Gene determines how far down roots go

Biologists have discovered a gene they believe determines how deep roots go in the soil, and this, they hope, will help scientists understand how plants address seasonal variance in rainfall and can adapt to changing climates.

The work was led by a team from the Salk Institute in California, US.

They used the model plant thale cress (Arabidopsis thaliana) to identify genes and their variants that regulate the way auxin – a hormone that is a key factor in controlling the root system architecture – works. 

Though auxin was known to influence almost all aspects of plant growth, it was not known which factors determined how it specifically affects root system architecture.

“The roots of A. thaliana are incredibly small so they are not easily visible, but by slicing the plant in half we could better observe and measure the root distributions in the soil,” says first author Takehiko Ogura.

They found that a gene called EXOCYST70A3 directly regulates root system architecture by controlling the auxin pathway without disrupting other pathways. It does this by affecting the distribution of PIN4, a protein known to influence auxin transport. 

When the EXOCYST70A3 gene, was altered, the orientation of the root system shifted, and more roots grew deeper into the soil.

“Biological systems are incredibly complex, so it can be difficult to connect plants’ molecular mechanisms to an environmental response,” says Ogura. 

“By linking how this gene influences root behaviour, we have revealed an important step in how plants adapt to changing environments through the auxin pathway.”

The findings will be published in a paper in the journal Cell. It is currently available on the pre-print biology server bioRxiv.