Epidermal cell type-specific chromatin dynamics underlying Arabidopsis heat stress memory

In the past decades, rising temperatures have negatively affected the distribution and yield of major crop species such as rice, maize, and wheat. This trend will continue in the future due to increased global warming. As sessile organisms, plants must cope with constant biotic and abiotic stress exposure and adapt their growth and development accordingly. In extreme cases, these adaptative processes also lead to stress responses. Most of these responses are transient physiological answers to intermediate stress, but plants also possess a memory potential to stay alert even if an unfavorable condition has already ceased. This memory is controlled by chromatin-based mechanisms and has been mainly studied in whole tissues or plants. However, as mixed cell populations can lead to an averaging effect of chromatin marks and dynamics, the experimental resolution and specificity become more apparent if mechanisms underlying stress memory are analyzed in a cell type-specific context. Stomata, the microscopic pores on the leaf epidermal surface of plants, are crucial to mitigate the otherwise harmful effects of higher temperatures. Therefore, deciphering the molecular mechanisms underlying stomatal stress responses is essential for understanding plants” ability to adapt to changing environmental conditions. To assess the transcriptional states and corresponding chromatin dynamics underlying heat stress (HS) memory effects in stomata and epidermal leaf cells, we have used flow cytometry to generate whole-genome chromatin accessibility and expression maps from stomatal and epidermal cells by assaying for transposase-accessible chromatin (ATAC) regions and the transcriptome via RNA-seq. We are also generating histone profiles for two specific histone modifications – activating H3K4me3 and repressing H3K27me3 – and are merging the information from the different omics approaches in combination with loss of function mutants of novel cell type-specific memory genes to better understand stress memory regulation in plants