The systems architecture of molecular memory in poplar after abiotic stress

Abstract

Throughout the temperate zones, plants face combined drought and heat spells in increasing frequency and intensity. We compared periodic (intermittent, i.e. high-frequency) versus chronic (continuous, i.e. high-intensity) drought-heat stress scenarios in Gray poplar (Populus x canescens) plants for phenotypic and transcriptomic effects during stress and recovery. Post-recovery photosynthetic productivity after stress exceeded the performance of poplar trees without stress experience. We analyzed the molecular basis of this stress-related memory phenotype and investigated gene expression responses across five major tree compartments including organs and wood tissues. For each of these tissue samples, transcriptomic changes induced by the two stress scenarios were highly similar during the stress phase but strikingly divergent after recovery. Characteristic molecular response patterns were found across tissues but involved different genes in each tissue. Only a small fraction of genes showed similar stress and recovery expression profiles across all tissues, among them protein phosphatases of type 2C, the LATE EMBRYOGENESIS ABUNDANT PROTEIN 4-5 genes and orthologs to the Arabidopsis thaliana transcription factor HOMEOBOX LEUCINE-ZIPPER PROTEIN 7. Predicted transcription factor regulatory networks for these genes suggest that a complex interplay of common and tissue-specific components contributes to the coordination of post-recovery responses to stress in woody plants.