Five days on the Spanish coast discussing one of our favorite topics (epigenetics) sounds like a great time to us. Unfortunately, a European trip didn’t work out, so count us jealous that Manu Dubin from the Gregor Mendel Institute volunteered to take on the very “tough” assignment of covering the ESF-EMBO Symposium – Epigenetics in Context on EpiGenie’s behalf. Take a look at Manu’s report to see what we all missed:
The ESF-EMBO Symposium – Epigenetics in Context: From Ecology to Evolution took place from September 18th to 23rd, 2011 at the Hotel Eden Rock resort on the Mediterranean coast at Sant Feliu de Guixols, Spain. The organisers Vincent Colot (France) and Oliver Bossdorf (Switzerland) had selected a diverse range of speakers from fields ranging from ecology and epigenetics to population genetics and mathematics. Likewise the model systems presented were also highly varied, in addition to the usual suspects, we heard exciting talks on epigenetics of nectar yeast that live in flowers, dandelions, tropical paper wasps, Norway spruce, oysters, orchids, Trinidadian guppies, sea-bass, salt-marsh cordgrass and trematodes.
Topics covered included epigenetic mechanisms, environmental responses, transgenerational effects, mapping genome x epigenome x phenotype interactions, theoretical approaches and evolutionary epigenetics. In addition to this the organisers managed to fit in numerous poster sessions while the three-hour lunch breaks allowed the diverse field of participants to exchange ideas and knowledge as they relaxed on the beach or by the pool.
Epigenetic memory in the germ line of C. elegans
Bill Kelly, Emory University
Gene expression patterns established in the adult germ line of C. elegans can be heritably transmitted to the following generations. Although DNA methylation is generally considered to be the most likely mechanism for transgenerational inherence C. elegans lacks this mark and instead transmission of differential expression patterns between generations occurs via methylation of histone H3 at lysines 4 and 36. In the germ line these marks are retained on genes that have previously been transcribed even in the absence of transcription and are not removed during germ line reprogramming. This memory requires the activity of a primordial germ cell expressed maintenance histone methyltransferase that is able to maintain the H3K36 methylation on genes for more than twenty generations even in the absence of transcription.
Epigenetic events underlying phenotypic plasticity in Polistes wasps.
Solenn Patalando, Brabraham Instiute
Dr. Patalando introduced Polistes wasps as a model for understanding epigenetic events underlying phenotypic plasticity in insects. Caste determination occurs in many social insects and at least in some cases appears to be controlled by epigenetic processes. Unlike bees were caste differentiation occurs at the egg stage, Polistes caste is specified in adulthood and can be experimentally manipulated by removing the existing queen from a colony. This leads to conflict between members of the worker caste, with the dominant one differentiating to become the new queen.
Younger workers are more likely to become the new queen, possibly because they retain greater plasticity. The queen and worker castes differ in their transcriptome profiles and also have different dynamics of DNA methylation levels in the brain.
Transgenerational consequences of stress exposure in dandelions
Koen Verhoven, Netherlands Institute of Ecology
Although diploid and tetraploid dandelion populations exist, in most parts of the world this species is triploid and reproduces asexually via apomixis. These clonal populations provide a great tool to study epigenetic variation in the absence of genetic variation in both the lab and in nature.
Artificial triploids were created by crossing diploid mother and a polyploid father and probed with methylation sensitive-AFLP markers. Differences in methylation patterns with respect to both parental strains were detected and transmitted to the progeny with non-mendalian segregation ratios. Populations grown under stress conditions had more variation in DNA methylation, most of which was stably inherited by subsequent generations.
In some cases progeny of stressed plants displayed improved fitness compared to those from non-stressed plants, however these effects were small and difficult to reproduce, underscoring the difficulty in producing robust transgenerational effects in experimental settings.
Spontaneous epigenetic variation in the Arabidopsis methylome
Claude Becker, Max Plank Institute
Whole genome bisulphite sequencing of 10 Arabidopsis lines, which had been propagated for 30 generations by single seed decent, was used to identify differentially methylated regions. Although many individual differentially methylated cytosines were detected, larger differentially methylated regions were relatively rare and in only a few cases were directly associated with changes in gene expression. In general the these epialleles seemed to occur in quite a random manner and were frequently reversible suggesting that for natural selection to act effectively on them the selection will have to be quite strong.
Population Epigenomics: Characterization of epialleles in Arabidopsis
Robert J. Schmitz, The Salk Institute
Dr Schmitz presented bisulphite sequencing results very similar to Claude Becker from a partially overlapping set of Arabidopsis lines that had been propagated for 30 generations. In addition, Robert examined differences in the methylome of close to 200 hundred accessions (genetically diverse inbred lines collected from all over the world). He found widespread differences in epialleles between the accessions and by association mapping of methylQTLs he found that many of them had an underlying genetic basis, most of which was in cis.
Small RNAs mediate transposon instability
Miloš Tanurdžic, Cold Spring Harbor
When an inter-specific hybrid is created by crossing Arabidopsis thaliana with Arabidopsis arenosa the immediate decedents displayed a wide range of phenotypes and widespread loss of silencing. In particular transposable elements (TE) present in the paternal (pollen), but not maternal (seed) genome were highly expressed in the F1 generation. These TE’s were present as extrachromosomal copies and extensive 21nt easiRNA’s (epigenetically activated siRNA’s) against them could be detected in leaves. In later generations copies of these TE’s become silenced as they accumulate DNA methylation and associated 24 nt siRNA’s. This phenomenon appears to be due to mismatch between incoming paternal TE’s and the cache of maternal siRNAs, which allows the recognition of “self” and “non-self” TE’s.
Epigenetic control of pollination syndromes
Ueli Grossniklaus, University of Zurich
Dr. Grossniklaus reported that what were thought to be two separate Mimulus taxa, a red bird-pollinated species and a yellow insect-pollinated species are in fact epigenetic variants of the same species. He showed that a plant can convert from the yellow to the red morph over a number of years and that this process is occurring in the wild, presumably due to environmental changes. Although flower colour is heritable, it reverts at low frequency. The trait segregates in a non-mendelian fashion as the one epiallele can paramutate the other in trans.
**EpiGenie would like to pass along many thanks to Dr Manu Dubin, who is a Postdoctoral Fellow in the Mittelsten Scheid Group at the Gregor Mendel Institute, for providing coverage of this event.