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.
Highlights
Plants necessarily experience changes in temperature during their life cycle
The control of gene expression based on chromatin organization rather than on primary DNA sequence information is referred to as epigenetics [7]
A number of studies have shown that DNA methylation and histone posttranslational modifications play a key role in epigenetic control and plant functional status under stress (e.g. [4,6,8,10,11]) by controlling the functional state of chromatin and gene expression [12,13,14,15]
Summary
Plants necessarily experience changes in temperature during their life cycle. A diversity of cellular targets is greatly affected by atypically high temperatures that can induce a re-setting of physiological, biochemical and molecular programs and affect plant growth and performance [1,2,3]. [4,6,8,10,11]) by controlling the functional state of chromatin and gene expression [12,13,14,15] These epigenetic marks are generated fast, can be transmitted across cell divisions (meiotically and mitotically) and can be reversed, providing a way to confer plasticity in the plant response and temporary ‘‘memory’’ strategies [8,16]. Experiments inquiring this subject in Arabidopsis showed that prolonged heat stress (37uC, 42uC) induces a transient release of gene silencing [17,18], but once a plant is removed from stress, gene expression is re-established within 48 hours
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