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New developments in plant resistance to drought

Plant stomata open or close in response to their needs, in addition to water stress or pathogen attack. A team from the Biam and its partners have demonstrated the role of the protein AQP in stomatal closure movements.

Published on 29 January 2018

Today, there is concern about how to improve farming practices in areas subject to drought. It is essential to understand the mechanisms underlying drought resistance and effective plant water use so as to adapt to changes in global climate. In plants, the majority of water loss occurs via pores on the leaf surface, called stomata. The degree of stomatic pore opening varies and controls the rate of water vapor diffusion by the plant. In addition to controlling water loss, the stomata also allow the required influx of CO2 into the leaf for photosynthesis. Thus, the main challenge of the stomata is to optimize CO2 capture while limiting excessive water loss.

Stomata are also a potential gateway for pathogens. Abscisic acid (ABA), the key hormone in the plant response to water deficiency, triggers, via the production of hydrogen peroxide (H2O2), signaling processes that lead to stomatic closure.

Aquaporins (AQP) are proteins that form channels that promote the passage of water molecules through cell membranes in higher plants. Until now, their role has been very hypothetical. To learn more about them, researchers from the CNRS and the INRA in Montpellier, in collaboration with the Biam and the Nara Institute of Science and Technology (Japan), showed that plants lacking the gene encoding the AQP protein PIP2;1 present a stomatic closure defect in response to water stress and release of the ABA hormone. Nevertheless, these plants show normal responses to darkness, light and CO2. The use of a H2O2-sensitive fluorescent probe (HyPer) revealed the accumulation of H2O2 in wild plants in response to the ABA hormone. This accumulation is abolished in mutant plants.

"This work provides the first direct genetic and physiological evidence of a role for aquaporins in stomatic movements", explains Nathalie Leonhardt, a researcher at the Biam. "It allows us to propose that PIP2;1 simultaneously plays hydraulic and signaling roles, by facilitating the transport of water and H2O2 across the cell membrane". This study also provides essential knowledge for engineering more drought-tolerant plants.

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