Transcriptome Changes During Cold Acclimation in Festulolium and Their Comparison to Festuca pratensis and Lolium perenne Genomes

Festulolium (F. pratensis x L. perenne) is one of the main forage grass species utilized in temperate agricultural regions due to its high quality ryegrass and resistance to hostile environments. However, during late winter and early spring, plants are particularly vulnerable to winter injury. De-hardening resistance and re-hardening capacity plays a significant role in determining winter survival. Understanding these mechanisms is important for developing cultivars with improved winter survival. We have studied global transcriptome changes during a cycle of hardening, de-hardening and re-hardening, the relationship with freezing tolerance and interactions with vernalization in two genotypes from Festulolium candivar FuRs9806; one flower without vernalization (V-) and one need vernalization to flower (V+). The LT₅₀ results showed that vernalization at +6 ºC led to higher frost tolerance than pre-treatment at +15 ºC. The V+ genotype vernalized at +6 ºC showed the largest capacity to re-harden (3-6 ºC) thus showing a significant difference between the two genotypes possibly linked to different vernalization requirements. Illumina paired end sequencing yielded 296 and 242 million reads for the V- and V+ genotypes, respectively. These reads were assembled into 332059 and 262382 transcripts with average contig lengths of 1570 and 1414 bp for the V- and V+ genotypes, respectively. In total, 9730 and 3530 significantly differentially expressed genes with FDR<0.01 were detected in V- and V+ genotypes, respectively. These genes include the vernalization genes, stress responsive genes involved in cold-response, cold sensing, signal transduction and osmo-sensing. Detailed global transcriptome changes affected by vernalization, hardening and de-hardening, will be presented. In addition, De Novo sequencing of Festuca pratensis genome performed by Illumina mate pair sequencing will be presented along with Festuca genome and synteny browsers. Furthermore, we used BLAST to search sequence similarities between our Trinity assembled Festulolium contigs to the Lolium perenne and Festuca pratensis genome sequences.