Abstract
Microscopic studies of young needles and shoot tips fromTaxus baccatashowed that flavanols are localized in the nuclei. This observation is based on the histochemical staining of flavanols with the DMACA reagent. The colour that is obtained with this reagent varies from pale to deep blue, depending on the amount of flavanols. This study is focused on nondifferentiated cell lineages and on differentiating cells. The key point to note is that all nuclei of a cell lineage showed a uniform DMACA staining pattern based on the amount and structural appearence of nuclear flavanols. This points to transcriptional and epigenetic programming. However, comparing various cell lineages from different shoot tips and needles revealed a lineage-specific expression of nuclear flavanols. This result implied that both positional and developmental signals from neighbouring cells were involved in the nuclear flavanol binding of lineages. The cells of a developmentally advanced lineage loose their intimate contact and, then, they separate from each other to undergo an autonomous, individual sequence of differentiation. This in turn was accompanied by differences in the nuclear flavanol patterns of the single cells. Investigating different mitotic stages revealed a wide spectrum in flavanol staining intensities of the chromosomes. These observations should be linked to UV-VIS spectroscopical kinetic results indicating that nuclear flavanols bound to histones are involved in epigenetically regulated modification of chromatin. The kinetic studies show that catechin is relatively rapidly degraded by oxygen in the presence of -ions. However, this degradation reaction is strongly inhibited when histone proteins were added. This behaviour is a clear indication that coregulatory interactions exist between catechin and histones.
Highlights
Trees of Taxus baccata are rich in flavonoids and make use of them as defense compounds against pathogens (Kim et al [1])
Leaf lineages are induced by signaling molecules moving from the centre of a shoot apex into the lateral cell layers of the apical dome which form leaf primordia (Lenhard and Laux [14])
As outlined by Mauseth [15], a packet of a recently formed cell lineage can act as a physiological unit
Summary
Trees of Taxus baccata are rich in flavonoids and make use of them as defense compounds against pathogens (Kim et al [1]). A special subgroup of flavonoids are the flavanols. In previous studies it was shown that commercial histones have the potential to associate with flavanols (Polster et al [2], Feucht et al [3]). It is assumed that Taxus histones bind to flavanols. With the aid of microlaser dissection techniques and UV visible spectroscopic titration, it could be established that flavanols are genuinely present in conifer nuclei (Polster et al [4]). This agrees with a recent communication that starter enzymes of the flavonoid pathway, that is, chalcone synthases, were found to be located in nuclei of Arabidopsis (Saslowsky et al [5]). Hutzler et al [6] previously detected yellow fluorescing flavonoids in nuclei using microscopy
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