Exploiting Brachypodium distachyon to elucidate drought tolerance mechanisms : Linking gene expression with changes in cell wall chemistry

Background: Drought is an important environmental stress limiting the productivity of major crops throughout the world. Recent reports suggest that periods of drought will be increasingly common. A high priority for the future is to develop drought-tolerant crops that produce significant yields with reduced amounts of water. The plant cell wall plays an important role in conferring drought tolerance as this involves restructuring of the cell wall to allow growth at lower water content. Water loss affects turgor pressure, affecting the extensibility of the plant cell wall (1). Drought leads to changes in the expression of cell wall related genes (2), the activity of cell wall matrix enzymes (3), cell wall polysaccharides (3) and the accumulation of cell wall phenolics such as lignin and ferulic acid (4,5). Given the apparent importance of cell wall related processes to drought resistance, there is a pressing need for correlating changes in expression of genes involved in cell wall biogenesis with changes in secondary metabolite profiles and cell wall polysaccharides during drought / water-deficit stress. DLF-Trifolium has one of the largest grass research and breeding programmes and is continually seeking to exploit new opportunities to improve the quality and reliability of its varieties. This project will apply IBERS-based expertise in cell wall biology, abiotic stress and specifically in the new model grass Brachypodium distachyon to the DLF-Trifolium grass breeding programmes. It will rapidly identify genetic elements (markers and genes) which will be translated to DLF-Trifolium breeding programmes, providing immediate economic impact. Aim & Strategy: This project will establish the links between changes in cell wall chemistry and regulatory gene expression with drought tolerance by exploiting variation in the model grass Brachypodium distachyon which is rapidly developing as the Arabidopsis equivalent for the grasses. Its genome has recently been sequenced and microarrays as well as T-DNA mutants are available. IBERS holds one the largest collection of Brachypodium and this will be screened for differences in drought tolerance. Drought responses in selected accessions will be characterised using Brachypodium Affymetrix arrays, focusing on genes involved in cell wall biogenesis. In collaboration with DLF-Trifolium, allele variation for selected candidate genes will be determined amongst the accessions and correlated with drought tolerance. These alleles will be used by DLF-Trifolium to screen grass germplasm for integration into their breeding programmes. Gene expression and allele variations will be related to cell wall chemistry using established methods developed within our group including electrospray ionization-tandem mass spectrometry(n) and 2D NMR (6). Mechanistic links between candidate genes, cell wall chemistry and drought tolerance will be established using Brachypodium T-DNA mutants. Output & Impact: Grass crops must tolerate increasingly severe drought conditions to maintain agricultural production. Cell wall chemistry plays an important role in protecting plants from water-deficit stress but properties related to drought resistance remain uncharacterized especially in grasses. Using a multidisciplinary approach we will supply essential data for the development of food and energy crops better equipped for extreme environmental conditions. The integration of different methodologies will provide an excellent training opportunity for a PhD student. Given the importance of this research area, we expect the results to be published in high-impact journals. 1. Moore et al., (2008) Physiol Plantarum, 134, 237-245. 2. Bray, (2004) J Exp Bot, 55, 2331-2341. 3. Konno et al., (2008) J Plant Physiol, 165, 745-754. 4. Fan et al., (2006) Plant Physiol, 140, 603-612. 5. Hura et al., (2009) J Plant Physiol, 166, 1720-1733. 6. Parveen et al., (2008) Phytochemistry, 69, 2799-2806.