface runoff, into nearby streams,
lakes and the sea. This increases algae growth and can kill both plants and
wildlife. Phosphorus is a finite natural resource, one that is expected to
eventually be depleted.
The research is funded by the
Novo Nordisk Foundation and the University of Copenhagen
Previous research has shown that
a similar mechanism exists for symbiosis between legumes and rhizobium bacteria.
This involved a CLE gene as well, albeit a different one than the researchers
have now discovered.
Story Source:
Materials provided by University
of Copenhagen. Note: Content may be edited for style and length. Journal
Reference: Thomas C de Bang, Patrick X Zhao, Xinbin Dai, Kirankumar S Mysore,
Jiangqi Wen, Gonzalo Sancho Blanco, Katrine Gram Landerslev, Clarissa Boschiero,
Magda Karlo. The CLE53-SUNN genetic pathway negatively regulates arbuscular
mycorrhiza root colonization in Medicago truncatula. Journal of Experimental
Botany, 2020; DOI: 10.1093/jxb/eraa193
Source: Science Daily