Greater understanding of plant hormone results in stem cells that grow shoots

Researchers at Dartmouth College have identified how a well-known plant hormone targets genes to regulate plant growth and development. The finding could allow scientists to establish organ-growing stem cells for grains like rice and corn, and may ultimately lead to solutions to stubborn agricultural problems.

The study, appearing in the Proceedings of the National Academy of Sciences, describes how cytokinin activates the transcription factor ARR10 to control gene expression in the Arabidopsis plant - a member of the mustard family commonly used as a model in plant biology.

Cytokinin is a hormone that regulates numerous processes in plants, including cell division, growth of shoots and roots, grain yield and greening.

"The question has always been how cytokinin regulates so many different processes within a plant," said Eric Schaller, a professor of biological sciences at Dartmouth College. "Now we know the genes that are the primary targets of cytokinin, and we can provide the toolbox for manipulating the plant hormone response."

According to the paper, results from the analysis "shed light on the physiological role of the type-B ARRs in regulating the cytokinin response, the mechanism of type-B ARR activation, and the basis by which cytokinin regulates diverse aspects of growth and development as well as responses to biotic and abiotic factors."

As part of the study, conducted in collaboration with the University of North Carolina Charlotte and the University of North Carolina at Chapel Hill, researchers were able to use the new understanding of how cytokinin works to grow shoots in tissue culture under conditions in which these plant organs normally do not form.

To make the plant tissues grow shoots in vitro, the research team increased the cytokinin sensitivity in the Arabidopsis plant. This resulted in activation of the WUSCHEL target gene, which is a key regulator of shoot development. The result confirms understanding of how to establish stem cells that lead to different types of organ growth.

"What we have done is activate the plant to make a stem cell center for a shoot to form," said Schaller. "By finding the direct targets of what is impacted by cytokinin, we can fine-tune our focus in the future."

According to Schaller, this research sets the stage for further work that could help improve yield of important agricultural products like rice and corn.