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The moss Polytrichum juniperinum showing red stalked sporophyte offspring growing on the parent plants
Photo Credit: Des O'Callaghan
Scientific Frontline: Extended "At a Glance" Summary: WOX Gene Neofunctionalization and Moss Evolution
The Core Concept: A recently re-evaluated moss gene, PpWOX13LC, actively regulates plant reproduction by acting as a genetic brake to limit sporophyte development and ensure efficient parental resource allocation.
Key Distinction/Mechanism: While closely related plant genes (PpWOX13LA and Pp13WOX13LB) promote post-fertilization offspring growth, PpWOX13LC suppresses excess formation. It utilizes novel protein structures to block older growth-promoting proteins, preventing the development of smaller, less viable "twins" or "triplets" on a single shoot.
Major Frameworks/Components:
- WOX Gene Family: A highly conserved family of plant proteins responsible for controlling cellular growth and tissue development.
- Neofunctionalization: The evolutionary mechanism whereby a duplicated gene acquires a completely novel, advantageous function over time.
- Parental Resource Allocation: The biological strategy of limiting offspring quantity to maximize individual offspring size, viability, and successful life cycle progression.
Branch of Science: Evolutionary Biology, Plant Genetics, Molecular Biology, Botany.
Future Application: Deciphering how plants naturally execute genetic suppression of excess fruiting bodies could inform agricultural biotechnology, specifically in engineering crop genetics to optimize resource allocation for robust yields over unviable, excess seed production.
Why It Matters: The discovery underscores that restricting offspring production at the molecular level is a critical evolutionary innovation. It demonstrates how ancient, highly conserved regulatory "brakes" are just as essential for long-term evolutionary success as growth-promoting genes.
A moss gene previously thought to be inactive actually plays a key role in the plant's evolutionary success, researchers from the University of Bristol have discovered.
A new paper published today in Current Biology investigates a family of plant genes called WOX genes—proteins that help control growth and development.
In mosses, two WOX genes (PpWOX13LA and PpWOX13LB) were already known to play an important role in reproduction by supporting the development of the offspring, known as sporophytes, after fertilization.
A third related gene, PpWOX13LC, was previously thought to be inactive, as it appeared incomplete and was not detected in many plant tissues. However, the study showed that this gene is active during reproduction, particularly during the formation of reproductive organs and egg cells.
Professor Jill Harrison from the School of Biological Sciences at the University of Bristol explained, “When we disabled PpWOX13LC, the moss produced extra sporophytes on a single reproductive shoot. This suggests that, unlike its relatives, which encourage sporophyte growth, PpWOX13LC actually acts like a brake, preventing too many sporophytes from developing.”
Further evolutionary analysis found that PpWOX13LC belongs to a large group of similar genes found only in mosses, originating from an ancient gene duplication event. Over time, this duplicated gene appears to have evolved a new function: suppressing excess sporophyte formation. The new proteins feature structures that block the old proteins, preventing too many offspring from developing.
The researchers suggest this new function may have been advantageous; limiting the number of offspring allows the parent plant to allocate resources more efficiently, potentially improving reproductive success.
“Rather than being inactive, our research suggests that the evolution of PpWOX13LC was an important innovation that helped shape moss reproduction and contributed to the long-term evolutionary success of mosses,” said lead author George Greiff, who carried out the research as part of his PhD in the School of Biological Sciences.
“The retention of this trait through hundreds of millions of years demonstrates its importance in the regulation of parental resource allocation during evolution,” he added.
“Without this protein, plants produce more twins and triplets, with each being smaller than solo offspring. This is a disadvantage in mosses, affecting life cycle progression and reproductive success.”
Published in journal: Current Biology
Title: WOX neofunctionalization following an ancient duplication in mosses
Authors: George R.L. Greiff, Max Bethell, James Clark, and C. Jill Harrison
Source/Credit: University of Bristol
Edited by: Scientific Frontline
Reference Number: ebio061826_01
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