2025-12-15 マックス・プランク研究所
Variation in Cardamine hirsuta leaf form created by CRISPR/Cas9 mutations at the LMI/RCO locus.
<関連情報>
- https://www.mpg.de/25881196/diversity-through-repression
- https://www.pnas.org/doi/10.1073/pnas.2515732122
エンハンサー内の抑制配列の進化はアブラナ科植物の形態的多様性に貢献した Evolution of repressive sequences within an enhancer contributed to morphological diversity in crucifer plants
Alessandro Popoli, Remco A. Mentink, Lisa Brombach, +7 , and Miltos Tsiantis
Proceedings of the National Academy of Sciences Published:December 16, 2025
DOI:https://doi.org/10.1073/pnas.2515732122
Significance
Enhancers are regulatory DNA sequences that control gene expression and drive morphological evolution. Yet, how they diversify to create new expression domains remains unclear. We explore this by investigating an enhancer of the RCO plant homeobox gene, which arose through gene duplication and promotes leaf complexity. Compared to its ancestral counterpart, the RCO enhancer is less stringently required for RCO expression and is subject to more repression. This repression helped establish RCO’s expression pattern while avoiding potentially pleiotropic effects arising from its change in expression. Our work highlights regulatory features of a diversity-linked enhancer and underscores the importance of repressive sequences in morphological evolution.
Abstract
Cis-regulatory sequences, such as enhancers, play a crucial role in morphological evolution, but how their diversification leads to evolution of novel expression patterns that underpin diversity is still poorly understood. Recent work suggests that the function of enhancers is influenced by their genomic sequence context more than previously thought, further complicating our understanding of their contribution to diversity. To address these issues, we investigated the regulation of the RCO homeobox gene, which contributed to the evolution of complex leaves following its tandem duplication from LMI1. By characterizing seventeen regulatory alleles at the LMI1/RCO locus that we generated by genome editing, we found that the evolved RCO enhancer is subject to pronounced negative regulation that helps delimit the RCO expression domain. While the LMI1 enhancer was strictly required for LMI1 gene expression, the same was not true for the RCO enhancer, which caused only partial loss of function when deleted. We mapped both positively and negatively acting sequences within the RCO enhancer, validated them in reporter gene assays and showed that a repressive sequence arose in association with a nested duplication within the evolved RCO enhancer. This repressive sequence played a key role in shaping the specific RCO expression domain that underlies its role in leaf complexity, and we provide evidence that it helped to prevent potential pleiotropic effects arising from evolutionary diversification or RCO expression. Our findings highlight the regulatory features of a diversity-linked enhancer and show that the evolution of repressive sequences is a powerful force in regulatory evolution.
