Transcriptomic basis for reinforcement of elm anti-herbivore defense mediated by insect egg deposition

In this study we applied RNA-sequencing to a set of larvae-challenged elm trees that had either been untreated before or been exposed to prior egg deposition by elm leaf beetles. This dataset allowed us to characterize the global transcriptional response of egg-primed and non-primed elm trees at different time points after the priming stimulus itself and after the onset of larval feeding. Overall design: At time point 0 of the experiment, elm leaves were treated with simulated egg deposition (compare Austel et al. 2015, Plant, Cell & Environment). Leaf material was harvested at 1hr, 6hrs and 24hrs after simulated egg-deposition (priming stimulus) from treated (P) and control samples (C) in triplicates. These samples are refered to as priming set (2 treatments P, C x 3 time points x 3 replicates = 18 samples). To obtain leaf tissue with larval feeding damage (triggering stimulus), neonate larvae were placed 7 days after the onset of the experiment onto plants with or without prior simulated egg deposition. Seven days match the egg incubation time until larvae would hatch. For the triggering set, leaf samples were taken in triplicates at 1hr, 6hrs and 24hrs after larval feeding from leaves with or without prior simulated egg-deposition in a full factorial design (i.e. control [CC], primed [PC], triggered [CT] and primed+triggered [PT ]) The triggering set is thus comprised of 36 samples in total (4 treatments x 3time points x 3 replicates).