Revealing the Molecular and Physiological Responses to Water Deficit in the Bioenergy Crop Miscanthus x giganteus

High yielding perennial biomass crops of the species Miscanthus are widely recognized as one of the most promising lignocellulosic feedstocks for the production of bioenergy and bioproducts. Miscanthus is a C4 grass and thus has relatively high water use efficiency. Cultivated Miscanthus comprises primarily of a single clone, Miscanthus x giganteus, that is high yielding and expresses many desirable traits required in an ideal biomass crop; however, it responds poorly to low water availability. Despite this, we have little knowledge of the mechanisms involved in the drought response and recovery from drought in M. x giganteus. To address this, we are implementing integrative approaches, combining physiological, genetic and metabolic analysis, using M. x giganteus plants exposed to water-deficit stress in pot experiments. Withholding water resulted in marked changes in plant physiology with growth-associated traits among the first affected, the most rapid response being a decline in the rate of stem elongation followed by a reduction in photosynthetic performance. Determining the ability of the plants to regrow after a period of water deficit has enabled identification of the critical drought point of the rhizome and given further insight into the balance between withstanding water deficit and biomass accumulation. Leaf tissue samples were taken at key drought stages (intermediate and terminal) for RNA sequencing analysis and metabolite profiling. These analyses identified metabolites and genes associated with drought and provide potential targets for improved drought-tolerance of the Miscanthus bioenergy crop.