Blushing plants reveal when fungi are growing in their roots

Date:
July 23, 2021
Source:
University of Cambridge
Summary:
Scientists have created plants whose cells and tissues 'blush'
with beetroot pigments when they are colonized by fungi that help
them take up nutrients from the soil. This is the first time this
vital, 400 million year old process has been visualized in real
time in full root systems of living plants. Understanding the
dynamics of plant colonisation by fungi could help to make food
production more sustainable in the future.



FULL STORY ========================================================================== Almost all crop plants form associations with a particular type of fungi
- - called arbuscular mycorrhiza fungi -- in the soil, which greatly
expand their root surface area. This mutually beneficial interaction
boosts the plant's ability to take up nutrients that are vital for growth.


==========================================================================
The more nutrients plants obtain naturally, the less artificial
fertilisers are needed. Understanding this natural process, as the
first step towards potentially enhancing it, is an ongoing research
challenge. Progress is likely to pay huge dividends for agricultural productivity.

In a study published in the journal PLOS Biology, researchers used the
bright red pigments of beetroot -- called betalains -- to visually track
soil fungi as they colonised plant roots in a living plant.

"We can now follow how the relationship between the fungi and plant
root develops, in real-time, from the moment they come into contact. We previously had no idea about what happened because there was no way to visualise it in a living plant without the use of elaborate microscopy,"
said Dr Sebastian Schornack, a researcher at the University of Cambridge's Sainsbury Laboratory and joint senior author of the paper.

To achieve their results, the researchers engineered two model plant
species - - a legume and a tobacco plant -- so that they would produce
the highly visible betalain pigments when arbuscular mycorrhiza fungi
were present in their roots.

This involved combining the control regions of two genes activated
by mycorrhizal fungi with genes that synthesise red-coloured betalain
pigments.

The plants were then grown in a transparent structure so that the root
system was visible, and images of the roots could be taken with a flatbed scanner without disturbing the plants.

Using their technique, the researchers could select red pigmented parts
of the root system to observe the fungus more closely as it entered
individual plant cells and formed elaborate tree-like structures --
called arbuscules -- which grow inside the plant's roots. Arbuscules take
up nutrients from the soil that would otherwise be beyond the reach of
the plant.

Other methods exist to visualise this process, but these involve
digging up and killing the plant and the use of chemicals or expensive microscopy. This work makes it possible for the first time to watch by
eye and with simple imaging how symbiotic fungi start colonising living
plant roots, and inhabit parts of the plant root system over time.

"This is an exciting new tool to visualise this, and other, important
plant processes. Beetroot pigments are a distinctive colour, so they're
very easy to see. They also have the advantage of being natural plant
pigments, so they are well tolerated by plants," said Dr Sam Brockington,
a researcher in the University of Cambridge's Department of Plant
Sciences, and joint senior author of the paper.

Mycorrhiza fungi are attracting growing interest in agriculture. This
new technique provides the ability to 'track and trace' the presence
of symbiotic fungi in soils from different sources and locations. The researchers say this will enable the selection of fungi that colonise
plants fastest and provide the biggest benefits in agricultural scenarios.

Understanding and exploiting the dynamics of plant root system
colonisation by fungi has potential to enhance future crop production in
an environmentally sustainable way. If plants can take up more nutrients naturally, this will reduce the need for artificial fertilisers --
saving money and reducing associated water pollution.

========================================================================== Story Source: Materials provided by University_of_Cambridge. The original
story is licensed under a Creative_Commons_License. Note: Content may
be edited for style and length.


========================================================================== Journal Reference:
1. Alfonso Timoneda, Temur Yunusov, Clement Quan, Aleksandr Gavrin,
Samuel
F. Brockington, Sebastian Schornack. MycoRed: Betalain pigments
enable in vivo real-time visualisation of arbuscular mycorrhizal
colonisation. PLOS Biology, 2021; 19 (7): e3001326 DOI:
10.1371/journal.pbio.3001326 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/07/210723105242.htm

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