Cellular and Molecular Characterisation of Senescence in the energy grass Miscanthus

Supervisor: Dr Iain Donnison

The Institute is one of the participants in the Biomass, Biofuels and Energy Crops consortium funded by the EPSRC SuperGen initiative (http://www.supergen-bioenergy.net/) and this project is funded by this grant.

There are very ambitious targets for reductions in carbon dioxide emissions and the use of renewable energy which need to be achieved in the near to medium term. Biomass crops are seen as having the potential to make a major contribution to achieving these targets particularly for liquid transport fuels. Energy grasses such as Miscanthus are highly promising biofuel crops because they are high yielding with low inputs, e.g. of energy demanding nitrogen fertiliser, and therefore more sustainable in the long term than first generation energy crops. For example field plots of Miscanthus can frequently require no nitrogen inputs for up to 7-8 years. This is because Miscanthus stems are conventionally harvested dry once senescence is complete and a combination of the highly efficient remobilisation of resources to the rhizome (below ground storage organ) and subsequent leaching during the winter means that very little nitrogen is removed from the field. Most plant nitrogen is contained within proteins; furthermore, approximately 30% of the leaf protein is associated with chlorophyll which, during senescence, needs to be degraded and remobilised. However unbound chlorophyll is highly photoreactive and has to be rapidly catabolised once the associated proteins are broken down. The loss of chlorophyll and therefore green colour is a functional marker for senescence and is a familiar sight every Autumn. Senescence with co-ordinated protein and chlorophyll breakdown is different to rapid cell death caused by a dramatic end to the growing season for example as caused by early season frosts. The ability to mobilise resources via senescence before cell death processes occur is an important goal for sustainable energy crop production. The proposal is therefore to make a cellular and molecular study of senescence in Miscanthus following natural senescence and compare this to a more rapid cell death. The Institute has previously studied natural and induced senescence in a number of grasses and therefore has built up a suite of gene and protein based markers which can be applied to Miscanthus to determine the fate of nitrogen during senescence. Early and late senescing genotypes identified from genetic resources within the UK Miscanthus breeding programme, also based at IBERS, will be used to study senescence and to develop the ability to optimise resource utilisation in this important energy crop.