Abstract
Although several linker histone variants have been studied in both animal and plant organisms, little is known about their distribution during processes that involve alterations in chromatin function, such as differentiation, dedifferentiation and hormone treatment. In this study, we identified linker histone variants by using specific anti-histone Hl antibodies. Each variant's ratio to total Hl in the three developmental zones of maize (Zea mays L.) root and in callus cultures derived from them was estimated in order to define possible alterations either during plant cell differentiation or during their dedifferentiation. We also evaluated linker histone variants' ratios in the developmental zones of maize roots treated with auxin in order to examine the effects of exogenous applied auxin to linker histone variant distribution. Finally, immunohistochemical detection was used to identify the root tissues containing each variant and correlate them with the physiological status of the plant cells. According to the results presented in this study, linker histone variants' ratios are altered in the developmental zones of maize root, while they are similar to the meristematic zone in samples from callus cultures and to the differentiation zone in samples from roots treated with auxin. We propose that the alterations in linker histone variants' ratios are correlated with plant cell differentiation and dedifferentiation.
Highlights
The primary level of DNA compaction into the chromatin of eukaryotic cells is the nucleosome, where 146bp of DNA are wrapped around a histone octamer core, comprised of two of each histones, H2A, H2B, H3 and H4, while its structure is completed with the association of H1 linker histone (Wolffe and Guschin, 2000)
Several liliaceous plants specific histone H1 variants appear during male meiosis (Ueda and Tanaka, 1995), other variants expressed during water deficit have been identified in several monocots and dicots (Scippa et al, 2004) whereas a specific H1 variant has been found to localize in nucleoli of higher plant cells (Tanaka et al, 1999)
Callus cultures were developed from root segments, representing the three developmental zones, which were placed under aseptic conditions in glass tubes containing sterilized Murashige and Skoog medium (Murashige and Skoog, 1962) that was supplemented with 1 mg.L-1 2,4dichlorophenoxyacetic acid (Sigma) and 3% (w/v) sucrose and solidified with 0.5% (w/v) agar
Summary
The primary level of DNA compaction into the chromatin of eukaryotic cells is the nucleosome, where 146bp of DNA are wrapped around a histone octamer core, comprised of two of each histones, H2A, H2B, H3 and H4, while its structure is completed with the association of H1 linker histone (Wolffe and Guschin, 2000). Linker H1 histones have been found to display greater variability when compared to core histones (Brown, 2001). This heterogeneity is conserved between eukaryotes, suggesting that individual H1 variants may have unique properties, resulting in specific roles in chromatin function (Cole, 1987, Zlatanova et al, 2000). In several liliaceous plants specific histone H1 variants appear during male meiosis (Ueda and Tanaka, 1995), other variants expressed during water deficit have been identified in several monocots and dicots (Scippa et al, 2004) whereas a specific H1 variant has been found to localize in nucleoli of higher plant cells (Tanaka et al, 1999)
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