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Calcium regulation of transcription in plants

Published on February 20, 2012 Reviewed on August 12, 2020   24 min

A selection of talks on Gynaecology & Obstetrics

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0:00
I'm Professor Hillel Fromm, Head of the department of molecular biology and ecology of plants at Tel Aviv University. Today I will talk about calcium regulation of transcription in plants.
0:12
First, I will give an overview of the origin and status of calcium in plant cells. And I will specifically address the relationship between the calcium in the cytosol and in the nucleus. I will then describe mechanisms by which calcium regulates gene expression. And I will further on give examples of how calcium regulated transcription is involved in plant defenses, in biotic and abiotic stresses. And how calcium regulation of transcription is involved in hormonal function and plant growth.
0:40
One of the intriguing properties of calcium in plant cells is that calcium is involved with any interaction of plants with the environment. This includes the biotic and abiotic environments. It includes responses to physical stimuli like light, heat, cold, mechanical stress and to chemical stimuli like salinity, drought and hypoxia.
0:59
The important role of calcium in cellular life and in plants cells specifically, that we probably traced back to early evolution of cell. Due to the properties of calcium, it's fast binding to proteins and other molecules. It's strong binding, high availability, and limited solubility. Early cellular life required ejection of calcium from the cells to create a situation where the concentrations of calcium in the cell is very low. And thus creating a gradient of four orders of magnitude of calcium from outside to inside. This was probably the initial step to the evolution of calcium as a signaling system in plants.
1:38
When we look at the typical plant cells, we see that the concentration of calcium in the cytosol it is between 100 to 200 nanomolar. The outside concentration of calcium in Apoplast is between one to ten millimolar. Calcium has the machinery to pump out calcium from within the cell or release calcium on the outside of from an intracellular storage compartments. And this compartment include chloroplasts, mitochondria, the And most importantly in plants the vacuole which contains concentrations of calcium to the ten millimolar range. Upon perception of signals from the environment, calcium will be released into the cytosol either from the outside or from intracellular compartments, and will create a calcium signature. So for each stimulus from the outside will be a different pattern of calcium that is called a calcium signature. The question now is how genes are regulated by calcium. Since the genes are in the nucleus, we have to ask the questions of what happens with calcium in the nucleus. The nucleus is not a sealed envelope but actually contains pores that can even let proteins go into the nucleus. So for many years it was assumed that calcium simply moves freely through these pores into the nucleus. However, now it's believed that calcium cannot move freely through these pores. It may go through these pores under certain circumstances. However the most interesting thing is that the nucleus has calcium storage and release machinery in the nuclear envelope.

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