Transcriptional memory of tomato plants using ultrasound and drought stress stimuli [WGBS]

Plant memory is a tool for plants that they can use to increase their fitness and cope with adverse environmental stresses. In this study, mRNA-seq., WGBS and RT-qPCR methods were applied for evaluating formation and maintenance of somatic transcriptional memory after treatment with ultrasound and drought stimuli in tomatoes. In addition, effects of repeated stimuli, as well as association-forming ability of plants were studied when they were trained previously with combined stimuli. 48 h after exposure to the two stimuli applied alone or in combination, significantly altered gene transcription and DNA methylation were revealed but there was no correlation between these changes. Using four selected target genes, we have proven that plants memorized stimuli for 5 to 10 days, in a gene-, and stimulus-dependent way. The repeated application of the stimuli caused altered behavior, such as habituation, sustained induction or modified re-induction, depending on the genes and physiological ages of plants. Plants were able to use one conditioned stimulus as a predictor of the other, unconditioned one, after conditioning in the case of 3 out of 4 target genes, and use their transcriptional memory associatively. Overall design: Two stimuli were applied in the experiments, ultrasound and drought stress, separately and in combination. They were applied at the onset of the experiments (initial stimuli; Treatment I), and then 5 and 10 days after the initial stimuli in the first and the second series of experiments (Treatment II), respectively. Changes in gene transcription and DNA methylation in response to US, D and US+D treatments 48 h after the treatments were investigated.