The genetic material of eukaryotes is packed together with proteins into an elaborated structure, called the chromatin. Initially discovered as a colorable substance in cytological preparations, the chromatin is now known as a modular molecular complex which greatly influences gene expression. The challenge of the epigenetic field of research is to decrypt the different forms at the molecular, nano and microscale and detailed composition of chromatin states in relation to their function. Our research contributes to this challenge by exploring the role of specific chromatin architects, the linker histones.

Lay summary

Chromatin provides a tunable, molecular platform for controlling gene expression in eucaryotes. Biochemical modifications of the DNA and nucleosome histones are a major component of the epigenetic code. Besides, higher-order-level chromatin organization and in fine gene expression is also influenced by chromatin architects such as the linker histones (H1). Long thought to be only structural, the repertoire of H1 roles has been considerably extended in recent years, with for instance a central role in mammalian cells pluripotency. Plant cells like animal cells also comprise a complement of H1 variants but their function is far from being elucidated. Our research aim at elucidating the role of H1 in the model plant Arabidopsis particularly in relation to cellular reprogramming under developmental and environmental cues. For this, we are using a combination of genetic, molecular and cytological approaches and are focusing on two study cases involving H1 function: (i) the somatic-to-reproductive transition; (ii) transcriptional responses under diurnal light rythms. Collectively, we hope to shed light on the contribution of high-order chromatin organisation, mediated by H1, to general reprogramming processes underlying cellular responses and plasticity in plants.