Study Finds Hormonal Interactions Regulate Growth of Plant Roots

A team of scientists from the John Innes Centre (JIC) in the United Kingdom and Sapienza University in Rome, Italy, combined mathematical and computer modelling with molecular genetics to show how roots regulate their growth through the interactions of two antagonistic hormones, auxin and cytokinin.

As roots grow and meristem cells at the tip continuously divide, they are left behind in relation to the moving root tip. When these cells reach a certain distance from the tip, called the transition position, they stop dividing and instead, start elongating until reaching their maximum lengths. According to Dr. Veronica Grieneisen, cells "know" that they have reached the transition position because of positional information.

The teams of Dr. Grieneisen and Dr. Stan Marée at JIC have shown that the hormone auxin was present at very high levels at the root tip to maintain certain cells as stem cells, as a result of fast dynamics of auxin swirling around. These currents of auxin allowed the auxin maximum and its associated gradient to move together with the growing root. Further work showed that auxin does not regulate the transition alone, but antagonistic cross-talk between auxin and another hormone, cytokinin, stabilize the size of the meristem zone, and even change it, either stabilizing root growth, or changing its velocity. They found that cytokinin's influence generated a very typical pattern of auxin concentrations in the root.

For more details, read the JIC News and Events.