Wave of gene expression gives root tips wild ride

Sep 10, 2010 By Kendall Morgan
The cells of growing root tips glow as gene expression peaks, leaving behind a series of spots where branching lateral roots will later emerge. Phil Benfy lab, Institute for Genome Sciences & Policy

Duke researchers have found a surprising parallel between the development of an animal's spinal column and a plant's root system. Both appear to be controlled by a "molecular clock" that governs a regular spatial pattern of development.

"It appears there are similar underlying processes in both and animals, suggesting that the number of ways the problem can be solved is limited," said Philip Benfey, director of the Center for at the Duke Institute of & Policy. "This must be a very efficient solution."

The clock is driven by a wave of gene expression that travels up from the tip of the roots and reaches its peak every six hours, Benfey's team reports in the September 10th issue of Science. The wave is made up of thousands of genes, including two separate groups that trade off their activity; when one group is high, the other is low and vice versa.

This video is not supported by your browser at this time.
Research video showing glowing spots of gene expression in Arabadopsis thaliana root tips.

In vertebrates, the early formation of transient structures called somites that are the precursors of vertebrae is similarly periodic, depending on a rhythmic wave of gene expression that moves though the developing tissue. When the wave of gene expression encounters a set of responsive cells, those cells are specified to become the next somite. This mechanism ensures each vertebrate species ends up with the correct size and number of vertebrae.

In the case of plant roots, these peaks of gene expression mark the spots where root branches can later form. It doesn't mean those sites will necessarily sprout new root branches, but it does mean they are "competent" to do so. "This wave is the first step in a multistep process," Benfey said. "It gets the spacing right."

The researchers were able to uncover this pattern by measuring gene expression separately in the upper and lower portions of 20 individual roots of Arabidopsis thaliana, each at different points along the cycle. They then used a sophisticated algorithm to piece together a complete time series of one cycle or oscillation.

The timing of the gene expression wave is largely independent of the rate at which a root is growing. As a result, roots that grow more slowly will have the potential to pack in more branches over a short length. Those growing quickly, as they presumably would when the living is easy and there is little need to "branch out," would end up with more widely spaced branch roots.

"Producing pre-determined sites in a periodic fashion seems to be an efficient solution to coordinate growth with the exploration of soil for resources," said Miguel Moreno-Risueno, a post-doctoral researcher in Benfey's lab who led the study.

The team still needs to work out exactly what is happening at the cellular level. For instance, they say that the wave moves from one cell to the next, but that isn't completely clear.

Collaborators on the study include Jaimie Van Norman and Jingyuan Zhang, of Duke; Antonio Moreno of Instituto de Acustica in Spain; and Sebastian Ahnert of the University of Cambridge. The work was supported in part by grants from DARPA and the National Institutes of Health.

Explore further: Synthetic biology on ordinary paper, results off the page

Related Stories

New evidence in plants shows micro-RNA can move

Apr 21, 2010

Ever since tiny bits of genetic material known as microRNA were first characterized in the early 1990s, scientists have been discovering just how important they are to regulating the activity of genes within cells.

Scientists find direct line from development to growth

Jun 30, 2010

It may seem intuitive that growth and development somehow go together so that plants and animals end up with the right number of cells in all the right places. But it is only now that scientists at the Duke ...

Root or shoot? EAR calls the shots

Feb 07, 2008

Controlled by a tightly regulated choreography that determines what should go up and what should go down, plants develop along a polar axis with a root on one end and a shoot on the other.

Hyped-up hopes for hairy roots as biofactories

Oct 08, 2007

Scientists are reporting an advance towards tapping the immense potential of 'hairy roots' as natural factories to produce medicines, food flavorings and other commercial products. Their study is scheduled for the November/December ...

Researchers root out new and efficient crop plants

Jul 30, 2008

A part of the global food crisis is the inefficiency of current irrigation methods. More irrigated water evaporates than reaches the roots of crops, amounting to an enormous waste of water and energy.

Recommended for you

Team advances genome editing technique

Oct 21, 2014

Customized genome editing – the ability to edit desired DNA sequences to add, delete, activate or suppress specific genes – has major potential for application in medicine, biotechnology, food and agriculture.

User comments : 0