Global epigenetic analysis revealed dynamic fluctuations in levels of DNA methylation and histone modifications in the calli of Fagopyrum with different capacity for morphogenesis

Abstract

Buckwheat characterises with high susceptibility to in vitro tissue culture conditions, which have been researched extensively to study a plethora of processes. F. tataricum morphogenic callus (MC) is characterised by its capacity for morphogenesis for up to ten years of culture, displaying an extraordinary level of genome stability, and comprises of proembryogenic cell complexes (PECC),which are the structures resembling somatic embryos arrested on the pre-globular stage. The non-morphogenic callus (NC) that appears on the surface of MC after approximately two years of culture due to endoreduplication cycles, is characterised by aneuploidy, rapid growth rate and high level of oxidative stress. F. esculentum embryogenic callus (EC) has different morphological and histological features, remains stable for up to three years of culture, has a dense, globular structure, and is capable of forming embryoids from the masses of embryogenic cells, but does not produce a non-embryogenic clone. In this work, immunocytochemical analyses revealed dynamic epigenetic changes in Fagopyrum calli. We demonstrated that; decreased level of H3K4me2 seems to be associated with pluripotency acquisition in F. esculentum EC and F. tataricum MC; DNA hypomethylation appears to be connected with the acquisition of the embryogenic potential and PECC reinitiation in F. tataricum MC. Moreover, we observed that H4K16ac and H4K5ac exhibited the highest variability during the course of passage in NC. Elevated levels of these modifications on day zero and day six for H4K16ac and H4K5ac, respectively, seem to be connected with endoreplication peaks, the processes which are characteristic of this callus.