Over 450 million years ago, life began a remarkable transformation as plants made the monumental leap from aquatic environments to dry land. This transition was pivotal in Earth’s history, reshaping ecosystems and paving the way for terrestrial life as we know it. Among the earliest pioneers were the ancestors of hornworts, a small and ancient group of plants that remain relatively unassuming but scientifically fascinating today. Recent research has delved into the genetic makeup of hornworts, unlocking profound insights into plant evolution and the adaptations that enabled life to flourish on land.
A groundbreaking study led by researchers at the Boyce Thompson Institute (BTI) has focused on decoding the genomes of ten hornwort species, representing all known families within this unique plant group. The research, published in Nature Plants, offers a glimpse into the evolutionary strategies of hornworts and their ability to adapt over hundreds of millions of years. According to Peter Schafran, a postdoctoral scientist at BTI and first author of the study, the findings were unexpected and illuminating. “We discovered that hornworts have maintained remarkably stable chromosomes despite having evolved separately for over 300 million years,” Schafran noted. This stability, a hallmark of their genetic evolution, offers clues about the broader mechanisms of plant genome organization.
Unlike many plants that have undergone whole-genome duplication—where the entirety of an organism’s genetic material is duplicated—hornworts have remained genetically streamlined. This absence of duplication has led to the stability of their primary chromosomes, or autosomes, which contain the majority of an organism’s genetic instructions. Remarkably, despite their divergence from other plant lineages, these chromosomes have remained largely unchanged over the millennia, preserving a consistent genetic blueprint that underscores hornworts’ evolutionary resilience.
Yet, not all aspects of the hornwort genome exhibit such stasis. The research revealed the presence of accessory chromosomes, an intriguing genetic feature. Accessory chromosomes contain extra DNA that isn’t critical for survival but often confers advantageous traits. These chromosomes are dynamic, evolving rapidly and exhibiting variation even among individuals within the same species. This genetic flexibility may have provided hornworts with the adaptability to thrive in diverse environments, including the harsh and changing conditions that characterized early terrestrial landscapes.
Another groundbreaking aspect of the study was the identification of potential sex chromosomes in certain hornwort species. This discovery sheds light on the evolution of plant reproductive strategies. Sex chromosomes are relatively uncommon in plants, and their presence in hornworts suggests early and varied approaches to reproduction during the evolution of land plants. These findings could help explain how early plants diversified their reproductive mechanisms to succeed on land.
Beyond these evolutionary insights, the study has contributed to our understanding of how specific genetic traits facilitated the adaptation of plants to terrestrial environments. For instance, researchers identified genes involved in the production of flavonoids, pigments crucial for protecting plants against ultraviolet (UV) radiation—a hazard that became significant as plants ventured out of the water and under direct sunlight. Similarly, the genetic basis of stomata formation was examined. Stomata are microscopic pores that play a vital role in regulating gas exchange, allowing plants to balance water retention and carbon dioxide absorption in a fluctuating climate.
The researchers also investigated genes related to hormone signaling pathways, which are essential for regulating growth and responding to environmental stimuli. These findings not only refine our understanding of hornworts but also enhance our broader comprehension of plant physiology and the evolutionary adaptations necessary for life on land. By analyzing these genetic features, scientists can better grasp how early plants managed to establish themselves in a challenging new environment and gave rise to the diverse terrestrial flora we see today.
One of the most notable aspects of this research was the comprehensive sequencing effort undertaken by the team. The ten hornwort species sequenced in this study represent the most extensive genetic dataset of any plant group relative to its total number of species. This exhaustive approach provides an unprecedented resource for understanding plant evolution, not just within hornworts but across all lineages of land plants.
The team’s creation of a “pan-phylum” genetic dataset for hornworts marks a significant milestone. This dataset enables researchers to trace the genetic innovations that underpin some of the most important evolutionary events in plant history. Such a resource is invaluable for addressing questions about how plants might respond to future environmental changes, including shifts in climate, soil conditions, and interactions with other organisms. Additionally, it offers a blueprint for using plant genetics to engineer more resilient crops, with implications for agriculture and global food security.
The study also underscores the importance of studying a wide diversity of organisms, not just well-established model species like Arabidopsis thaliana or crop plants. “Our research demonstrates the importance of studying diverse organisms,” explained Fay-Wei Li, associate professor at BTI and lead author of the study. “By expanding our knowledge of hornworts, we gain a more complete picture of plant evolution and the incredible diversity of life on our planet.” The choice to focus on hornworts, a relatively overlooked group, highlights the need for a broader approach in biological research, which often centers on a few species with extensive historical datasets.
Hornworts may appear unremarkable at first glance—small, simple plants growing in damp environments—but they offer profound lessons about the resilience, adaptability, and innovation inherent in life. Their ability to maintain stable genomes while incorporating dynamic accessory chromosomes reflects a balance of conservation and flexibility that has likely contributed to their survival across geological epochs.
The study’s findings also emphasize the interplay between genetic stability and adaptability. While hornwort autosomes have remained consistent, the dynamic nature of their accessory chromosomes suggests that genetic variability and modularity play crucial roles in survival and adaptation. These features may have given hornworts an edge in navigating early terrestrial ecosystems and establishing a foothold in environments fraught with challenges like desiccation, UV exposure, and nutrient scarcity.
The implications of this research extend beyond hornworts. By shedding light on the genetic strategies that facilitated the colonization of land, it offers insights into the broader processes of evolution, adaptation, and resilience. It also underscores the value of integrating modern genetic tools with the study of ancient lineages, creating new opportunities to understand life’s history and future potential.
As humanity faces unprecedented environmental changes, the lessons drawn from early plants like hornworts become ever more relevant. Their genetic blueprints may inspire innovations in agriculture, conservation, and biotechnology, helping us design solutions that draw on nature’s own adaptive strategies. This research not only enhances our scientific knowledge but also reminds us of the enduring complexity and ingenuity of life on Earth—a legacy that began with small, humble pioneers over 450 million years ago.
Reference: Peter Schafran et al, Pan-phylum genomes of hornworts reveal conserved autosomes but dynamic accessory and sex chromosomes, Nature Plants (2025). DOI: 10.1038/s41477-024-01883-w