Utrecht University: Decade-long study leads to molecular atlas of crop roots

New genetic data could help food crops like tomatoes and rice survive longer, more intense periods of drought on our warming planet. The data provides a molecular atlas of crop roots, published by an international team of plant biologists.

Over the course of the last decade, an international research team sought to create a molecular atlas of crop roots. The team focused on plants roots, as this is where plants first detect the effects of drought and other environmental threats. The researchers uncovered genes that scientists can use to protect the plants from these stresses.

Their work, published in the journal Cell external link achieved a high degree of understanding of the root functions. “With this molecular plant atlas, we gain huge insights in what defines a certain cell, and what its genetic underpinnings are’, says Kaisa Kajala, plant biologist at Utrecht University.

With this molecular plant atlas, we gain huge insights in what defines a certain cell, and what its genetic underpinnings are

The data yielded information about genes that tell the plant to make three key things. One of them is plant tissue called xylem. This tissue consists of hollow, pipe-like vessels that transport water and nutrients from the roots all the way up to the shoots. Because of this function, xylem are very important to shore up plants against drought, as well as salt and other stresses. Without transport in xylem, the plant cannot create its own food via photosynthesis.

Cork substance
In addition to some typical players needed to form the xylem, new and surprising genes were found. The second key set of genes identified by the researchers are those that direct an outer layer of the root to produce lignin and suberin. Suberin is the key substance in cork and it surrounds plant cells in a thick layer, holding in water during drought.

Now that the genes regulating the moisture barrier have been identified, key elements can be enhanced
Crops like tomatoes and rice have suberin in their roots. Apple fruits have suberin surrounding their outer cells. Anywhere it occurs, it prevents the plant from losing water. Lignin also waterproofs cells and provides mechanical support.

Now that the genes regulating this moisture barrier have been identified, these compounds can be enhanced, according to the researchers.

A common thread
Though this study analyzed only three plants species, the team believes the findings can be applied more broadly. This is because genes that encode for a plant’s root meristem turned out to be remarkably similar between tomato, rice, and Arabidopsis thaliana, a weed-like plant used by biologists as a model plant. The meristem is the growing tip of each root, and it’s the source of all the cells that make up the root.

“Having knowledge of it can help us develop better root systems,” says Julia Bailey-Serres, plant biologist at the University of California and also involved in this study. “It’s the region that’s going to make the rest of the root, and serves as its stem cell niche. It dictates the properties of the roots themselves, such as how big they get.”

Being able to modify the meristem of a plant’s roots will help engineer crops with more desirable properties
The hidden half of a plant

The researchers note that, when farmers are interested in a particular crop, they select plants that have features they can see, such as bigger, more attractive fruits. Selecting properties below the ground, which they can’t see, is much more difficult.

“The ‘hidden half’ of a plant, below the ground, is critical for breeders to consider if they want to grow a plant successfully,” says Siobhan Brady, biologist at the University of California and lead author of the Cell publication. “Being able to modify the meristem of a plant’s roots will help us engineer crops with more desirable properties.”

Future research
“Doing this research using crop plants took a lot of time and labour”, says Kajala. “But it opens so many doors, both for applications and future research.”

This research took a lot of time and labour. But it opens so many doors, both for applications and future research

Dr. Kaisa Kajala
Dr. Kaisa Kajala
Plant Ecophysiology
“My next research direction is expanding to even more plant species in order to look at the evolution of suberin and lignin pathways, especially for the protective outer layer of the root.” For this research, Kajala acquired a Vidi grant from the Dutch Research Council.