Salt Stress Induced Variation in DNA Methylation Pattern and Its Influence on Gene Expression in Contrasting Rice Genotypes

BACKGROUND: Salinity is a major environmental factor limiting productivity of crop plants including rice in which wide range of natural variability exists. Although recent evidences implicate epigenetic mechanisms for modulating the gene expression in plants under environmental stresses, epigenetic changes and their functional consequences under salinity stress in rice are underexplored. DNA methylation is one of the epigenetic mechanisms regulating gene expression in plant's responses to environmental stresses. Better understanding of epigenetic regulation of plant growth and response to environmental stresses may create novel heritable variation for crop improvement. METHODOLOGY/PRINCIPAL FINDINGS: Methylation sensitive amplification polymorphism (MSAP) technique was used to assess the effect of salt stress on extent and patterns of DNA methylation in four genotypes of rice differing in the degree of salinity tolerance. Overall, the amount of DNA methylation was more in shoot compared to root and the contribution of fully methylated loci was always more than hemi-methylated loci. Sequencing of ten randomly selected MSAP fragments indicated gene-body specific DNA methylation of retrotransposons, stress responsive genes, and chromatin modification genes, distributed on different rice chromosomes. Bisulphite sequencing and quantitative RT-PCR analysis of selected MSAP loci showed that cytosine methylation changes under salinity as well as gene expression varied with genotypes and tissue types irrespective of the level of salinity tolerance of rice genotypes. CONCLUSIONS/SIGNIFICANCE: The gene body methylation may have an important role in regulating gene expression in organ and genotype specific manner under salinity stress. Association between salt tolerance and methylation changes observed in some cases suggested that many methylation changes are not "directed". The natural genetic variation for salt tolerance observed in rice germplasm may be independent of the extent and pattern of DNA methylation which may have been induced by abiotic stress followed by accumulation through the natural selection process

The role of networks to overcome large-scale challenges in tomography : the non-clinical tomography users research network

Our ability to visualize and quantify the internal structures of objects via computed tomography (CT) has fundamentally transformed science. As tomographic tools have become more broadly accessible, researchers across diverse disciplines have embraced the ability to investigate the 3D structure-function relationships of an enormous array of items. Whether studying organismal biology, animal models for human health, iterative manufacturing techniques, experimental medical devices, engineering structures, geological and planetary samples, prehistoric artifacts, or fossilized organisms, computed tomography has led to extensive methodological and basic sciences advances and is now a core element in science, technology, engineering, and mathematics (STEM) research and outreach toolkits. Tomorrow's scientific progress is built upon today's innovations. In our data-rich world, this requires access not only to publications but also to supporting data. Reliance on proprietary technologies, combined with the varied objectives of diverse research groups, has resulted in a fragmented tomography-imaging landscape, one that is functional at the individual lab level yet lacks the standardization needed to support efficient and equitable exchange and reuse of data. Developing standards and pipelines for the creation of new and future data, which can also be applied to existing datasets is a challenge that becomes increasingly difficult as the amount and diversity of legacy data grows. Global networks of CT users have proved an effective approach to addressing this kind of multifaceted challenge across a range of fields. Here we describe ongoing efforts to address barriers to recently proposed FAIR (Findability, Accessibility, Interoperability, Reuse) and open science principles by assembling interested parties from research and education communities, industry, publishers, and data repositories to approach these issues jointly in a focused, efficient, and practical way. By outlining the benefits of networks, generally, and drawing on examples from efforts by the Non-Clinical Tomography Users Research Network (NoCTURN), specifically, we illustrate how standardization of data and metadata for reuse can foster interdisciplinary collaborations and create new opportunities for future-looking, large-scale data initiatives

BLAST results of ten randomly selected polymorphic methylated fragments and their location on rice genome.

<p>BLAST results of ten randomly selected polymorphic methylated fragments and their location on rice genome.</p

A representative MSAP gel using the primer combination <i>Eco</i>RI-ACG/<i>Msp</i>I-AATC.

<p>Both control and salinity stressed root and shoot of rice genotypes, IR29, Nipponbare (Nipp), Pokkali (Pokk), Geumgangbyeo (Geum) were used for MSAP analysis. EH and EM refer to digestion with <i>Eco</i>RI+<i>Hpa</i>II and <i>Eco</i>RI+<i>Msp</i>I, respectively. RC: root control; RS: root stress; SC: shoot control; SS: shoot stress.</p

Analysis of DNA methylation patterns under salinity stress with respect to control condition in the shoot and root of seedlings of rice varieties, IR29, Nipponbare (Nipp), Pokkali (Pokk), and Geumgangbyeo (Geum).

<p>A score of 1 and 0 represents presence and absence of bands, respectively. Values in parentheses indicate percentage of bands in each pattern which was determined by dividing number of bands in each pattern by total number of bands in all three patterns.</p

DNA methylation changes in shoot and root at seedling stage under non-stress and salinity stress conditions.

a<p>MSAP (%)  =  [(II+III+IV)/(I+II+III+IV)]×100;</p>b<p>Fully methylated bands (%) = [(III+IV)/(I+II+III+IV)]×100;</p>c<p>Hemimethylated bands (%) = [(II)/(I+II+III+IV)]×100.</p><p>Type I indicated absence of methylation due to the presence of bands in both <i>EcoR</i>I/<i>Hpa</i>II and <i>Eco</i>RI/<i>Msp</i>I digest; type II bands appeared only in <i>EcoR</i>I/<i>Hpa</i>II digestion but not in the <i>Eco</i>RI/<i>Msp</i>I digest; type III generated bands obtained in <i>Eco</i>RI/<i>Msp</i>I digest but not in the <i>EcoR</i>I/<i>Hpa</i>II digest; and type IV represents the absence of band in both enzyme combinations.</p

Precocious chondrocyte differentiation disrupts skeletal growth in Kabuki syndrome mice.

To access publisher's full text version of this article click on the hyperlink belowKabuki syndrome 1 (KS1) is a Mendelian disorder of the epigenetic machinery caused by mutations in the gene encoding KMT2D, which methylates lysine 4 on histone H3 (H3K4). KS1 is characterized by intellectual disability, postnatal growth retardation, and distinct craniofacial dysmorphisms. A mouse model (Kmt2d+/βGeo) exhibits features of the human disorder and has provided insight into other phenotypes; however, the mechanistic basis of skeletal abnormalities and growth retardation remains elusive. Using high-resolution micro-CT, we show that Kmt2d+/βGeo mice have shortened long bones and ventral bowing of skulls. In vivo expansion of growth plates within skulls and long bones suggests disrupted endochondral ossification as a common disease mechanism. Stable chondrocyte cell lines harboring inactivating mutations in Kmt2d exhibit precocious differentiation, further supporting this mechanism. A known inducer of chondrogenesis, SOX9, and its targets show markedly increased expression in Kmt2d-/- chondrocytes. By transcriptome profiling, we identify Shox2 as a putative KMT2D target. We propose that decreased KMT2D-mediated H3K4me3 at Shox2 releases Sox9 inhibition and thereby leads to enhanced chondrogenesis, providing a potentially novel and plausible explanation for precocious chondrocyte differentiation. Our findings provide insight into the pathogenesis of growth retardation in KS1 and suggest therapeutic approaches for this and related disorders.Wellcome Trust Baltimore Center for Musculoskeletal Science 2015 Pilot and Feasibility Award William and Ella Owens Medical Research Foundation Johns Hopkins School of Medicine Clinician Scientist Award Hartwell Foundation Individual Biomedical Research Award United States Department of Health & Human Services National Institutes of Health (NIH) - USA Louma G. Foundatio