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To control the intake of carbon dioxide for photosynthesis on the one hand and water loss through transpiration on the other, grasses contain "respiratory pores" (known as stomata) that open and close.
In contrast to many other plants, grass stomata generate lateral "helper cells." These cells allow grass stomata to open and close more quickly, enhancing plant-atmosphere gas exchange and resulting in water savings. For the current study, Prof. Dr Michael Raissig, Dr Heike Lindner and co-author Roxane Spiegelhalder from the Institute of Plant Sciences (IPS) at the University of Bern investigated the development of helper cells in the grass Brachypodium distachyon. They discovered two proteins that accumulate on opposite sides of a cell, acting like a "compass" to ensure the proper development of helper cells in grasses. The research results were published in the journal eLife. A cell compass for the development of helper cells Helper cells are formed by unequal, asymmetric cell division. In this process, a cell divides into a small cell, the helper cell, and a larger neighbouring cell. For this division to occur in the correct ratio and orientation, the cell needs landmarks. These landmarks act as points of orientation and are given by so-called polarity proteins, which accumulate on opposite sides of the cell and can thus define, for example, left and right or top and bottom. In this study, the Bern researchers discovered two polarity proteins that accumulate on two opposite sides. "In a sense, the two proteins act as a cellular compass and control the orientation of cell division and the development of helper cells. We found that helper cells do not form properly when one of these proteins is missing. This negatively influences the efficient and water-saving gas exchange of the grass," explains project leader Michael Raissig. Plant respiratory pores and climate change "I am always fascinated that the lack of a cell compass in a single cell type can affect the gas exchange dynamics and efficiency of the entire plant," says Michael Raissig. He says this is particularly relevant in light of climate change, which causes longer drought periods and excessive heat. Grasses play a central role in human food security; cereals such as corn, rice and wheat are all grasses and together provide more than half of the calories consumed by humans. "Therefore, it is of utmost importance to understand how plants "breathe" and how and why grasses form more efficient "breathing" pores," adds Raissig. While this study focuses mainly on developmental biology, these findings could be relevant to improving agricultural crops. "Stomata are the cellular gatekeepers between the leaf and the environment and are the first to respond to changes in climate," says PhD student and co-author Roxane Spiegelhalder. Therefore, she says, it is imperative to understand how and why grasses form the most efficient "gatekeepers" to "breathe" more water efficiently. How and whether these findings can be transferred to other crops, however, requires further research, Spiegelhalder concludes. (ANI)
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