Abstract
Epigenetic modifications of chromatin structure are essential for many biological processes, including growth and reproduction. Patterns of DNA and histone modifications have recently been widely studied in many plant species, although there is virtually no data on the spatial and temporal distribution of epigenetic markers during plant development. Accordingly, we have used immunostaining techniques to investigate epigenetic modifications in the root apical meristem of Hordeum vulgare. Histone H4 acetylation (H4K5ac), histone H3 dimethylation (H3K4me2, H3K9me2) and DNA methylation (5mC) patterns were established for various root meristem tissues. Distinct levels of those modifications were visualised in the root cap, epidermis, cortex and vascular tissues. The lateral root cap cells seem to display the highest level of H3K9me2 and 5mC. In the epidermis, the highest level of 5mC and H3K9me2 was detected in the nuclei from the boundary of the proximal meristem and the elongation zone, while the vascular tissues were characterized by the highest level of H4K5ac. Some of the modified histones were also detectable in the cytoplasm in a highly tissue-specific manner. Immunolocalisation of epigenetic modifications of chromatin carried out in this way, on longitudinal or transverse sections, provides a unique topographic context within the organ, and will provide some answers to the significant biological question of tissue differentiation processes during root development in a monocotyledon plant species.
Highlights
One of the most intensively studied tissues in higher plants is the root apical meristem (RAM), which contains stem cells [1,2,3]
Histone H4 acetylation at lysine 5 (H4K5ac) The levels of H4K5ac were measured in 1,953 nuclei, which comprised the distal meristem, proximal meristem and the boundary between the proximal meristem and elongation zone
The highest level of this modification in the meristem was detected in vascular tissues and perycycle (Figure 2B, 2C, 2G, 2I, 2L and 2M), contrary to the epidermis (Figure 2C and 2H) and root cap (Figure 2A, 2E, 2F and 2L), which were the lowest
Summary
One of the most intensively studied tissues in higher plants is the root apical meristem (RAM), which contains stem cells [1,2,3]. In a transverse section of a Hordeum vulgare meristem five main types of tissues can be distinguished, i.e. a layer of the epidermis, four layers of the cortex, a layer of the endodermis, a layer of the pericycle and vascular tissues (stele) (Figure 1B). The latter has a constant number of eight cells of protophloem to one central cell of the metaxylem.
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