TAU researchers find mechanism that regulates plant growth

"Determining the mechanisms that underlie the developmental plasticity of plants is essential for agricultural innovation," Prof. Shaul Yalovsky explained.

By AARON REICH
An employee inspects the leaf of a cannabis plant at a medical marijuana plantation in northern Israel. (photo credit: NIR ELIAS / REUTERS)
An employee inspects the leaf of a cannabis plant at a medical marijuana plantation in northern Israel.
(photo credit: NIR ELIAS / REUTERS)
A new Tel Aviv University study finds that a unique mechanism involving calcium, the plant hormone auxin and a calcium-binding protein is responsible for regulating plant growth.
Researchers say that a protein that binds to calcium regulates both auxin responses and calcium levels, creating an interface that determines how plants grow.
The study, published on July 11 in PLOS Biology, was led by Prof. Shaul Yalovsky of TAU's George S. Wise Faculty of Life Sciences, with research conducted by graduate students Ora Hazak and Elad Mamon and colleagues. It is the fruit of a collaboration with Prof. Joel Hirsch of TAU's Department of Biochemistry and Molecular Biology, Prof. Jörg Kudla of the University of Münster and Prof. Mark Estelle of the University of California, San Diego.
Environmental conditions have a large role in shaping plant growth, especially factors such as light, humidity, drought and salinity, among others. However, the means by which environmental signals are integrated by plants and the developmental processes encoded in their genes remained a mystery.
"Determining the mechanisms that underlie the developmental plasticity of plants is essential for agricultural innovation," Yalovsky explained. "It was believed for several decades that calcium and auxin interfaced during a plant's development, but the exact mechanisms underlying this 'cross-talk' were unclear.
"We have discovered that auxin communicates with calcium through a binding protein called CMI1. We believe our research will have long-term applications for farmers and agricultural experts, who will be able to harness this information to adapt future generations of plants to extreme environmental conditions such as high temperatures, drought and high salinity in the soil."
The levels of the hormone auxin are what determines where on a plant leaves develop, as well as how roots develop and determining a plant's number of branches.The plant's response to signals such as high or low temperatures, touch and soil salinity are influenced by calcium and auxin levels.
"Prior to our research, it was unclear how the interaction between calcium and auxin took place," Yalovsky added. "Now we know that when auxin levels are high, the levels of the newly discovered binding protein CMI1 are high. We discovered that this protein regulates auxin responses and calcium levels and that it binds to calcium."
Responses to auxin are either very rapid or slow. The slower responses take place over the span of hours and days and are dependent on certain gene pathways, while the rapid responses last only minutes and are enabled by CMI1., which depends on calcium.
"We used a very wide collection of tools and approaches that allowed us to carry out our analyses starting from the level of the whole plant, down through the level of tissue and cells, and finally to the level of molecules," Yalovsky concluded. "The next step will be to identify the cellular components that interact with the protein that we discovered."