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6th bioRxiv of 2017: Massive field data from rain manipulation

Posted on September 11, 2017

Field experiment with 517 A. thaliana accessions in Madrid & Tübingen read more

A rainfall-manipulation experiment with 517 Arabidopsis thaliana accessions

Exposito-Alonso et al. https://doi.org/10.1101/186767

The gold standard for studying natural selection is to quantify lifetime fitness in individuals from natural populations that have been grown together under different field conditions. This has been widely done in ecology to measure phenotypic selection in nature for a wide range of organisms -- an evolutionary force that seems to be most determined by local precipitation patterns. Studies that include whole-genome data would enable the translation of coefficients of selection to the genetic level, but such studies are still scarce, even though this type of genetic knowledge will be critical to predict the effect of climate change in natural populations. Here we present such an experiment including rainfall-manipulation with the plant Arabidopsis thaliana. The experiment was carried out in a Mediterranean and a Central European field station with rainout shelters to simulate a high and low rainfall treatment within each location. For each treatment combination, we planted 7 pots with one individual and 5 pots with 30 counted seeds of 517 whole-genome sequenced natural accessions covering the global species distribution. Survival, germination, flowering time, and final seed output were measured for ca. 25,000 pots, which contained ca. 14,500 individual plants and over 310,00 plants growing in small populations. This high-throughput phenotyping was only possible thanks to image analysis techniques using custom-made scripts. To make the data and processing code available, we created an R package dryAR (http://github.com/MoisesExpositoAlonso/dryAR).

In Nature Plants: Prominent TADs in rice

Posted on August 29, 2017

Different from Arabidopsis, the 3D genome of rice has clear TADs read more

Prominent topologically associated domains differentiate global chromatin packing in rice from Arabidopsis

Chang Liu, Ying-Juan Cheng, Jia-Wei Wang & Detlef Weigel

The non-random three-dimensional organization of genomes is critical for many cellular processes. Recently, analyses of genome-wide chromatin packing in the model dicot plant Arabidopsis thaliana have been reported. At a kilobase scale, the A. thaliana chromatin interaction network is highly correlated with a range of genomic and epigenomic features. Surprisingly, topologically associated domains (TADs), which appear to be a prevalent structural feature of genome packing in many animal species, are not prominent in the A. thaliana genome. Using a genome-wide chromatin conformation capture approach, Hi-C , we report high-resolution chromatin packing patterns of another model plant, rice. We unveil new structural features of chromatin organization at both chromosomal and local levels compared to A. thaliana, with thousands of distinct TADs that cover about a quarter of the rice genome. The rice TAD boundaries are associated with euchromatic epigenetic marks and active gene expression, and enriched with a sequence motif that can be recognized by plant-specific TCP proteins. In addition, we report chromosome decondensation in rice seedlings undergoing cold stress, despite local chromatin packing patterns remaining largely unchanged. The substantial variation found already in a comparison of two plant species suggests that chromatin organization in plants might be more diverse than in multicellular animals.

In Genome Biology: 3D genome of interspecific hybrids

Posted on August 28, 2017

Altered chromatin compaction & histone methylation in an interspecific Arabidopsis hybrid read more

Wangsheng Zhu et al., Genome Biology 2017 18:157, doi.org/10.1186/s13059-017-1281-4

Background: The merging of two diverged genomes can result in hybrid offspring that phenotypically differ greatly from both parents. In plants, interspecific hybridization plays important roles in evolution and speciation. In addition, many agricultural and horticultural species are derived from interspecific hybridization. However, the detailed mechanisms responsible for non-additive phenotypic novelty in hybrids remain elusive.

