The gene that determines plant sex

Scientists have discovered a gene responsible for determining the sex of a plant. Their study is the culmination of three decades of genetic work with a fern species, coupled with the latest molecular and physiological techniques for gene characterisation, protein function and plant behaviour.

The research team, led by the University of Tasmania (UTAS) and featuring scientists from the University of Würzburg and Purdue University, set out to characterise a fern gene essential for the perception of a sex-determining hormone. They found that through the gene GAIA1, hormones are able to control the sex of plants.

“In animals like humans, X and Y chromosomes make a person male or female, but in ferns a hormonal balance in a one-day-old plant sets maleness or femaleness and we previously had no idea how,” said study co-author Dr Scott McAdam, from the UTAS School of Biological Sciences.

“We now know of a gene that regulates sex by hormone perception and that it has done this for a very long time — at least 370 million years, from when our ancestors were still fish.”

The team additionally discovered that plants have evolved additional uses for this perception pathway, including the control of seed dormancy (essential for an even germination of crops) and the control of excessive plant water loss (essential for plants growing in dry environments). Dr McAdam noted, “This evolutionary change means that this gene is used by every one of our most important crop and forest species to survive during drought or on hot days.

“Last spring and summer, Tasmania experienced an extreme drought, and the subsequent fires destroyed huge areas of rainforest. If it wasn’t for this hormone perception gene stopping the remaining plants in these forests from losing all of their water reserves, Tasmania would now be a desert.”

Published in the journal Proceedings of the National Academy of Sciences, the team’s breakthrough could provide a boost for agriculture and forestry. According to Dr McAdam, “Understanding how these plant processes operate at a genetic level provides the critical first step towards making major improvements to drought tolerance in crop and forest species, or more ideal sex ratios in crops that produce both male and female flowers.”