Protein cuts water loss in plants

  Last updated March 15, 2018 at 10:50 am

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Discovery of the mechanism to control pores in plant leaves could be a boon for dry country farmers.


Photomicrograph of stomata of a leaf, through which moisture is lost through respiration. Credit: iStock


For plants, respiration comes at a cost. In order to draw carbon dioxide in and thus drive photosynthesis, pores in leaves have to open – allowing water contained inside them to evaporate.


The trade-off is a critical one, especially for farmed crops. If respiration leads to too much water loss, the plants can weaken, hastening death in low-moisture environments.


New research, however, may have found a way to reduce the severity of the problem, producing more robust, less thirsty crops.


The scientists  from the University of Illinois in Chicago, led by Stephen Long, have established that a particular protein, dubbed Photosystem II Subunit S (PsbS), is central in controlling the degree to which the plant pores, known as stomata, open in response to sunlight.


To make their discovery, the scientists genetically altered and then bred a range of tobacco plants with different levels of PsbS, from undetectable to 3.7 times the wild-type baseline.


The transgenic plants were then planted out as trial crops in irrigated plots.


Long and his colleagues report that in the varieties containing above-normal levels of the protein, the stomata did not open as widely as standard commercial tobacco plants.


This did not affect levels of carbon dioxide intake – and thus photosynthetic efficiency – but it did decrease total water loss by a hefty 25 per cent.


The result is potentially good news for non-tobacco farmers. The genes responsible for producing PsbS are highly conserved across all photosynthesising plants, meaning the same water-conserving effect can be induced in other commercial species.


Long and his colleagues say the development of bioengineering strategies to bring this about are “urgently needed, especially considering the long timelines for developing new crop varieties”.


The paper was published in the journal Nature Communications.


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Andrew Masterson