The tissue-specific chromatin accessibility landscape of Papaver somniferum

Accessible chromatin regions (ACRs) at promoters, enhancers, and other gene regulatory regions allow transcription factors (TFs) to bind, which regulate gene transcription involved in plant development and metabolism. Papaver somniferum has been widely applied in clinical medicine as one of the most important and oldest medicinal plants due to its unique and effective active ingredients. However, the transcriptional regulatory mechanism of tissue-specific distribution of active ingredients remains unknown. In this study, transcriptome and chromatin accessibility analysis by RNA sequencing (RNA-seq) and assay for transposase-accessible chromatin sequencing (ATAC-seq) was performed to investigate these underlying molecular mechanisms. We identified tissue-specific chromatin Tn5 hypersensitive site (THS) and gene expression by examining the variation of THS and transcripts across six tissues (capsule, stem, fine root, tap root, leaf, and petal). Our results provide insight into the epigenetic mechanism of transcriptional plasticity for P. somniferum organ development. Sequence motif analysis within accessible chromatin regions for co-expressed gene modules revealed enriched binding sites of hub transcription factors that regulate tissue-specific functions. Furthermore, we identified regulatory elements for tissue-specific accumulation of morphine and noscapine in P. somniferum . This is the first tissue-specific chromatin accessibility landscape of P. somniferum providing an important resource for functional epigenetic analysis and future molecular breeding in P. somniferum for variety improvement. ### Competing Interest Statement The authors have declared no competing interest.