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30. June 2025
Martin Lysák from CEITEC Masaryk University (MUNI), together with colleagues from Huazhong Agricultural University in China, coordinated the sequencing of the largest ever reported genome in the Brassicaceae family, which includes the model plant Arabidopsis thaliana as well as rapeseed and broccoli. The genome belongs to Matthiola incana, commonly known as stock, a fragrant ornamental species that is grown both as a cut flower and as a bedding plant. The genome of Matthiola (2 gigabase pairs) is twelve times larger than that of Arabidopsis, even though both species have a similar number of chromosomes.
This unusually large genome is consistss of more than 70% retrotransposons – autonomous DNA sequences capable of copying and inserting themselves into different parts of the genome. These non-coding sequences have caused a significant expansion of the Matthiola genome to twelve times the size of the Arabidopsis genome, mostly in the last two million years. The exact reason why such a massive expansion has occurred in Matthiola and its close relatives remains unclear, but it may be linked to the genome’s inability to regulate retrotransposon proliferation or to the plant’s tolerance to their accumulation.
“The Matthiola genome allows us to study how the genome structure in the model plant family can change over time, without the influence of polyploidy and diploidization,” explains Martin Lysák, research group leader at CEITEC Masaryk University and one of the lead authors of the study. Polyploidy, the duplication of the entire genomes and chromosome sets, is common in plants. The team also found that Matthiola chromosomes have a markedly different pattern of epigenetic marks than other Brassicaceae species with small or smaller genomes. The researchers focused on DNA methylation, which was found to be extensive and evenly distributed along the chromosomes of Matthiola. It is hypothesized that this epigenetic silencing helps to suppress the activity of the numerous potentially harmful retrotransposons.
Matthiola is well known for its wide range of flower colours, ranging from white to deep reds. The genome sequence allowed the identification of genes and transcription factors involved in the biosynthesis of pelargonidin, a pigment responsible for the colour diversity of Matthiola flowers. Understanding this biosynthetic pathway could support targeted genome editing to develop new varieties with different flower colours.
“The unique genome of Matthiola shows us how plant genomes can massively expand through the accumulation of non-coding sequences. It helps us to understand how such expansions affect chromosome architecture, gene activity and the extent to which ‘genome obesity’ influences a plant’s adaptation to its environment. Reading the genetic information of such an 'obese' genome enables comparative studies with small genomes and helps us gain insights into the mechanisms underlying genome size and structural variation,” adds Lysák.
The article was published in the prestigious journal Plant Biotechnology Journal.
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