We also celebrated the three freshly minted PhD graduates, Diep Tran (starting as a postdoc with Lionel Navarro at the ENS in Paris), Jorge Kageyama (starting as a postdoc with Barbara Treutlein at the MPI-EVA in Leipzig) and Cris Zaidem (starting in 2017 as a postdoc with Michael Purugganan at NYU)
Polina Yu Novikova, Nora Hohmann, Viktoria Nizhynska, Takashi Tsuchimatsu, Jamshaid Ali, Graham Muir, Alessia Guggisberg, Tim Paape, Karl Schmid, Olga M Fedorenko, Svante Holm, Torbjörn Säll, Christian Schlötterer, Karol Marhold, Alex Widmer, Jun Sese, Kentaro K Shimizu, Detlef Weigel, Ute Krämer, Marcus A Koch & Magnus Nordborg
The notion of species as reproductively isolated units related through a bifurcating tree implies that gene trees should generally agree with the species tree and that sister taxa should not share polymorphisms unless they diverged recently and should be equally closely related to outgroups. It is now possible to evaluate this model systematically. We sequenced multiple individuals from 27 described taxa representing the entire Arabidopsis genus. Cluster analysis identified seven groups, corresponding to described species that capture the structure of the genus. However, at the level of gene trees, only the separation of Arabidopsis thaliana from the remaining species was universally supported, and, overall, the amount of shared polymorphism demonstrated that reproductive isolation was considerably more recent than the estimated divergence times. We uncovered multiple cases of past gene flow that contradict a bifurcating species tree. Finally, we showed that the pattern of divergence differs between gene ontologies, suggesting a role for selection.
The three-dimensional packing of the genome plays an important role in regulating gene expression. We have used Hi-C, a genome-wide chromatin conformation capture (3C) method, to analyze Arabidopsis thaliana chromosomes dissected into subkilobase segments, which is required for gene-level resolution in this species with a gene-dense genome. We found that the repressive H3K27me3 histone mark is overrepresented in the promoter regions of genes that are in conformational linkage over long distances. In line with the globally dispersed distribution of RNA polymerase II in A. thaliana nuclear space, actively transcribed genes do not show a strong tendency to associate with each other. In general, there are often contacts between 5' and 3' ends of genes, forming local chromatin loops. Such self-loop structures of genes are more likely to occur in more highly expressed genes, although they can also be found in silent genes. Silent genes with local chromatin loops are highly enriched for the histone variant H3.3 at their 5' and 3' ends but depleted of repressive marks such as heterochromatic histone modifications and DNA methylation in flanking regions. Our results suggest that, different from animals, a major theme of genome folding in A. thaliana is the formation of structural units that correspond to gene bodies.
August 28-31, 2016
Detlef will give an overview of the plant-microbe and immunity related work of the group at the "Wild Plant Pathosystems" meeting in Helsinki
in Marburg, Germany
Moisés speaking about "Adaptation Genomics to Drought"
September 14, 11 am
MPH Lecture Hall