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These plants have maintained genetic stability for 350 million years

In a study that challenges our understanding of plant evolution, an international team of researchers has discovered stunning genetic stability in lycophytes, one of the oldest groups of land plants.

Slow genetic journey 

Lycophytes, resembling ferns in their appearance, have been part of Earth’s flora for over 350 million years, witnessing the rise and fall of countless species. 

Yet, in a world where change is the only constant, these plants present an anomaly. They have maintained a remarkably consistent genetic structure throughout their extensive history, diverging from the common narrative of plant genetics.

“The exceptionally slow pace of genomic evolution sets these plants apart,” said study senior author Dr. Fay-Wei Li, a professor at the Boyce Thompson Institute. “Understanding why these plants have changed so little could reveal important aspects of plant evolution and genetics.”

Unraveling the mystery 

In their quest to unravel this mystery, the researchers analyzed the genomes of two lycophyte species: Huperzia asiatica and Diphasiastrum complanatum. 

These species, having branched off from a common ancestor around 350 million years ago – a time coinciding with amphibians’ first steps on land – presented a fascinating case study. 

Remarkable genetic stability 

What the researchers found was astonishing. Approximately 30% of the genes in the plants have remained in the same arrangement since their divergence. This phenomenon, known as synteny, signifies an unusual pattern of genetic stability that is rarely seen in the plant kingdom.

“This study opens a window into the past, showing us how remarkably stable the genetic makeup of these plants has been. It’s like finding a living fossil at the genetic level,” said study co-author Dr. Li Wang.

Retention of duplicated genes

Another intriguing aspect observed by the scientists was the retention of duplicated gene copies following whole genome duplication events. Typically, in the aftermath of such events, a handful of duplicate genes may evolve new functions, but the majority are lost through a process called diploidization. 

However, the homosporous lycophytes, a group of seedless vascular plants to which H. asiatica and D. complanatum belong, defied this norm. They retained both sets of genes with relatively few alterations, even after hundreds of millions of years.

Dr. David Wickell, a postdoctoral researcher and co-first author of the study, explained this unique retention of duplicated genes, highlighting its rarity and significance in understanding plant evolution.

Fundamental questions 

The research not only sheds light on the genetic odyssey of lycophytes but also raises fundamental questions about the forces shaping plant evolution. 

Why have these plants maintained genetic stability for so long? What can their unique evolutionary path tell us about the broader processes at play in the plant kingdom?

Study implications 

“That homosporous lycophytes have retained so many duplicate genes and so much synteny is fascinating, a little bit surprising, and doesn’t necessarily fit with our traditional ideas of how genomes reorganize themselves after a large-scale duplication,” noted Dr. Wickell. 

“While it’s still unclear precisely what is driving this difference, we believe that further study of homosporous plants has the potential to provide novel insights into plant genetics and evolution across all land plants. It also underscores the importance of preserving biodiversity, as these amazing plants hold vital clues to the history of life on Earth.”

The study is published in the journal Proceedings of the National Academy of Sciences.

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