RNAi suppression of DNA methylation affects the drought stress response and genome integrity in transgenic poplar

Trees are long-lived organisms that continuously adapt to their environments, a process in which epigenetic mechanisms likely play key role. Via downregulation of the chromatin remodeler DECREASED IN DNA METHYLATION 1 (DDM1) poplar (Populus tremula × Populus alba) RNAi lines, we examined how methylation coordinates genomic and physiological responses moderate water deficit. We compared growth drought response two RNAi-ddm1 lines wild-type (WT) trees under well-watered deficit/rewatering conditions, analyzed methylomes, transcriptomes, mobilomes phytohormone contents shoot apical meristem. The were more tolerant drought-induced cavitation but did not differ height or stem diameter growth. About 5000 differentially methylated regions consistently detected both colocalizing with 910 genes 89 active transposable elements. Under deficit 136 expressed found, including many involved pathways; changes concentrations also detected. Finally, combination hypomethylation led mobility Our findings suggest major roles for regulation hormone-related stress responses, maintenance genome integrity through repression