How Tomato DNA Structures Are Shaped by KRYPTONITE Protein

Jenn Hoskins
6th July, 2024

How Tomato DNA Structures Are Shaped by KRYPTONITE Protein

A comprehensive epigenetic atlas for Tomato (Solanum lycopersicum) defines 16 distinct chromatin states based on the unique nuclear localization (a), genomic distribution (b, c), and transcriptional correlation (d, e) of 26 histone marks, establishing the opposing euchromatic and heterochromatic landscapes (f) that are fundamental to the genome's 3D organization.

Image adapted from: An et al. / CC BY (Source)

Key Findings

  • Researchers at Université Paris-Saclay studied the 3D genome architecture of the tomato, focusing on histone modifications and RNA polymerase II distribution
  • The study found that the abnormal deposition of the histone modification H3K9ac reorganizes chromatin structure, defining TAD-like borders in the tomato genome
  • These findings highlight the role of H3K9ac in shaping the 3D genome structure and suggest that different histone modifications can distinctly influence genome topology in plants
The three-dimensional (3D) organization of genomes is a crucial aspect of gene regulation and cellular function, influencing how genes are expressed and silenced. While this concept has been extensively studied in animals, plants exhibit a more diverse genomic conformation across species. A recent study conducted by researchers at Université Paris-Saclay[1] has provided significant insights into the 3D genome architecture of the tomato (Solanum lycopersicum), an agriculturally important crop. This study explored the epigenetic landscape of tomato, focusing on 26 histone modifications and RNA polymerase II distribution, revealing the intricate interplay between chromatin states and genome topology. Histones are proteins around which DNA winds, forming a structure known as chromatin. Modifications to histones, such as the addition of acetyl or methyl groups, can influence whether a gene is active or silenced. The study by Université Paris-Saclay specifically investigated the role of the histone modification H3K9ac (acetylation of lysine 9 on histone H3) in shaping the 3D structure of the tomato genome. The researchers found that the ectopic (abnormal) deposition of H3K9ac triggered a reorganization of the chromatin structure, defining different TAD-like borders. Topologically associating domains (TADs) are regions of the genome that interact more frequently with themselves than with other regions, creating distinct 3D structures within the nucleus. These TADs play a significant role in regulating gene expression by segregating active and inactive chromatin regions. In animals, TAD borders are typically enriched with active genes and clusters of architectural proteins[2]. The tomato study revealed that similar TAD-like structures exist in plants and that H3K9ac is crucial in defining these borders. The findings from this study are consistent with previous research on the role of histone modifications in genome organization. For instance, it has been shown that H3K9me2 (dimethylation of lysine 9 on histone H3) contributes to the formation of inactive chromatin compartments in mammalian cells[3]. The tomato study expands on this by demonstrating that H3K9ac, a mark associated with active chromatin, can influence the 3D genome structure in plants, suggesting that different histone modifications can have distinct roles in shaping genome topology. Additionally, the study's results align with earlier findings on the plasticity of TAD organization. In Drosophila, temperature stress was found to induce relocalization of architectural proteins from TAD borders to inside TADs, leading to a reorganization of the 3D nuclear structure[2]. This plasticity highlights the dynamic nature of genome organization, which can be influenced by various factors, including histone modifications. The investigation into the tomato genome also revealed a rich and nuanced epigenetic landscape, with distinct chromatin states associated with heterochromatin (tightly packed, inactive chromatin) formation and gene silencing. This is particularly relevant given the role of interspecific hybridization in plant evolution and speciation. Previous research on Arabidopsis hybrids demonstrated that the merging of diverged genomes could result in hybrid offspring with novel phenotypes, partly due to changes in chromatin compactness and histone modifications[4]. The tomato study adds to this understanding by showing how specific histone modifications can influence genome topology and gene expression in a crop species. In summary, the study conducted by Université Paris-Saclay underscores the critical role of H3K9ac in shaping the 3D genome structure of tomato. By revealing the complex interplay between chromatin states and genome topology, this research provides valuable insights into the epigenetic regulation of gene expression in plants. These findings not only enhance our understanding of plant genome organization but also have potential implications for crop improvement and agricultural practices.

GeneticsBiochemPlant Science

References

Main Study

1) An atlas of the tomato epigenome reveals that KRYPTONITE shapes TAD-like boundaries through the control of H3K9ac distribution.

Published 9th July, 2024 (future Journal edition)

https://doi.org/10.1073/pnas.2400737121

Related Studies

2) Widespread rearrangement of 3D chromatin organization underlies polycomb-mediated stress-induced silencing.

https://doi.org/10.1016/j.molcel.2015.02.023

3) Regulation of mammalian 3D genome organization and histone H3K9 dimethylation by H3K9 methyltransferases.

https://doi.org/10.1038/s42003-021-02089-y

4) Altered chromatin compaction and histone methylation drive non-additive gene expression in an interspecific Arabidopsis hybrid.

https://doi.org/10.1186/s13059-017-1281-4


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