Results: In an interspecific hybrid between Arabidopsis thaliana and A. lyrata, the vast majority of genes that become upregulated or downregulated relative to the parents originate from A. thaliana. Among all differentially expressed A. thaliana genes, the majority is downregulated in the hybrid. To understand why parental origin affects gene expression in this system, we compare chromatin packing patterns and epigenomic landscapes in the hybrid and parents. We find that the chromatin of A. thaliana, but not that of A. lyrata, becomes more compact in the hybrid. Parental patterns of DNA methylation and H3K27me3 deposition are mostly unaltered in the hybrid, with the exception of higher CHH DNA methylation in transposon-rich regions. However, A. thaliana genes enriched for the H3K27me3 mark are particularly likely to differ in expression between the hybrid and parent.

Conclusions: It has long been suspected that genome-scale properties cause the differential responses of genes from one or the other parent to hybridization. Our work links global chromatin compactness and H3K27me3 histone modification to global differences in gene expression in an interspecific Arabidopsis hybrid.

2017 Campus Soccer Tournament

Posted on August 11, 2017

Two awesome WeigelWorld soccer teams participated in this year’s campus tournament. read more

Denisovans

The Elephants

 

 

In Science: Ancient maize adaptation to temperate climate

Posted on August 04, 2017

Genomic estimation reveals when ancient maize became adapted to temperate climate read more

Genomic estimation of complex traits reveals ancient maize adaptation to temperate North America

Swarts, K., Gutaker, R. M., Benz, B., Blake, M., Bukowski, R., Holland, J., Kruse-Peeples, M., Lepak, N., Prim, L., Romay, M. C., Ross-Ibarra, J., Sanchez-Gonzalez, J. d. J., Schmidt, C., Schuenemann, V. J., Krause, J., Matson, R. G., Weigel, D., Buckler, E. S., Burbano, H. A. (2017)

People introduced maize to the southwestern US by 4,000 years ago; full agriculture was established quickly in the lowland deserts but delayed in the temperate uplands for 2,000 years. We test if the earliest upland maize was adapted for early flowering, a characteristic of modern temperate maize. We sequenced fifteen 1,900-year old maize cobs from Turkey Pen Shelter in the temperate Southwest. Indirectly validated genomic models predicted that Turkey Pen maize was marginally adapted with respect to flowering, as well as short, tillering and segregating for yellow kernel color. Temperate adaptation drove modern population differentiation and was selected in situ from ancient standing variation. Validated prediction of polygenic traits improves our understanding of ancient phenotypes and the dynamics of environmental adaption.

 

Collaboration with Huq lab: Splicing and phytochrome signaling

Posted on July 31, 2017

Out in PNAS: SPF45-related splicing factor, phytochrome signaling & pre-mRNA splicing read more

Xin et al. (2017) SPF45-related splicing factor for phytochrome signaling promotes photomorphogenesis by regulating pre-mRNA splicing in Arabidopsis. Proc Natl Acad Sci USA, doi: 10.1073/pnas.1706379114

Pre-mRNA processing not only enhances the diversity encoded in the genome without the need to increase the number of genes but also provides a means to adjust cellular transcript abundance. Environmental light has a profound effect on transcript accumulation, but how this is partitioned between transcriptional and posttranscriptional processes is largely unknown. Here we describe the identification and characterization of the splicing factor for phytochrome signaling (SFPS), which directly interacts with the photoreceptor phytochrome B. sfps seedlings are hyposensitive to light and display pre-mRNA splicing defects in a large number of genes, many of which regulate light signaling and the circadian clock. Thus, light might control pre-mRNA splicing in addition to transcription of many genes through SFPS to promote photomorphogenesis.

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Upcoming Events

Oct
04

MiKo Talk Dek Woolfson

October 4, 3 pm
MPH Lecture Hall

Title: "TBA"


Oct
09

Giovanna’s thesis defense

October 9, 10 am
Room N11, Auf der Morgenstelle 3, Tübingen University

Giovanna will defend her PhD thesis entitled 'Exploring the role of temperature regulated alternative splicing in flowering time and morphogenesis'


Oct
10

Weill Institute Symposium

October 10, 2017
at Cornell University

Detlef speaking at Weill Institute Symposium: "Genetics and epigenetics of adaptation to the environment"