Receptors for neuron communication in humans vital for reproduction in mosses

July 24, 2017, University of Maryland
P. patens, the moss used for the study, growing in the laboratory. Credit: Jörg Becker, Instituto Gulbenkian de Ciência.

Glutamate receptors play a central role in the human nervous system. Scientists estimate 90 percent of the human brain's synapses, or connections between neurons, send signals using glutamate. The role of similar receptors in plants, which do not have a nervous system, is not fully understood.

A new study led by Jose Feijo, professor of and molecular genetics at the University of Maryland, revealed two previously unknown roles for glutamate receptor-like proteins in : controlling the navigation of to locate eggs and regulating the development of fertilized eggs. This work was published in the journal Nature on July 24, 2017.

"Scientists have shown that plants' glutamate receptor-like proteins play a role in pollen tube growth and defense against pathogens, but we discovered completely novel functionalities for these receptors that no one has ever observed before," Feijo said. "Since glutamate receptors were thought to act in neural transmission and essentially nothing else, no one knows why plants would have so many copies of these genes. It is very exciting to find that such genes may have been conserved during plant evolution to mediate cell-to-cell communication in sexual reproduction."

Feijo and his collaborators tested the function of glutamate receptor-like proteins in the moss Physcomitrella patens because it contains only two genes that encode for these proteins. The popular plant model Arabidopsis thaliana, on the other hand, contains 20 glutamate receptor-like genes.

After the researchers removed the two glutamate receptor-like genes from P. patens by mutation, the mosses grew normally, but did not reproduce. The reason: the mutant plants' sperm did not reach the archegonia, the female organ that contains eggs for fertilization and secretes a chemical signal to attract sperm.

While normal sperm twisted and tumbled and took sharp turns to find the archegonia entrance, mutant sperm swam normally but did not change direction to reach the eggs. In addition, normal sperm could find the archegonia of mutated plants, while mutated sperm could not locate normal archegonia. Together, these findings suggest that sperm require glutamate receptor-like proteins to translate the archegonia's signal.

On the left, wild-type (normal) P. patens sperm (in red circle) swim toward the archegonia, eventually finding and entering the egg-containing organ. On the right, mutant sperm (green circle) swims but does not approach the archegonia. Credit: Carlos Ortiz-Ramírez, Instituto Gulbenkian de Ciência
"This is important because glutamate receptors are actually present on many non-neuronal tissues in the human body, including sperm, but the reason is unclear," Feijo said. "Our results suggest one answer, which is that glutamate receptors on swimming sperm may be evolutionarily conserved."

In some mutant plants, sperm found the archegonia by chance, fertilized eggs and created spores, but the spores died shortly thereafter. The researchers found that the did not produce BELL1, a needed for development. Supplying BELL1 to the mutant spores led to normal plant development. The results suggest that glutamate receptor-like proteins regulate the production of BELL1 protein, possibly as a second control point of fertilization.

Feijo and his collaborators also investigated how the moss -like protein might be conducting a signal in plants. They found that it behaves as a channel that allows calcium ions to flow through it. Many human glutamate receptors function in the same way, suggesting that both the plant and the human versions of the receptor conserved this function during parallel evolution.

Going forward, Feijo plans to search for the signaling molecule of the plant receptor, which he believes is not . In addition, having demonstrated that an important neuronal receptor is related to a receptor in moss, Feijo is enthusiastic about the potential of using plants to study neuronal functions.

"It's difficult to study these in humans because of the complexity as well as ethical issues," Feijo said. "But if we can study them in a plant context, we may get answers about fundamental cell biology that could help us understand much more complex functions, such as memory, learning or neurodegenerative diseases."

The research paper, "Glutamate Receptor-like channels are essential for chemotaxis and reproduction in mosses," Carlos Ortiz-Ramirez, Erwan Michard, Alexander Simon, Daniel Damineli, Marcela Hernandez-Coronado, Jorg Becker and Jose Feijo, was published online in the journal Nature on July 24, 2017.

Explore further: Research team discovers new kind of signalling mechanism in plant cells

More information: Carlos Ortiz-Ramírez et al, Glutamate receptor-like channels are essential for chemotaxis and reproduction in mosses, Nature (2017). DOI: 10.1038/nature23478

Related Stories

An amino acid controls plants' breath

December 6, 2016

Plants breathe and "sweat" through stomata, microscopic pores found on leaves, stems and other plant organs. Through the stomata, plants take up carbon dioxide for photosynthesis and breathe out the products of this process, ...

Recommended for you

In colliding galaxies, a pipsqueak shines bright

February 20, 2019

In the nearby Whirlpool galaxy and its companion galaxy, M51b, two supermassive black holes heat up and devour surrounding material. These two monsters should be the most luminous X-ray sources in sight, but a new study using ...

Research reveals why the zebra got its stripes

February 20, 2019

Why do zebras have stripes? A study published in PLOS ONE today takes us another step closer to answering this puzzling question and to understanding how stripes actually work.

When does one of the central ideas in economics work?

February 20, 2019

The concept of equilibrium is one of the most central ideas in economics. It is one of the core assumptions in the vast majority of economic models, including models used by policymakers on issues ranging from monetary policy ...

Correlated nucleons may solve 35-year-old mystery

February 20, 2019

A careful re-analysis of data taken at the Department of Energy's Thomas Jefferson National Accelerator Facility has revealed a possible link between correlated protons and neutrons in the nucleus and a 35-year-old mystery. ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.