Sequencing, Assembly and Characterization of a Transcriptome Resource for Brachypodium sylvaticum (Poaceae)

The perennial bunchgrass Brachypodium sylvaticum (slender false brome) is native to Europe, Asia, and North Africa, but is rapidly invading habitats in the Pacific Northwest and California. B. sylvaticum is closely related to the model grass B. distachyon. The recent invasion success and ongoing range expansion of false brome in a climate that is unique relative to its native habitats presents tremendous potential for genomic investigations in adaptation and invasive species biology. Here we report the de novo sequencing, assembly, and characterization of the transcriptomes of three different B. sylvaticum plants from the non-native population in Corvallis, Oregon (USA) and native populations of Spain and Greece. We obtained average contig lengths of 1,652 bp in the Corvallis sample, 1,728 bp in Spain, and 1,566 bp for samples from Greece. More than 90% of the B. sylvaticum contigs were annotated based on similarity to known genes or Genbank sequences. Moreover, comparative analysis of the three B. sylvaticum transcriptomes and B. distachyon revealed >90% overlap. We also functionally annotated >60% of the B. sylvaticum assemblies using Interproscan and assigned gene ontology terms using Blast2GO. We identified over 20,000 di-, tri-, tetra-, penta-, and hexa-nucleotide SSR markers amongst the three B. sylvaticum transcriptomes. Furthermore, we validated variable SSRs in several loci in the three B. sylvaticum populations and B. distachyon. Our results indicate that we have sequenced and assembled ~90% of the B. sylvaticum transcriptomes for three distinct populations. This transcriptome assembly and catalog of SSRs will be a significant resource for ecologists and geneticists conducting research on native and invasive populations of B. sylvaticum.