Panicum mosaic virus and its satellites in grasses
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In the United States, viable bioenergy and grain production is considered crucial to the health, security, and economic growth of the nation. However, there is an under-realized issue in growing maize, switchgrass, and bioenergy crops built grasses. These plants are hosts to a plethora of plant pathogens, including plant viruses. . In general, grasses have been relatively neglected in laboratory studies of host-virusinteractions. To study these interactions experimental (model) plants such as Brachypodium distachyon (Brachypodium) are used to limn the fundamental controls that determine disease outcomes (5-8). More specifically genes, proteins, metabolites, and higher order regulatory networks essential for biological homeostasis may be useful in crop applications.Understanding these relationships in plants facing biotic and abiotic stresses will provide a critical firststep towards designing practical strategies to mitigate the resulting crop losses. We have pioneered the use of systems biology approaches to dissect the molecular perturbations in plant cells infected with Panicum mosaic virus (PMV) (7, 9, 10).PMV was first reported in switchgrass in 1957, and was subsequently identified as the causal agent for St. Augustinegrass decline disease in the southern United States (11, 12). Today, PMV threatens switchgrass breeding programs aimed for biofuel production with upwards of 75% of fields tested positive for PMV (13). Despite deployment of PMV-tolerant varieties, PMV is ubiquitous in St. Augustinegrass lawns throughout Texas (1, 2). PMV is a helper virus, supporting replication and movement of a satellite virus (SPMV) and satellite RNAs (satRNA) (3, 4, 10-12, 14-23). SPMV and satRNA can be supported in co-infections with PMV alone, or as a three component complex of PMV+SPMV+satRNA (3, 4).Host:virus interactions. Using Brachypodium and green millet (Setaria viridis), we have identified interactions associated with elicitation of plant immune responses towards understanding strategies used by viruses to target host-defenses--strategies that may be future targets for engineering resistance or tolerance in crop plants. Using transcriptomic (tiling array and RNAseq) and metabolomic (LC-MS/GC-MS) techniques, we discovered key defense gene networks and metabolites involved in salicylic acid (SA), jasmonic acid (JA) and ethylene (ET) signaling in PMV-infected Brachypodium (7, 10)..........