[Show abstract][Hide abstract] ABSTRACT: Cork oak (Quercus suber L.) is a research priority in the Mediterranean area and because of cork oaks’ distribution these stands are experiencing daily stress. Based on projections of intensifying climate change and considering the key role of exploring the recovery abilities, cork oak seedlings were subjected to a cumulative temperature increase from 25 °C to 55 °C and subsequent recovery. CO2 assimilation rate, chlorophyll fluorescence, anthocyanins, proline and lipid peroxidation were used to evaluate plant performance, while the relative abundance of seven genes encoding for proteins of cork oak with a putative role in thermal/stress regulation (POX1, POX2, HSP10.4, HSP17a.22, CHS, MTL and RBC) was analyzed by qPCR (quantitative Polymerase Chain Reaction). A temperature change to 35 °C showed abundance alterations in the tested genes; at 45 °C, the molecular changes were associated with an antioxidant response, possibly modulated by anthocyanins. At 55 °C, HSP17a.22, MTL and proline accumulation were evident. After recovery, physiological balance was restored, whereas POX1, HSP10.4 and MTL abundances were suggested to be involved in increased thermotolerance. The data presented here are expected to pinpoint some pathways changes occurring during such stress and further recovery in this particular Mediterranean species.
[Show abstract][Hide abstract] ABSTRACT: Trees necessarily experience changes in temperature, requiring efficient short-term strategies that become crucial in environmental change adaptability. DNA methylation and histone posttranslational modifications have been shown to play a key role in both epigenetic control and plant functional status under stress by controlling the functional state of chromatin and gene expression. Cork oak (Quercus suber L.) is a key stone of the Mediterranean region, growing at temperatures of 45°C. This species was subjected to a cumulative temperature increase from 25°C to 55°C under laboratory conditions in order to test the hypothesis that epigenetic code is related to heat stress tolerance. Electrolyte leakage increased after 35°C, but all plants survived to 55°C. DNA methylation and acetylated histone H3 (AcH3) levels were monitored by HPCE (high performance capillary electrophoresis), MS-RAPD (methylation-sensitive random-amplified polymorphic DNA) and Protein Gel Blot analysis and the spatial distribution of the modifications was assessed using a confocal microscope. DNA methylation analysed by HPCE revealed an increase at 55°C, while MS-RAPD results pointed to dynamic methylation-demethylation patterns over stress. Protein Gel Blot showed the abundance index of AcH3 decreasing from 25°C to 45°C. The immunohistochemical detection of 5-mC (5-methyl-2'-deoxycytidine) and AcH3 came upon the previous results. These results indicate that epigenetic mechanisms such as DNA methylation and histone H3 acetylation have opposite and particular dynamics that can be crucial for the stepwise establishment of this species into such high stress (55°C), allowing its acclimation and survival. This is the first report that assesses epigenetic regulation in order to investigate heat tolerance in forest trees.
PLoS ONE 01/2013; 8(1):e53543. DOI:10.1371/journal.pone.0053543 · 3.53 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Genes constitute only a small portion of the total genome and precisely controlling their expression represents a substantial
problem for their regulation. Furthermore, non-coding DNA, that contains introns repetitive elements and active transposable
elements, demands effective mechanisms to silence it long-term. Cell differentiation and development are controlled through
temporal and spatial activation and silencing of specific genes. These patterns of gene expression must remain stable for
many cell generations and last or change when inductive developmental signals have disappeared or new ones induce new programmes.
What turns genes on and off? Among others, gene regulation is controlled by epigenetic mechanisms, defined as any gene-regulating
activity that does not also involve changes in the DNA code and is capable of persisting. It has become apparent that epigenetic
control of transcription is mediated through specific states of the chromatin structure. Associations of specific chromosomal
proteins, posttranslational histone modifications and DNA methylation are some of the epigenetic mechanisms that are involved
in controlling chromatin states. DNA methylation research can be approached from several standpoints, since there is a wide
range of techniques available to study the occurrence and localisation of methyldeoxycytosine in the genome. Several studies
dealing with DNA methylation in relation to tree development, microproprogation and somaclonal variation will be presented,
with the final aim of demonstrating that DNA methylation levels are hallmarks for growing seasonal periods and are related
to open windows of competence in plants.
Plant Cell Tissue and Organ Culture 04/2007; 91(2):75-86. DOI:10.1007/s11240-007-9262-z · 2.61 Impact Factor