DNA Methylation in Acacia mangium In vitro and Ex-vitro Buds, in relation to their Within-shoot Position, Age and Leaf Morphology of the Shoots

Abstract

Abstract DNA methylation was analyzed in Acacia mangium Willd. buds collected from in vitro and field growing shoots from the same clone and its juvenile offspring. Shoot tips from in vitro microshoots showed higher levels of DNA methylation for juvenile (23.4%) than for mature (21.8%) plant material, irrespective of their morphology. Likewise, under the same in vitro conditions, the apical buds collected from microshoots exhibiting the juvenile morphology displayed higher DNA methylation rates (23.2%) than those characterized by the mature phyllode morphological type (22.1%), regardless of the age of the plant material source. In outdoor conditions, apical buds collected from mature tree growing shoots were significantly less methylated (20.9%) than the resting axillary buds located just underneath (25.2%) and than the apical buds from the in vitro microshoots of the same clone and mature-like phyllode morphology (22.6%). Overall, the DNA methylation levels found for our Acacia mangium plant materials were consistent with those reported for other Angiosperms, but showed, similarly to other recent findings in different species, that DNA methylation in plants does not always increase with ageing. This was discussed in relation to other phase-related traits and more particularly foliage characteristics, which are conspicuous markers of ageing in this heteroblastic species.