NATGRAIN · Grain development in Brachypodium distachyon

Grain development in Brachypodium distachyon

A small wild grass, Brachypodium distachyon, has recently emerged as a new experimental model (Opanowicz et al., 2008), providing an opportunity to genetically dissect how grain size is controlled. Brachypodium grain seems very similar to those of wheat and barley but its development and structure had not been carefully studied. However, its short life cycle and ease of cultivation under laboratory conditions and a fully sequenced genome make it an attractive genetic model system for understanding the genetic basis of biological processes in related grasses and cereals. The overall aim of this project has been to exploit natural and induced variation to understand grain development in this species. The project objectives were: 1. Document developmental stages of grain development at the cellular and molecular level. 2. Define the extent of natural variation in grain shape and size. 3. Determine genetic basis of grain variation in Brachypodium. To achieve these objectives, grain development was extensively characterised first using the reference strain, Bd21, an accession collected from Iraq. Grain development was characterised at various levels (i.e. morphological, cellular and molecular) using plant material grown in a defined controlled environment. Subsequently, grain development has been surveyed in mutant and natural accessions collected from different regions in Europe and the Middle East and selected natural accessions used to create mapping populations that will allow identification of genes that influence grain size and shape. The first detailed description of grain development in a wild grass, which has been published as a peer-reviewed paper in the Journal of Experimental Botany (Opanowicz et al 2011). The first detailed description of a mutant affecting grain development in Brachypodium, published in the Plant Journal (Vain et al, 2011). Impact: demonstrates the potential that Brachypodium has as a model system to dissect numerous aspects of grass developments, and the comparison with Arabidopsis illustrates its utility for functional analysis of evolutionary differences between monocotyledonous and dicotyledonous plants. Mapping populations of Brachypodium suitable for the identification of gene underlying key traits, not restricted to grain traits but including disease resistance and drought tolerance. Impact: these populations will be available to the community for research on a variety of topics and are already being used by other laboratories. Identification of key sites with mixed populations of diploid and alleoploid plants that should allow us to address questions of adaptation and the significance of ploidy variation in the grasses. Impact: the tendency of plants to alter their DNA content, especially by interspecies hybridisation, is believed to be a major factor in domestication of many species as it is often associated with increased size, more rapid growth or increased stress tolerance, but its role in the natural environment can only be speculated on.

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