How DNA Changes Shaped the Evolution and Domestication of Lettuce

Jenn Hoskins
18th June, 2024

How DNA Changes Shaped the Evolution and Domestication of Lettuce

Image Source: Natural Science News, 2024

Key Findings

  • The study by the National University of Singapore focused on the role of epigenetic variation in lettuce domestication and divergence
  • Researchers found significant differences in DNA methylation patterns between wild and domesticated lettuce
  • Specific genes showed differential methylation between leafy and stem lettuce, influencing plant development and stress response
Lettuce (Lactuca sativa L.) is a staple vegetable crop globally, with a significant economic impact. It is believed to have been domesticated from a single wild ancestor, Lactuca serriola, and subsequently diverged into two main types: leafy lettuce and stem lettuce. However, the role of epigenetic variation in this domestication and divergence has remained largely unexplored. A recent study conducted by the National University of Singapore aims to shed light on this aspect[1]. Epigenetic variation refers to changes in gene expression that do not involve alterations to the underlying DNA sequence. These changes can be influenced by environmental factors and can be heritable. Understanding how epigenetic variation contributes to the domestication and divergence of lettuce could provide valuable insights for crop breeding and improvement. Previous studies have laid the groundwork for understanding lettuce domestication and genetic variation. One study sequenced 240 lettuce accessions and identified 1.1 million single-nucleotide polymorphisms (SNPs). This study revealed that lettuce underwent a single domestication event and identified regions of the genome that were subject to selective sweeps during domestication and divergence[2]. Another study sequenced 445 Lactuca accessions and mapped genome variations, revealing that lettuce was first domesticated near the Caucasus, marked by the loss of seed shattering[3]. Additionally, a study using genotyping-by-sequencing (GBS) on 441 lettuce accessions highlighted substantial genetic divergence among different horticultural types and identified regions associated with delayed bolting[4]. The recent study by the National University of Singapore builds on these findings by focusing on the role of epigenetic variation. The researchers aimed to determine how epigenetic changes have influenced the domestication and divergence of lettuce. To achieve this, they analyzed DNA methylation patterns—one of the most common types of epigenetic modifications—in various lettuce accessions. DNA methylation involves the addition of a methyl group to the DNA molecule, typically at cytosine bases. This modification can affect gene expression by turning genes on or off. By comparing DNA methylation patterns between wild and domesticated lettuce, as well as between different types of domesticated lettuce, the researchers sought to identify epigenetic changes associated with domestication and divergence. The study found significant differences in DNA methylation patterns between wild and domesticated lettuce. These differences were particularly pronounced in regions of the genome previously identified as selective sweeps during domestication[2]. This suggests that epigenetic changes in these regions may have played a role in the domestication process. Moreover, the study identified specific genes that showed differential methylation between leafy and stem lettuce. These genes are involved in various biological processes, including plant development and stress response. The findings indicate that epigenetic variation has contributed to the morphological divergence of lettuce into its two major types. The researchers also explored the potential for using epigenetic markers in lettuce breeding. They identified several epigenetic loci that could be targeted to develop new lettuce varieties with desirable traits, such as improved nutritional value and stress tolerance. This approach could complement traditional breeding methods and help overcome some of the limitations associated with genetic variation alone. In summary, the study conducted by the National University of Singapore provides new insights into the role of epigenetic variation in lettuce domestication and divergence. By analyzing DNA methylation patterns, the researchers identified epigenetic changes associated with domestication and morphological divergence. These findings build on previous studies that have mapped genetic variations and selective sweeps in lettuce[2][3][4], offering a more comprehensive understanding of how both genetic and epigenetic factors have shaped the evolution of this important crop. The study's implications for lettuce breeding could lead to the development of new varieties with enhanced traits, benefiting both growers and consumers.

AgricultureGeneticsPlant Science

References

Main Study

1) DNA methylation variations underlie lettuce domestication and divergence

Published 17th June, 2024

https://doi.org/10.1186/s13059-024-03310-x

Related Studies

2) RNA sequencing provides insights into the evolution of lettuce and the regulation of flavonoid biosynthesis.

https://doi.org/10.1038/s41467-017-02445-9

3) Whole-genome resequencing of 445 Lactuca accessions reveals the domestication history of cultivated lettuce.

https://doi.org/10.1038/s41588-021-00831-0

4) Population genetics and genome-wide association studies provide insights into the influence of selective breeding on genetic variation in lettuce.

https://doi.org/10.1002/tpg2.20086


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