Monophyllaea – Plant living with only one leaf

A type of plant has only one lead which grows in the walls of tropical caves. The single leaf continues to grow larger as long as the plant survives. A group of researchers from the University of Tokyo studies this unusual species. They said that this might help inspire future genetic tools to control the size of common crop plants.

Professor Hirokazu Tsukaya, who led this project, said that they finally made a small breakthrough studying this plant. Frontiers in Plant Science published this study.

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One leaf plant

Monophyllaea glabra  is the botanical name of the plant which means “hairless species of one-leaf plant.” Moreover, it sprouts out from seed with two embryonic leaves called cotyledons, but only one of the cotyledons grow into a leaf.

According to scientists observation, all Monophyllaea species grow only one leaf. But this can continue to grow bigger as long as the plant lives. Most of the plants don’t have a limit on the number of leaves they mature, but they do have a predetermined maximum size.

Each leaf is a separate plant
Each leaf is a separate plant

Study on Monophyllaea

In the early 1990s, when Tsukaya went on a trip to see the plants growing in their native habitat in Thailand. At that time only he first tried working with Monophyllaea.

The same plant which is so interesting made them challenging to study the plant with new genetic tools designed at the time to explore common plants. After the development of new molecular techniques, the project to understand Monophyllaea began again recently. This project happened when the doctoral student and first author of the research Ayaka Kinoshita joined the lab.

Tsukaya believed that their lab is the only lab in the world currently studying this species.

Hirozaku Tsukaya
Hirozaku Tsukaya

New tool to explore Monophyllaea

To understand what makes Monophllaea unique, they required tools to see the location and activity level of genes early in the leaf’s development. Whole-mount in situ hybridization is a technique which allows the researchers to preserve whole chunks of an organism and not just thin slices. It locks in place all of the genetic material the cells were using at the time of their death. Moreover, the technique is commonly used in animal tissue. But when it comes to plants, it shows complications because of the stiff outer cell wall around plant cells.

Tsukaya said that luckily they got Assistant Professor Hiroyuki Koga, another member of their lab. He is a professional at using the whole-mount system. Moreover, he is persistent in developing a suitable method for plants. Koga developed a technique to preserve entire three-week-old Monophyllaea plants, and he is the second author of the paper.

Genetic level study of Monophllaea

The normal anatomy in plants cells express the gene SHOOT MERISTEMLESS (STM) at growing tips of stems, referred to as the shoot meristem. Additionally, in young leaves, a gene ANGUSTIFOLIA3 (AN3) promote the multiplication of cells that form the leaf.

Tsukaya said that with their naked eye they couldn’t see any shoot meristem in Monophyllaea. So they planned to find whether it is lost or modified.

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What does the single leaf represent?

Instead of separating the location and timing of the two genes (STM and AN3) expression, the young Monophyllaea overlapped the expression of two genes. The single leaf in the species is actually the combination or fusing of the shoot meristem and leaf.

Tsukaya said that the expression areas in this species overlap. So this plant is a hybrid of an ordinary leaf and shoot meristem. He added that this gene expression pattern might be one of the reasons for the plant’s curious appearance.

Furthermore, this study helps to understand how unusual species like Monophyllaea glabra evolved to use common genes in uncommon ways. Moreover, this could help agricultural scientists to develop new tools for controlling the size of leaves results in optimal cultivation.

In summary, Tsukaya said that the characteristics of Monophllaea are very unique. Moreover, dealing with the unique phenomenon provides new insights to plant science.

 

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