Gene and repetitive sequence annotation in the Triticeae

The Triticeae tribe contains some of the world’s most important agricultural crops (wheat, barley and rye) and is perhaps, one of the most challenging for genome annotation because Triticeae genomes are primarily composed of repetitive sequences. Further complicating the challenge is the polyploidy found in wheat and particularly in the hexaploid bread wheat genome. Genomic sequence data are available for the Triticeae in the form of large collections of Expressed Sequence Tags (>1.5 million) and an increasing number of bacterial artificial chromosome clone sequences. Given that high repetitive sequence content in the Triticeae confounds annotation of protein-coding genes, repetitive sequences have been identified, annotated, and collated into public databases. Protein coding genes in the Triticeae are structurally annotated using a combination of ab initio gene finders and experimental evidence. Functional annotation of protein coding genes involves assessment of sequence similarity to known proteins, expression evidence, and the presence of domain and motifs. Annotation methods and tools for Triticeae genomic sequences have been adapted from existing plant genome annotation projects and were designed to allow for flexibility of single sequence annotation while allowing a whole community annotation effort to be developed. With the availability of an increasing number of annotated grass genomes, comparative genomics can be exploited to accelerate and enhance the quality of Triticeae sequences annotation. This chapter provides a brief overview of the Triticeae genomes features that are challenging for genome annotation and describes the resources and methods available for sequence annotation with a particular emphasis on problems caused by the repetitive fraction of these genomes

A Toolbox for Triticeae Genomics

International audienceIn the last two decades, progress in cereal genomics has been remarkable, enabling a better understanding of the structure and function of the cereal genomes. However, significant advances mainly concerned rice and maize, whereas for the Triticeae species, namely wheat, barley and rye, the development of genomic tools and resources has long been hampered by the size and the complexity of their genomes. Recently, new technologies have allowed the development of a toolbox for Triticeae genomics comparable to what is available for rice and maize. Triticeae scientists and breeders can now benefit from a wide range of tools, including molecular markers, genetic maps, EST sequences, microrarrays, BAC libraries and transformation systems that can be applied to structural, functional, evolutionary and comparative genomic studies of the Triticeae genomes