Brachypodium as a Model System for Studying Monocot Virus:Host Interactions

Plants respond to pathogens using elaborate networks of genetic interactions.  Yet there are substantial gaps in our knowledge regarding host:virus interactions, especially in grasses and cereals. Towards elaborating these responses we have initiated studies using Brachypodium distachyon, as a model C3 grass, to study molecular responses of a host to virus infection. For this we have used Brachypodium Bd21-3 plants infected with Panicum mosaic virus (PMV) to build a transcriptome map based on microarray and RNA-seq analyses bolstered by biochemical and microscopic analyses of the effects of the virus on host defenses. We selected thirteen marker defense-related genes associated with JA, SA, and ET signaling pathways that are altered in PMV-infection, and have investigated their expression and regulation by qRT-PCR analyses. Six additional, unrelated viruses were used for comparative studies of Brachypodium and Setaria italica, a C4 grass. We have found, with some exceptions, substantial conservation of gene expression responses not only to the viruses we tested, but also toward known biotrophic (fungi and bacteria) infections of Arabidopsis. To develop an integrated model of host responses to pathogen infection, we are exploring meaningful parallels between effector-triggered and pathogen-triggered responses to plant viruses in C3 and C4 grasses. These discoveries may lead to new strategies to develop plants broadly resistant to diverse viruses and other plant pathogens.