How An Amino Acid Can Control A Plants’ Breath

Plant scientists have demonstrated how a type of amino acid helps to regulate the opening and closing of tiny plant pores called stomata.

AsianScientist (Dec. 20, 2016) – Researchers at the Institute for Basic Science (IBS) have identified a novel calcium channel that regulates the opening and closing of plant stomata. Published in Cell Reports, this discovery helps to clarify how plants maintain and adjust an adequate intracellular calcium level for their growth and breathing.

Plants breathe and ‘sweat’ through stomata, microscopic pores found on leaves, stems and other plant organs. Through the stomata, plants take up carbon dioxide for photosynthesis and breathe out the products of this process, oxygen and water vapor.

Dr. June M. Kwak and his colleagues at the IBS Center for Plant Aging Research focused on the role of calcium in the opening and closing of stomata. They found that calcium concentration inside guard cells, which surround stomata pores, is influenced by proteins called glutamate receptor homologs (GLRs), in particular GLR3.1 and GLR3.5.

The researchers produced Arabidopsis thaliana plants lacking GLR3.1 and GLR3.5 proteins and found that when grown in a medium with a concentration of calcium 95 percent lower than the normal soil, these plants have yellow dying inflorescences, similar to plants with blossom-end rot disorder, a condition caused by low soil calcium.

“These tips of inflorescence have cells that are rapidly growing and dividing, so they need a lot of calcium. However, plant cells are quite selfish with calcium, and they do not share it with other cells if they do not have enough,” explained Kwak.

Using aequorin, a protein that senses calcium and emits light of different color depending on the concentration of calcium, IBS scientists found that mutant plants deficient in GLR3.1/GLR3.5 have 25 percent lower concentrations of intracellular calcium. Then, they used electrophysiological techniques to verify that GLR3.1/GLR3.5 channels are activated by the amino acid L-methionine.

Results from a series of further experiments clarified that L-methionine opens the GLR 3.1/3.5 calcium channels and allows calcium ions to enter the cell. The elevation in intracellular calcium, in turn, activates other membrane channels, like the reactive oxygen species-activated calcium channels, leading to stomatal closure.

“In the future, we would like to understand the source of L-methionine, which type of cells provide it for the guard cells and in response to what kind of stimuli,” Kwak said.



The article can be found at: Kong et al. (2016) L-Met Activates Arabidopsis GLR Ca2+ Channels Upstream of ROS Production and Regulates Stomatal Movement.

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Source: Institute for Basic Science.
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