Formation, physical structure and biological function of plant wax compounds

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Droughts cause severe losses in many agronomy sectors in Canada and abroad every year. Therefore, to feed a growing population facing global climate change, crop lines with improved drought tolerance are urgently needed. Current crop varieties suffer from dry, hot conditions mainly because they loose water through excessive transpiration across their vast aerial surfaces. In contrast, many wild plant species have skins sealed to minimize transpiration, allowing them to grow in savannas or even deserts. To prevent water loss, the skins of plants (and humans) are coated with wax mixtures comprising similar compounds in all species. However, despite these similarities, the wax coatings of many wild plants have sealing properties far superior to our current crops, suggesting that relatively small changes in the wax composition of our crops may greatly improve their drought tolerance. Much research has gone into manipulating plant wax compositions, but with limited effects on wax performance so far. Firstly, even plant lines with drastically increased overall wax amounts had only modestly enhanced transpiration control, suggesting that performance depends more on wax composition than quantity. However, also those studies attempting to enhance the barrier by changing composition had limited success, likely because relatively little chemical information and experimental tools were available. All previous efforts were restricted to wax compounds common to all species, with similar molecular structures. Instead, key compounds determining wax structure must be identified in select species, and their effect on transpiration control quantified depending on concentrations and conditions (temperature). In this project, we propose to investigate the effect of special wax compounds that, due to their outstanding structures, likely have strong effects on the sealing properties of the wax. The planned experiments build on recent progress in my lab, where we have developed all the necessary tools to investigate the chemical composition, physical structure, and biological function of complex wax mixtures lining the leaves of diverse species. In particular, we have identified many wax compounds (ketones) with kinks in their long carbon chains that disturb the molecular packing of the wax mixture. We will now study the formation of these ketones, their effects on the physical structure of the wax mixtures, and their impact on drought tolerance. To this end, the native waxes of Arabidopsis, wheat and other species containing wax ketones will be compared, and select wax compounds will be combined in artificial mixtures to test their effects. This research work will be performed by graduate and undergraduate students, who will gain important experience in their projects using state-of-the-art instruments along with soft skills needed for future employment in industry, government or academia.