Tissue specific aquaporin expression for seedling water stress resistance

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This plant science project combines cell biology and plant physiology to understand how seeds take up water during germination and post-germination seedling growth and how we can control this process to develop crops that can germinate and establish in water stress conditions. Rapid plant tissue expansion after seed germination is crucial for crop establishment and plant uniformity and it directly impacts on quality and yield at the end of the crop cycle. For these reasons early vigour is an important target for crop improvement. Most cells (including seed cells) take up water through protein water channels called aquaporins (AQP). While a lot is known about AQP structure and function in plant roots and leaves, very little is known about their role in seed germination and post-germination seedling growth. Our project directly addresses this question. AQP exist on different cellular membranes and water intake is usually controlled by AQP on the outer cell membrane (the plasma membrane). Remarkably, we have found that in seeds the AQP that are normally present on the plasma membrane are NOT produced until AFTER the seed has germinated. So what is controlling water entry during germination? We have discovered that AQP that normally reside on the membrane of the vacuole (the tonoplast) are also found at the plasma membrane during seed maturation and germination. Therefore it seems that seeds have a unique way of regulating water intake by sending tonoplast AQP to the plasma membrane.We have also discovered that plants modified to produce very high amounts of seed AQP are able to germinate and grow in conditions of water stress, performing significantly better than wild-type plants. Therefore we hypothesise that seed AQP are major controllers of water flow in seeds and early seedling growth that can be used to generate plants that cope better with drought conditions.Our project aims at understanding the role of AQP by studying the way the tonoplast AQP are targeted to the plasma membrane. We also propose to manipulate both the amount and type of AQP present on the seed cells' plasma membrane and correlate it with the ability of seeds to germinate and the vigour of post-germination seedling growth using a range of water stress conditions. We will perform the basic experiments in the model plant Arabidopsis but, in parallel we will also perform pilot experiments in Brassica oleracea, a crop for which co-ordinated germination and early vigour can have a direct, major impact on final yield. By the end of the project we aim to have improved understanding of the regulation of AQP during germination and early sedling growth and to have established strategies to manipulate AQP in order to maximise early vigour and water stress resistance.