Project description:Polyploidization and introgression are major events driving plant genome evolution and influencing crop breeding. However, the mechanisms underlying the higher-order chromatin organization of subgenomes and alien chromosomes are largely unknown. We probe the three-dimensional chromatin architecture of Aikang 58 (AK58), a widely-cultivated allohexaploid wheat variety carrying the 1RS/1BL translocation chromosome. The regions involved in inter-chromosomal interactions, both within and between subgenomes, have highly similar sequences. Subgenome-specific territories tend to be connected by subgenome-dominant homologous transposable elements (TEs). The alien 1RS chromosomal arm, which was introgressed from rye and differs from its wheat counterpart, has relatively few inter-chromosome interactions with wheat chromosomes. An analysis of local chromatin structures reveals topologically associating domain (TAD)-like regions covering 52% of the AK58 genome, the boundaries of which are enriched with active genes, zinc-finger factor-binding motifs, CHH methylation, and 24-nt small RNAs. The chromatin loops are mostly localized around TAD boundaries, and the number of gene loops is positively associated with gene activity. The present study reveals the impact of the genetic sequence context on the higher-order chromatin structure and subgenome stability in hexaploid wheat. Specifically, we characterized the sequence homology-mediated inter-chromosome interactions and the non-canonical role of subgenome-biased TEs. Our findings may have profound implications for future investigations of the interplay between genetic sequences and higher-order structures and their consequences on polyploid genome evolution and introgression-based breeding of crop plants.
Project description:The phytochromes (PHYs) are a family of photoreceptors which absorb light of red and far-red wavelengths to modulate developmental responses in photosynthetic organisms. We developed knockout mutants of PHYB and PHYC in wheat and performed replicated RNA-seq studies to analyze and compare the regulons of each phytochrome under long day photoperiods. Illumina Truseq v2 RNA-seq libraries were constructed from four biological replicates of phyBnull mutants and their wild-type sister lines and of phyCnull mutants and their wild-type sister lines. Subsequently, the entire experiment was replicated. Reads were mapped to the draft assembly (v2.2) of the wheat genome provided by the International Wheat Genome Sequencing Consortium (IWGSC) and transcribed regions were identifed by mapping a non-redundant set of transcripts to this genomic assembly. Sequencing reads mapping uniquely within these identified transcribed regions were used to determine relative expression profiles. Loci which were differentially expressed in both experimental replicates were designated high-confidence PHYB-regulated and PHYC-regulated genes, respectively. A GTF file is provided detailing the location of the 150,754 loci within the IWGSC pseduomolecules and contig scaffold followed by the longest transcribed sequence mapping to this region. Most, but not all, transcribed sequences are annotated through Ensembl.
Project description:Introgression of a high molecular weight glutenin subunit (HMW-GS) gene, 1Ay21*, into commercial wheat cultivars increased overall grain protein content and bread-making quality by unknown mechanisms. As well as increased abundance of 1Ay HMW-GS, 115 differentially expressed proteins (DEPs) were discovered between three cultivars and corresponding introgressed near-isogenic lines (NILs). Functional category analysis showed that the DEPs were predominantly other storage proteins, and proteins involved in protein synthesis, protein folding, protein degradation, stress response and grain development. Nearly half the genes encoding the DEPs showed strong co-expression patterns during grain development. Promoters of these genes are enriched in elements associated with transcription initiation and light response, indicating a potential connection between these cis-elements and grain protein accumulation. A model of how this HMW-GS enhances the abundance of machinery for protein synthesis and maturation during grain filling is proposed. This analysis not only provides insights into how introgression of the 1Ay21* improves grain protein content, but also directs selection of protein candidates for future wheat quality breeding programmes.
Project description:The Italian island of Sardinia is well known in studies of human population isolates. It is also home to the Fonni's Dog, a breed of canine whose development was reliant on the functionality of the dog. Using genome-wide variant and sequence analyses, we have characterized the Fonni's Dog relative to 27 other dog breeds from the Mediterranean region. We determine introgression events relevant to Mediterranean breed development and describe how the Fonni's dog presents an intriguing model demonstrating the characteristics of traditional human population isolates and, in particular, exhibiting the unique demographic composition of the people of Sardinia.