Clinging to the walls of tropical caves is a type of plant with a single leaf that continues to grow larger for as long as the plant survives. Researchers at the University of Tokyo hope that their study of this unusual species may help inspire future genetic tools to control the size of common crop plants.
“We are pleased that we finally made a small breakthrough studying this plant,” said Professor Hirokazu Tsukaya, who led the recent research project.
The plant’s scientific name, Monophyllaea glabra, means “hairless species of one-leaf plant.” M. glabra sprouts from a seed with two embryonic leaves called cotyledons, but only one of the cotyledons continues to develop into a leaf.
All Monophyllaea species grow one leaf that, as far as scientists have observed, can continue growing bigger as long as the plant lives. Most plants have no limit on the number of leaves they can grow, but those leaves do have a predetermined maximum size.
Tsukaya first tried working with Monophyllaea in the early 1990s after a trip to see the plants growing in their native habitat in Thailand.
“Monophyllaea like to live in limestone caves in Southeast Asia. If you have a chance to go there, you can see these plants easily,” said Tsukaya.
The same curious biology that made the plants so interesting also made them challenging to study with new genetic tools being designed at the time for more common species with immediate agricultural or medical relevance. After a decadeslong hiatus while other molecular techniques developed, the project to understand Monophyllaea began again recently when doctoral student and first author of the research paper Ayaka Kinoshita joined the lab.
“I believe ours is the only lab in the world currently studying this species,” said Tsukaya.
Understanding what makes Monophyllaea unique required tools that could see the location and activity level of genes early in the leaf’s development. A technique known as whole-mount in situ hybridization allows researchers to preserve whole chunks of an organism, not just thin slices, and lock in place all of the genetic material the cells were using at the time of their death.