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Philip White



 Zoology Dept., College of Science, Building (5)

Office: 2B122

Telephone: 4675753

Project Title

The Evolution of Sodium Accumulation in the Caryophyllales

Project Summary

Excessive sodium (Na) concentrations in the soil solution constrain agricultural production on saline soils, such as those occurring in Saudi Arabia. Nevertheless, halophytic crops, such as quinoa (Chenopodium quinoa) and other members of the Caryophyllales, can be cultivated on saline land. The molecular basis underpinning the ability of these adapted crops to tolerate saline soils is largely unknown. This project will provide information on the physiology and molecular biology associated with the ability of Caryophllales in general, and quinoa in particular, to tolerate saline soils. This might be used to improve their tolerance of salinity and crop production.

Sodium is essential for both C4 and CAM photosynthesis. It also serves as a vacuolar osmoticum that helps maintain cell turgidity in saline environments. We have recently observed that many Caryophyllales species constitutively accumulate exceptionally large Na concentrations in their leaves, when compared to most other angiosperms, even when they are grown in solutions containing low (non-saline) Na concentrations (PJ White, unpublished data). The Caryophyllales comprises about 11,000 plant species partitioned into 35 plant families and three unassigned genera. A high proportion of these species exhibit C4 or CAM photosynthesis, especially those in the Amaranthaceae family, and many are true halophytes. We have also observed that, although most Caryphyllales appear to be capable of taking up large amounts of Na from solutions with low Na concentrations, this ability is magnified in species from the Aizoaceae family and in many species in the Amaranthaceae family. The latter family includes both crop plants, such as quinoa, beet (Beta vulgaris) and spinach (Spinacia oleracea), and the model genus Atriplex for which many molecular biological resources are available. The applicant’s laboratory has studied plant mineral nutrition for over 25 years. In particular, they have expertise in quantifying phylogenetic effects on plant mineral composition (the ionome) and investigating the evolution of plant ionomes1-7. They also have experience in comparative transcript profiling, for example in identifying genes involved in zinc-hyperaccumulation through multiple pairwise comparisons of genetically related zinc-hyperaccumulator and non-accumulator plant species3,6,7. This expertise will be used in the current project to explore the evolutionary origins of Na (hyper)accumulation in the Caryophyllales and to investigate the physiological and molecular mechanisms underpinning this trait.