A team of scientists from the ARC Centre of Excellence for Plant Success in Nature and Agriculture at Monash University has identified a single gene in a land plant that could help explain how plants first evolved the ability to grow continuously, a key trait that allowed them to colonise dry land and shape life on Earth.
Published in Current Biology, the study focuses on Marchantia polymorpha, a liverwort whose ancestors diverged from flowering plants more than 400 million years ago.
Despite its small size, this humble plant harbours a genetic mechanism that appears to have been critical for the early evolution of land plants.
The gene, called MpARF2, acts as a master regulator of stem cells, the undifferentiated cells responsible for ongoing growth.
According to the researchers, MpARF2 creates a protective zone within the plant where growth can be safely coordinated, shielding stem cells from signals that would otherwise promote differentiation.
“The pool of stem cells creates a meristem, from which all organs of plants are derived,” said Dr Eduardo Flores-Sandoval, lead author from the School of Biological Sciences at Monash University.
“The evolution of meristems allowed plants to grow directionally in response to environmental cues, such as light and gravity, an important facet as they are literally rooted to a spot.”
The study also found that MpARF2 plays a dual role, not only blocking sensitivity to the plant hormone auxin (which drives differentiation) but also promoting the local production of auxin itself.
This feedback system allows the plant to both produce and resist growth signals at the same time, depending on location.
“It’s a beautifully simple, elegant mechanism,” said Professor John Bowman, senior author on the paper.
“The stem cells both produce a signal, auxin, but are immune to the effects of the signal due to MpARF2, and thus the stem cells act as an organizer that instructs adjacent cells to begin the differentiation pathway,” he said.
“It’s likely this mechanism was a crucial innovation in the earliest land plants, with meristems allowing directional growth in response to environmental cues and being able to regenerate if the original meristems are consumed by herbivores.”
The findings deepen our understanding of plant evolution and could have implications for modern agriculture and climate resilience, particularly in designing crops with improved regeneration or stress responses.
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