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ST. LOUIS, MO – January 29, 2015 – Daniel Chitwood, Ph.D., assistant member, and his research group at the Donald Danforth Plant Science Center’s in St. Louis, in collaboration with the laboratory of Neelima Sinha, Ph.D., at the University of California, Davis, are using the world’s largest single-celled organism, an aquatic alga called Caulerpa taxifolia, to study form and function in plants. They recently reported the results of their work in the journal,PLOS Genetics.
“Caulerpa is a unique organism,” said Chitwood. “It’s a member of the green algae, which are plants. Remarkably, it’s a single cell that can grow to a length of six to twelve inches. It independently evolved a form that resembles the organs of land plants. A stolon runs along the surface that the cell is growing on and from the stolon arise leaf-like fronds, and root-like holdfasts, which anchor the cell and absorb nutrients. All of these structures are just one cell.”
“For many years, I’ve been interested in structure and form in plants, especially in tomato,” Chitwood continued. “As you might imagine, finding out what determines something like leaf shape in a complex tomato plant is challenging. But the benefits of understanding how plant structure relates to productivity of our important crops are potentially large. Plants like tomato or rice have tremendous complexity because they have billions of cells that are specialized to form different tissues and organs, like roots. Caulerpa is the size of a plant and has highly specialized organs that serve unique functions, yet is contains just one giant cell. How does that happen?”
Chitwood and his group reasoned that the structure of Caulerpa might be governed by which genes are active in various parts of the cell. This would be reflected by the composition of RNA in different Caulerpa structures. (RNAs are the molecular products found when genes are expressed or “turned on.”) For example, the frond part of the cell might show different RNA’s from the holdfast part of the cell. Such a result would shed light on the genes necessary to make the specialized structure, or to make that structure work properly.
“The results turned out to be even more interesting than we’d hoped,” said Chitwood. “Not only do different parts of the Caulerpa cell show different RNA’s, but there is also some correlation between RNA’s that are expressed together within different parts of the Caulerpa cell with those expressed together in the multicellular organs of tomato. Even though Caulerpa is seperated from land plants by more than 500 million years of evolution, in many ways Caulerpa displays patterns of RNA accumulation shared with land plants today.”
“Our work on Caulerpa has given us a whole new way of thinking about plant structure and development,” Chitwood continued enthusiastically. “It’s clear that the basic form we associate with land plants can arise with and without multicellularity. In fact, because higher plant cells are actually connected to each other by channels (termed plasmodesmata), could we really think of higher plants, like tomato, more like a single cell instead of a multitude of cells? This idea is consistent with our observations of a shared pattern of RNA accumulation. Frankly, our results have caused us to think about plant structure from an entirely different perspective, which is the most important outcome from this research.”
About The Donald Danforth Plant Science Center
Founded in 1998, the Donald Danforth Plant Science Center is a not-for-profit research institute with a mission to improve the human condition through plant science. Research aims to feed the hungry and improve human health, preserve and renew the environment and position the St. Louis region as a world center for plant science. The Center’s work is funded through competitive grants and contract revenue from many sources, including the National Institutes of Health, U.S. Department of Energy, National Science Foundation, U.S. Department of Agriculture, U.S. Agency for International Development, the Bill & Melinda Gates and Howard G. Buffett Foundations.
To keep up to date with Danforth Center’s current operations and areas of research, please visit, www.danforthcenter.org, featuring information on Center scientists, news, and the “Roots & Shoots” blog. Follow us on Twitter at @DanforthCenter.