Root symbiosis is regulated through nutrient status of plants
Phosphate nutrition of plants through symbiosis with fungi

Date:
February 8, 2022
Source:
Technical University of Munich (TUM)
Summary:
Phosphorus is one of the most important nutrients for plants. Among
other functions, it is needed to create substances for the
plant's immune system, for the healthy development of seeds and
for root growth.

Researchers have now demonstrated how a root symbiosis with fungi
is driven at the molecular level by the plant's phosphate status.



FULL STORY ==========================================================================
Land plants absorb phosphate better when they collaborate with certain
soil fungi. Arbuscular mycorrhiza (AM), a symbiosis with such fungi,
is used by more than 80 percent of plants. The fungi penetrate the
root cortex cells and form hyphal networks in the soil. These take up
phosphate from the soil and transport it directly into the root, where
it is released into the root cells via tree-shaped fungal structures
called arbuscules.


========================================================================== Plants regulate the establishment of symbiosis "Interestingly, the
plant can regulate the establishment of the symbiosis according to its physiological condition. The symbiosis is promoted at low plant phosphate status and is inhibited when the plant has sufficient phosphate, for
example as a result of fertilizer use," says Caroline Gutjahr, Professor
for Plant Genetics at TUM. "This likely happens in order to conserve
organic carbon, which the plant supplies to the fungus." Although
this phenomenon was first observed around 50 years ago, the molecular
mechanism for inhibiting the arbuscular mycorrhiza at high phosphate
status was unknown.

A protein called PHR is a key transcription factor in the process.

Transcription factors are proteins that control the copying of DNA into
mRNA, thus ensuring that finally the required quantity of a protein
is formed. PHR activates genes that enable the plant to respond to a
phosphate deficiency.

Experiments with rice -- one of the most important agricultural crops
"We wanted to find out how the formation of arbuscular mycorrhiza
is regulated depending on phosphate availability. Our hypothesis was
that PHR might be responsible," says Prof. Gutjahr. In addition to lab
results with rice and the model legume Lotus japonicus, the researchers
also conducted an experiment in soil from rice fields. They were able
to show that PHR is needed to promote AM symbiosis when soil phosphate
is low to ensure normal grain yields.

A key result of the study is that PHR not only regulates classical
phosphate deficiency genes, but also an entire group of genes required
for the establishment and function of AM. These include, for example, biosynthesis genes for the hormone strigolactone. This hormone is produced
by the plant and released into the soil where it activates and attracts
the fungus.

Potential for sustainable agriculture AM symbiosis has enormous
potential for application in sustainable agriculture by reducing the
need for artificial fertilizers. "Our insights could be used to modify
the phosphate sensitivity of plants through selective breeding or gene editing," says Prof. Gutjahr.

The improved uptake of phosphate is not the only benefit of AM. It also promotes the absorption of other nutrients such as nitrogen, potassium
and sulphate and improves plant resistance to various stressors such
as drought.

"By tuning PHR, for example, we could reduce the phosphate sensitivity
of plants and promote the symbiosis at higher concentrations of phosphate
in the soil and thus use its other benefits for agricultural production,"
says the Professor of Plant Genetics.

========================================================================== Story Source: Materials provided by
Technical_University_of_Munich_(TUM). Note: Content may be edited for
style and length.


========================================================================== Journal Reference:
1. Debatosh Das, Michael Paries, Karen Hobecker, Michael Gigl, Corinna
Dawid, Hon-Ming Lam, Jianhua Zhang, Moxian Chen, Caroline Gutjahr.

PHOSPHATE STARVATION RESPONSE transcription factors enable
arbuscular mycorrhiza symbiosis. Nature Communications, 2022; 13
(1) DOI: 10.1038/ s41467-022-27976-8 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/02/220208105238.htm
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