Dipartimento di Biologia, Ecologia e Scienze della Terra

Now showing 1 - 2 of 2

Impact of DNA methylation on plant growth and development: a study on a methylation-defective mutant of Arabidopsis thaliana
(2017-06-09) Forgione, Ivano; Bruno, Leonardo; Van Lijsebettens, Mieke
Epigenetic modifications of DNA contribute to chromatin remodeling process and gene expression regulation playing a relevant role on the development of eukaryotic organisms. DNA methylation is an important epigenetic mark consisting in the addition of a methyl group on cytosine bases, which is observed in most of the organisms at the different evolution levels. In plants, DNA methylation is controlled by several genetic pathways, encoding different methyltransferases which act on different sequence contexts. Targets for cytosine DNA methylation in plant genomes are CG, CHG and CHH (H is A, T, C) sequences. The plant DNMT1-homolog METHYLTRANSFERASE1 (MET1) maintains DNA methylation at CG sites, whereas the DNMT3 homolog DOMAINS REARRANGED METHYLASE 1 and 2 (DRM1 and DRM2) are responsible for the de novo methylation in all sequence contexts. In addition, the plant-specific CHROMOMETHYLASE3 (CMT3) is responsible for DNA maintenance methylation at CHG sites, as well as at a subset of CHH sites. In plants DNA methylation is involved in diverse biological processes. Loss of methylation in the Arabidopsis thaliana mutants met1 and ddm1 (decrease in DNA methylation 1) causes several developmental abnormalities. Similarly, combined mutations in the DRMs and CMT3 genes induce pleiotropic defects in plants. Here, we used the Arabidopsis thaliana triple mutant drm1 drm2 cmt3, defective in DNA methylation to get deeper insight into the correlation between DNA methylation and plant growth. We identified novel developmental defects of the triple mutant dealing with the agravitropic response of the root and an altered differentiation pattern of the leaf which also exhibits a curly shape. Confocal microscopy of mutant transgenic lines expressing DR5:GFP reporter gene allowed us to verify that the loss of DNA methylation impacts on the accumulation and distribution of auxin from embryo to adult plant. The expression of auxin-related genes has been also found to be altered in drm1 drm2 cmt3 mutant. Furthermore, through an optimized and implemented protocol of comparative analysis of genomic methylated regions based on MeDIP-qPCR, we provide evidence about the direct and organ-specific modulation of auxin-related genes through DNA methylation process. The epigenetic mechanisms interplay with each other rather than work independently to modulate gene function. Accordingly, in our study we provide a novel evidence of the crosstalk between DNA methylation status and histone modification. Indeed, in the drm1 drm2 cmt3 mutant the overexpression of CLF gene, a component of PCR2 complex that performs trimethylation of histone H3 lysine 27, was accompanied by a high level of histone methylation, as evaluated through ChIP-qPCR analysis, and by a concomitant down-regulation of genes target of PRC2 complex action. Thus, the results obtained in these three years of PhD course are encouraging and may open new perspectives in the study of the DNA methylation in plants.
Impact of DNA methylation status on plant response to cd explored through a transcriptomic analysis
(2019-04-11) Pacenza, Marianna; Bitonti, Maria Beatrice; Cerra, Maria Carmela
Due to their sessile life style, plants are continuously exposed to a variety of abiotic and biotic stresses which could potentially hinder their growth, development, productivity and survival. In this scenario, it appears evident the relevance of epigenetic mechanisms in assuring growth plasticity to the plant and withstanding stresses through a rapid and extensive modification of gene expression in a manner that overcomes the restrictions of a highly stable DNA sequence. Epigenome landscape is largely related to DNA methylation process, which is one of the most significant players in the control of plant responses to environmental changes and stressors. On the other hand, all these responses are also under the control of an intricate signalling network which strongly involves the phytohormones, whose action is in turn influenced by epigenetic mechanisms. Despite this information, the complex mechanisms by which DNA methylation modulates plant stress responses are yet largely unresolved, mainly with respect to heavy metal stress, for which a metal- and speciesspecific response was evidenced. In order to gain further insight into these aspects, in the present work we performed a comparative transcriptomic analysis on the drm1 drm2 cmt3 (ddc) mutant of A. thaliana, defective in both maintenance and de novo DNA methylation, and WT plants exposed to a long lasting (21 days) Cd treatment at 25 and 50 μM concentrations. Attention was focused on Cd as one of the most toxic pollutants, widespread in both terrestrial and marine environment. The mutant was chosen as a suitable tool for investigating mechanisms and molecular processes that act in and are regulated by DNA methylation. Analyses of growth parameters and targeted cytophysiological features were also carried out. Concerning the results, transcriptomic analysis highlighted photosynthesis, stress responses and hormone biosynthesis as the genetic pathways more impacted by Cd treatment in both ddc mutant and WT. All these pathways are highly relevant for plant development. A more detailed analysis carried out on the pathways related to the phytohormones suggested that, under a prolonged heavy metal exposure, plant activity was directed to enhance and/or maintain the level and signalling of hormones which are relevant in sustaining the growth (auxins, cytokinins and gibberellins) more than those of hormones specifically related to stress response (jasmonic acid, abscisic acid and salicylic acid). This could represent the plant strategy to avoid the negative effects of long-lasting activity of stress-related hormones. Interestingly, such strategy could be more efficient in ddc mutant than in the WT. Indeed, likely due to a higher genome plasticity conferred to the mutant by its DNA hypomethylated status, in the ddc mutant the described transcriptomic differences have already been observed in the treatment with 25 μM Cd, while in the WT only in the treatment with 50 μM Cd. The outcome of this different modulation of gene expression was a better growth performance in ddc vs WT, as evidenced by growth parameters analysis. A tight relationship between the hormonerelated transcriptomic differences and the different cyto- morphophysiological features of ddc mutant vs WT under Cd treatment was also revealedUniversità della Calabria, Dipartimento di Biologia, Ecologia e Scienze della Terra. Dottorato di Ricerca in Scienze della Vita. Ciclo XXXI SSD BIO/01

Dipartimento di Biologia, Ecologia e Scienze della Terra - Tesi di dottorato

Browse

Filters

Settings

Sort By

Results per page

Search Results