RNA-seq analysis of Brachypodium distachyon responses to Barley stripe mosaic virus infection

Barley stripe mosaic virus (BSMV) is the type member of the genus Hordeivirus. Brachypodium distachyon line Bd3-1 shows resistance to the BSMV ND18 strain, but is susceptible to an ND18 double mutant (β NDTGB1R390K, T392K) in which lysine is substituted for an arginine at position 390 and for threonine at position 392 of the triple gene block 1 (TGB1) protein. In order to understand differences in gene expression following infection with ND18 and double mutant ND18, Bd3-1 seedlings were subjected to RNA-seq analyses at 1, 6, and 14days post inoculation (dpi). The results revealed that basal immunity genes involved in cellulose synthesis and pathogenesis-related protein biosynthesis were enhanced in incompatible interactions between Bd3-1 and ND18. Most of the differentially expressed transcripts are related to trehalose biosynthesis, ethylene, jasmonic acid metabolism, protein phosphorylation, protein ubiquitination, transcriptional regulation, and transport process, as well as pathogenesis-related protein biosynthesis. In compatible interactions between Bd3-1 and ND18 mutant, Bd3-1 developed weak basal resistance responses to the virus. Many genes involved in cellulose biosynthesis, protein amino acid phosphorylation, protein biosynthesis, protein glycosylation, glycolysis and cellular macromolecular complex assembly that may be related to virus replication, assembly and movement were up-regulated. Some genes involved in oxidative stress responses were also up-regulated at 14dpi. BSMV ND18 mutant infection suppressed expression of genes functioning in regulation of transcription, protein kinase, cellular nitrogen compound biosynthetic process and photosynthesis. Differential expression patterns between compatible and incompatible interactions in Bd3-1 to the two BSMV strains provide important clues for understanding mechanism of resistance to BMSV in the model plant Brachypodium.