Transgenerational responses to Pseudomonas infection in Arabidopsis

Research on plant immune responses to bacterial pathogens has been complicated by two revelations of the high-throughput sequencing era of plant biology: (1) Microbiome sequencing has revealed that plants are frequently infected by multiple pathogens simultaneously. Controlled lab studies show that the defense systems activated by different pathogens may even antagonize each other via hormonal crosstalk. Thus, an understanding of how co-infection differs from the single infections typically studied in the lab is essential for translating knowledge of plant immunity to field settings. (2) Epigenetic marks on plant genomes are altered by pathogen infection and these changes can be transmitted to offspring, meaning that offspring plant immune responses can depend upon, or be primed by, parental infections. Knowledge of the pervasiveness and duration of priming is necessary to understand how plant immunity works in real populations.To study the effects of co-infection on transgenerational defense priming in the model plant Arabidopsis thaliana, we generated plant lineages with different histories of single- and multi-pathogen infections across generations and collected leaf tissue from parental and offspring plants for transcriptome sequencing (mRNA-seq). We considered two bacterial pathogens isolated from natural A. thaliana populations: Pseudomonas syringae (Michigan strain NP29.1A) and Pseudomonas viridiflava (Michigan strain RMX3.1B). With the RNA-seq libraries, we aim to compare the loci where expression is primed by simultaneous infection as opposed to single infections. We considered two A. thaliana genotypes (Col-0 and Are-0) in order to understand how natural genetic variation affects transcriptional responses to multiple infections.