A moss gene previously thought to have been inactive actually plays a key role in their evolutionary success, researchers from the University of Bristol have discovered.
The new paper published in Current Biology today [18 June] has investigated a family of plant genes called WOX genes - proteins which help control growth and development.
In mosses, two WOX genes (PpWOX13LA and Pp13WOX13LB) were already known to play an important role in reproduction by supporting the development of the offspring, known as sporophytes, after fertilisation.
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 only found 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, with the new proteins featuring structures that block the old proteins, preventing too many offspring from developing.
The researchers suggest this new function may have been advantageous, as 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."
Paper
'WOX neofunctionalisation following an ancient duplication in mosses by G. Greiff, M. Bethell, J. Clark, and J. Harrison in Current Biology
