The cells and tissues ’blush’ with beetroot pigments when colonised by fungi that help them take up nutrients from the soil
Scientists of the University of Cambridge have recently created plants whose cells and tissues ’blush’ with beetroot pigments when they are colonised 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 visualised 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.
Almost all crop plants form associations with a particular type of fungi – called arbuscular mycorrhiza fungi – in the soil, which greatly expands their root surface area. This mutually beneficial interaction boosts the plant’s ability to take up nutrients that are vital for growth.
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.
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.
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.
