De Novo Assembly and Characterization of Tall Fescue Transcriptome under Water Stress.

Water stress is a fundamental problem for tall fescue [Lolium arundinaceum (Schreb.) Darbysh.] cultivation in the south-central United States. Genetic improvement of tall fescue for water-stress tolerance is the key strategy for improving its persistence in the region. Genotypes with contrasting characteristics for relative water content and osmotic potential were identified from a tall fescue population. Transcriptome profiling between water-stress-tolerant (B400) and water-stress-susceptible (W279) genotypes was performed to unravel the genetic regulatory mechanism of water-stress responses in tall fescue. RNA samples from leaf, shoot, root, and inflorescence were pooled and sequenced through Illumina paired-end sequencing. A total of 199,399 contigs were assembled with an average length of 585 bp. Between the two genotypes, 2986 reference transcripts (RTs) were significantly differentially expressed and 1048 of them could be annotated and found to associate with metabolic pathways and enzyme coding genes. In total, 175 differentially expressed RTs were reported for various stress-related functions. Among those, 65 encoded kinase proteins, 40 each encoded transposons, and transporter proteins were previously reported to be involved with abiotic stress responses. A total of 6348 simple sequence repeats and 6658 single-nucleotide polymorphisms were identified in the contig sequences. Primers were developed from the corresponding sequences, which might be used as candidate gene markers in tall fescue. This study will lead to identification of genes or transcription factors related to water-stress tolerance and development of a comprehensive molecular marker system to facilitate marker-assisted breeding in tall fescue.