Clues as to how plants managed this epic transition can be found in the humble hornwort, a group of unique, often overlooked plants that have remained largely genetically unchanged over the millennia.
New research conducted by Boyce Thompson Institute (BTI) has explored the genetic blueprints of hornworts, uncovering fascinating details about plant evolution and the early days of life on land.
“We began by decoding the genomes of 10 hornwort species, representing all known families within this unique plant group,” said Peter Schafran, a postdoctoral scientist at the BTI and first author of the study. “What we found was unexpected: hornworts have maintained remarkably stable chromosomes despite evolving separately for over 300 million years.”
Unlike many plants, hornworts have not experienced whole-genome duplication (where an organism’s entire genetic material is duplicated). This absence of duplication has resulted in stable “autosomes” — the chromosomes that hold most of an organism’s genetic material — which have remained relatively unchanged across hornworts despite their deep evolutionary history.
However, not all parts of the hornwort genome are so static. The study revealed the presence of “accessory chromosomes”— extra genetic material that isn’t essential for survival but can provide additional benefits. These accessory chromosomes are much more dynamic, evolving rapidly and varying even within individual plants. Additionally, the researchers identified potential sex chromosomes in some species, shedding light on the evolution of plant reproductive strategies.
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The study, recently published in Nature Plants, also provided insights into specific plant traits. For example, the researchers uncovered new information about genes involved in flavonoid production (pigments that protect against UV radiation), stomata formation (tiny pores that regulate gas exchange), and hormone signaling. These findings help refine our understanding of how early land plants adapted to their new, challenging environment.
Through their hornworts study, the research team has developed a resource to help scientists comprehend how life on Earth has evolved. It also provides insights into how plants might adapt to future environmental challenges.
In another recent study, fellow researchers at the BTI have investigated how hornworts' supreme photosynthesizing capabilities hold clues for boosting crop efficiency.
"Hornworts possess a remarkable ability that is unique among land plants: they have a natural turbocharger for photosynthesis," said Tanner Robison, a graduate student at BTI and first author of the paper published in Nature Plants. "This special feature, called a CO₂-concentrating mechanism, helps them photosynthesize more efficiently than most other plants, including our vital food crops."
"It's like finding a simpler, more efficient engine design," explained Fay-Wei Li, co-author of the study. "This simplicity could make it easier to engineer similar systems in other plants, like essential crops."
The potential impact is substantial. The research team estimates that installing a similar CO₂-concentrating mechanism in crops could boost photosynthesis by up to 60%, leading to significant increases in yields without requiring more land or resources.
As we face the dual challenges of climate change and food security, this tiny plant might hold the key for meaningful farming innovation.